1. The Study Of Nature Is Essential To Happiness
In contrast to Socrates, Epicurus emphasized that the study of natural science is essential to happiness. This is not because natural science is intrinsically interesting or academically valuable, but because it is the only reliable instrument for removing the three great sources of groundless fear that destroy happiness: fear of the gods' involvement in natural events and human affairs, fear of death and what follows it, and fear of fate or necessity. Without natural philosophy, we are left with mythology -- which has reliably generated anxiety across all human cultures. With it, we can demonstrate that the gods are blessed and undisturbed beings who take no interest in human affairs, that death is simply the end of sensation with no subsequent suffering, and that human beings have genuine freedom of choice. These demonstrations are not mere intellectual conclusions: they are the therapeutic core of Epicurean philosophy. Epicurus's own enormous output -- Diogenes Laertius reports he surpassed all other philosophers in the number of books he composed -- reflects how urgently he regarded the communication of this understanding as a practical necessity, not a scholarly exercise.
Wherefore since the method I have described is valuable to all those who are accustomed to the investigation of nature, I who urge upon others the constant occupation in the investigation of nature, and find my own peace chiefly in a life so occupied, have composed for you another epitome on these lines, summing up the first principles of the whole doctrine. (Bailey)
But what falls within the investigation of risings and settings and turnings and eclipses, and all that is akin to this, is no longer of any value for the happiness which knowledge brings, but persons who have perceived all this, but yet do not know what are the natures of these things and what are the essential causes, are still in fear, just as if they did not know these things at all: indeed, their fear may be even greater, since the wonder which arises out of the observation of these things cannot discover any solution or realize the regulation of the essentials. (Bailey)
All these things, Pythocles, you must bear in mind; for thus you will escape in most things from superstition and will be enabled to understand what is akin to them. And most of all give yourself up to the study of the beginnings and of infinity and of the things akin to them, and also of the criteria of truth and of the feelings, and of the purpose for which we reason out these things. For these points when they are thoroughly studied will most easily enable you to understand the causes of the details. But those who have not thoroughly taken these things to heart could not rightly study them in themselves, nor have they made their own the reason for observing them. (Bailey)
Were we not upset by the worries that celestial phenomena and death might matter to us, and also by failure to appreciate the limits of pains and desires, we would have no need for natural philosophy. (tr. Long & Sedley)
There is no way to dispel the fear about matters of supreme importance, for someone who does not know what the nature of the universe is but retains some of the fears based on mythology. Hence without natural philosophy there is no way of securing the purity of our pleasures. (tr. Long & Sedley)
There is no benefit in creating security with respect to men while retaining worries about things up above, things beneath the earth, and generally things in the infinite. (tr. Long & Sedley)
I would rather speak with the frankness of a natural philosopher, and reveal the things which are expedient to all mankind, even if no one is going to understand me, than assent to the received opinions and reap the adulation lavishly bestowed by the multitude. (tr. Long & Sedley)
Natural philosophy does not make people boastful and loud-mouthed, nor flaunters of culture, the thing so hotly competed for among the multitude, but modest and self-sufficient, and proud at their own goods, not at those of their circumstances. (tr. Long & Sedley)
(1) When human life lay foul to see and groveling upon the ground, crushed by the weight of Religion, who displayed her head from the regions of heaven, lowering over mortals with horrible aspect, (2) a man of Greece dared first to raise his mortal eyes against her, first to make a stand against her; for neither fables of the gods could quell him, nor thunderbolts, nor heaven with menacing roar, but all the more they goaded the eager courage of his soul to long to be the first to burst through the close-set bolts of nature's gates. (3) Therefore his vigorous mind won through, and he passed on far beyond the fiery walls of the world, and in mind and spirit traversed the boundless universe; (4) whence returning victorious he reports to us what can arise, what cannot, and by what principle each thing has its powers limited and its deep-set boundary stone. (5) Therefore Religion is now in turn cast down and trampled underfoot, while we by the victory are exalted high as heaven. (tr. Long & Sedley)
Fr. 4 ... [as is supposed by] some of the philosophers and especially the Socratics. They say that pursuing natural science and busying oneself with investigation of [celestial phenomena] is superfluous and unprofitable, and they do [not even] deign [to concern themselves with such matters.] Fr. 5 [Others do not] explicitly [stigmatise] natural science as unnecessary, being ashamed to acknowledge [this], but use another means of discarding it. For, when they assert that things are inapprehensible, what else are they saying than that there is no need for us to pursue natural science? After all, who will choose to seek what he can never find? Now Aristotle and those who hold the same Peripatetic views as Aristotle say that nothing is scientifically knowable, because things are continually in flux and, on account of the rapidity of the flux, evade our apprehension. We on the other hand acknowledge their flux, but not its being so rapid that the nature of each thing [is] at no time apprehensible by sense-perception. And indeed [in no way would the upholders of] the view under discussion have been able to say (and this is just what they do [maintain] that [at one time] this is [white] and this black, while [at another time] neither this is [white nor] that black, [if] they had not had [previous] knowledge of the nature of both white and black.
Practise these things and the things akin to them day and night by yourself and with someone like yourself, and you will never be disquieted awake or asleep, but will live like a god among men. For a man who lives among immortal goods is utterly unlike a mortal creature. (Bailey)
O thou who first amid such murky darkness didst raise aloft so bright a light, illuminating the blessings of life, thee I follow, glory of the Greek nation, and in thy deep footprints now I plant my own, not so much eager to rival thee as for love's sake, since the swallow contends not with the swan, nor can kids with staggering legs compete in speed with the strong horse. Thou, father, art discoverer of things; thou suppliest us with a father's precepts; and like bees on flowery meadows we feed from thy pages, feeding on thy golden words, golden and ever worthy of everlasting life. For as soon as thy philosophy, born from thy godlike mind, begins to proclaim the nature of things, the terrors of the mind are dispersed, the walls of the world part asunder, I see things moving on through all the void. (Bailey)
He surpassed all in the multitude of his writings, filling as he did some three hundred volumes with his own work, containing not a single citation from other writers, but his own views throughout. (Bailey)
For once that philosophy which arose in your godlike mind has begun to speak about the nature of things, then terrors in the mind disperse, the world's walls fall open, I see what is going on in all the void, the majesty and calm habitations of the gods reveal themselves in places where no winds disturb, no clouds bring showers, no white snow falls congealed with bitter frost to harm them, the always cloudless aether vaults above, and they smile, as far and as wide as the light spreads out. Godlike pleasure and awe take hold of me up there with these things, to think that nature, through your genius, is laid out so clearly, so openly exposed on every side. (Johnston)
Furthermore, we must believe that to discover accurately the cause of the most essential facts is the function of the science of nature, and that blessedness for us in the knowledge of celestial phenomena lies in this and in the understanding of the nature of the existences seen in these celestial phenomena, and of all else that is akin to the exact knowledge requisite for our happiness. (Bailey)
Here, Herodotus, is my treatise on the chief points concerning the nature of the general principles, abridged so that my account would be easy to grasp with accuracy. I think that, even if one were unable to proceed to all the detailed particulars of the system, he would from this obtain an unrivaled strength compared with other men. For indeed he will clear up for himself many of the detailed points by reference to our general system, and these very principles, if he stores them in his mind, will constantly aid him. For such is their character that even those who are at present engaged in working out the details to a considerable degree, or even completely, will be able to carry out the greater part of their investigations into the nature of the whole by conducting their analysis in reference to such a survey as this. And as for all who are not fully among those on the way to being perfected, some of them can from this summary obtain a hasty view of the most important matters without oral instruction so as to secure peace of mind. (Bailey)
For he who said -- "Verily first created of all was Chaos; thereafter Earth broad-bosom'd, of all things the seat" -- is refuted by himself; for if someone asks him "from what did Chaos come into being?," he will have no answer. And this, as some say, was the reason why Epicurus took to philosophizing. For when still quite a youth he asked his schoolmaster, who was reading out the line "Verily first created of all was Chaos," what Chaos was created from, if it was created first. And when he replied that it was not his business, but that of the men called philosophers, to teach things of that sort, "Well then," said Epicurus, "I must go off to them, if it is they who know the truth of things." (Bury)
2. Nothing Comes From Nothing Or Goes To Nothing
The observation that nothing comes from nothing -- or as Epicurus states in the Letter to Herodotus, that nothing comes into being from what does not exist -- is the starting point and foundation of all Epicurean reasoning about nature. If things could arise from nothing, anything could produce anything with no need for seeds or prior causes. The companion principle, that nothing is destroyed into nothing, follows from the same logic: if things could go to nothing, everything would eventually vanish with no possibility of renewal. Together these two observations establish that the universe is self-sustaining, eternal, and entirely natural in its operations.
This conclusion is reached by deductive reasoning from observations that our senses can make, even though the atoms themselves -- from which things come and to which they return -- are not directly perceivable. In the Letter to Herodotus and throughout Lucretius' On the Nature of Things, these principles serve as the foundation of a chain of reasoning that leads to the conclusion that the universe is neither created nor supervised by supernatural forces. They also carry the direct practical implication that fear of supernatural punishment and fear of absolute annihilation after death are both groundless -- neither threatening gods nor absolute nothingness await us. This is not an abstract curiosity: the study of nature is necessary to remove these fears, and removing them is in turn necessary to attain complete pleasure.
Having grasped these points, we must now observe, concerning the non-evident, first of all that nothing comes into being out of what is not. For in that case everything would come into being out of everything, with no need for seeds. Also, if that which disappears were destroyed into what is not, all things would have perished, for lack of that into which they dissolved. Moreover, the totality of things was always such as it is now, and always will be, since there is nothing into which it changes, and since beside the totality there is nothing which could pass into it and produce the change. (tr. Long & Sedley)
For if things came into being out of nothing, every species would be able to be produced out of everything, nothing would need a seed. Men, to start with, would be able to spring up out of the sea and scaly fish from the land, and birds hatch out of the sky. Cattle and other livestock, and every species of wild animal, would be born at random and occupy farmland and wilderness alike. Nor would the same fruits stay regularly on the same trees, but would change over: all trees would be able to bear everything. In a situation where each thing did not have its own procreative bodies, how could there be a fixed mother for things? But since in fact individual things are created from fixed seeds, each is born and emerges into the realm of daylight from a place containing its own matter and primary bodies; and the reason why everything cannot come into being out of everything is that particular things contain their own separate powers. (tr. Long & Sedley)
Again, if time totally destroys the things which it removes through age, and consumes all their material, from where does Venus bring back living creatures, each after its species, to the daylight of life? Or from where, thereafter, does the creative earth nourish them and make them grow by supplying each species with its food? From where do internal springs, and rivers flowing from afar, replenish the sea? From where does the aether feed the stars? For infinite time past ought to have consumed those things whose body is perishable. But if in that expanse of time past there have been bodies out of which this sum of things is reconstituted, they are indeed endowed with an imperishable nature. Therefore it cannot be that all things are reduced to nothing. (tr. Long & Sedley)
For if something changes and leaves its boundaries, that is immediately the death of the thing that it previously was. (tr. Long & Sedley)
Again, if time destroys entirely whatever things it removes in advanced age, consuming all material, from where does Venus restore the races of animals back into the light of life? Or once restored, from where does the creative earth nourish and increase them, supplying food according to their kind? From where do native springs and rivers afar replenish the sea? From where does aether feed the stars? For infinite ages past must have consumed all things that have a mortal body. But if in all that long time past those bodies have existed from which this sum of things is refreshed and renewed, they are indeed endowed with an immortal nature. Therefore things cannot be reduced to nothing. And again, one and the same force and the same cause would destroy all things equally, unless an eternal matter held them together. For a touch would be enough to bring destruction, seeing there would be no body of eternal substance to dissolve. But as things are, because the fastenings of matter are one with another of different kinds, and its substance is eternal, things remain whole and unharmed, until a force strong enough to overcome their constitution comes against them. (Bailey, adapted)
Moreover, the totality of things was always such as it is now, and always will be, since there is nothing into which it changes, and since beside the totality there is nothing which could pass into it and produce the change. (tr. Long & Sedley)
Fear forsooth so constrains all mortal men, because they behold many things come to pass on earth and in the sky, the cause of whose working they can by no means see, and think that a divine power brings them about. Therefore, when we have seen that nothing can be created out of nothing, then more rightly after that shall we discern that for which we search, both whence each thing can be created, and in what way all things come to be without the aid of gods. (Bailey)
This terror then, this darkness of the mind, must needs be scattered, not by the rays of the sun and the gleaming shafts of day, but by the outer view and the inner law of nature; whose first rule shall take its start for us from this, that nothing is ever begotten of nothing by divine will. (Bailey)
Or again, why do we see the roses in spring, and the corn in summer's heat, and the vines bursting out when autumn summons them, if it be not that when, in their own time, the fixed seeds of things have flowed together, then is disclosed each thing that comes to birth, while the season is at hand, and the lively earth in safety brings forth the fragile things into the coasts of light? But if they sprang from nothing, suddenly would they arise at uncertain intervals and in hostile times of year, since indeed there would be no first-beginnings which might be kept apart from creative union at an ill-starred season. (Bailey)
Nay more, there would be no need for lapse of time for the increase of things upon the meeting of the seed, if they could grow from nothing. For little children would grow suddenly to youths, and at once trees would come forth, leaping from the earth. But of this it is well seen that nothing comes to pass, since all things grow slowly, as is natural, from a fixed seed, and as they grow preserve their kind: so that you can know that each thing grows great, and is fostered out of its own substance. (Bailey)
There is this too, that without fixed rain-showers in the year the earth could not put forth its gladdening produce, nor again held apart from food could the nature of living things renew its kind or preserve its life; so that rather you may think that many bodies are common to many things, as we see letters are to words, than that without first-beginnings anything can come to being. (Bailey)
Once more, why could not nature produce men so large that on their feet they might wade through the waters of ocean or rend asunder mighty mountains with their hands, or live to overpass many generations of living men, if it be not because fixed substance has been appointed for the begetting of things, from which it is ordained what can arise? Therefore, we must confess that nothing can be brought to being out of nothing, inasmuch as it needs a seed for things, from which each may be produced and brought forth into the gentle breezes of the air. (Bailey)
Lastly, inasmuch as we see that tilled grounds are better than the untilled, and when worked by hands yield better produce, we must know that there are in the earth first-beginnings of things, which we call forth to birth by turning the teeming sods with the ploughshare and drilling the soil of the earth. But if there were none such, you would see all things without toil of ours of their own will come to be far better. (Bailey)
3. The Universe Is Made of Indivisible Particles - "Atoms" (meaning uncuttable)
Epicurean atomism stands in contrast to the "ideal forms" of Platonic philosophy or the "essentialism" of Aristotle. Epicurus holds that the reality of things to us arises from the movement of specific atoms through specific areas of void, while Plato and Aristotle contend that there is a "form" or an "essential" nature that lies behind or apart that makes a thing what it is. Classic examples include such things as color. Plato would hold that there is an "ideal form" of yellow, and Aristotle would hold that there is an "essence" of yellow, that makes a yellow thing yellow. In contrast, Epicurus would hold that the reality of yellow arises from the way our senses perceive particular combinations of atoms moving through space. The issue is whether yellow is something real. To Aristotle and Plato what we see as yellow is only an illusion, and that yellow exists only in ideal forms and essences which are perceptible only to reason, which makes reason the judge of reality. Epicurus holds that yellow is real because it is perceived by our senses, and this makes the faculties given to us by Nature the judge of reality.
The logical necessity of indivisible atoms follows from the principle established in A-2: if compounds dissolve, something must remain behind that does not dissolve, since otherwise all things would eventually perish into nothing and there would be no seeds for renewal. These remaining indivisible units are the atoms. They are not the smallest things we can see -- they are forever below the threshold of perception -- but their existence is deduced from the observable fact that things dissolve into something rather than into nothing.
Moreover, the totality of things is bodies and void. That bodies exist is universally witnessed by sensation itself, by reference to which it is necessary to judge by reason what is non-evident, as I have already said above. And if there were not that which we name void and room and intangible substance, bodies would not have anywhere to be or to move through in the way in which they are seen to move. Beyond these nothing can be conceived, either by comprehensive grasp or analogically to things grasped, as fully substantial entities, and not rather spoken of as the accidents or properties of such entities. (tr. Long & Sedley)
Moreover, among bodies, some are compounds, and others those from which compounds are made. And these latter are indivisible and unchangeable - if, that is, all things are not going to be destroyed into what is not, but are going to remain firmly in being during the dissolution of compounds - full in nature, and incapable of dissolution at any point or in any way. Therefore the principles of bodies must be the indivisible natures. (tr. Long & Sedley)
Moreover, among bodies, some are compounds, and others those from which compounds are made. And these latter are indivisible and unchangeable - if, that is, all things are not going to be destroyed into what is not, but are going to remain firmly in being during the dissolution of compounds - full in nature, and incapable of dissolution at any point or in any way. Therefore the principles of bodies must be the indivisible natures. (tr. Long & Sedley)
[Note: header locus corrected -- the real content below is Lucretius's "third nature" argument, Book I.420-451, not I.329-345; the same real passage in Bailey's own translation is quoted elsewhere in this file under the correct locus.]
Now I return to the sequence of my argument. All nature, then, as it exists in itself, is made up of just two components: there are bodies, and there is void in which those bodies are situated and through which they move this way and that. That body exists as an entity in its own right is declared by our sensation, universally shared. Unless confidence in this is firmly grounded in the first instance, there will be nothing by reference to which we could establish anything about what is hidden from our view, by proceeding through reasoning. Next, if there were no room and space, which we call void, bodies could not be situated anywhere, nor could they move this way and that at all, as I showed to you a short while before. Moreover, there is nothing you could posit which is separate from all body and distinct from void, to be discovered as a third nature: for whatever exists must be something in its own right; and if it admits of touch, however slight or great, as long as it exists, it will increase the tally of body by an increment large or small and be added to its sum; but if it is intangible and unable to prevent anything from moving freely through it in any direction, then it will certainly be that which we call empty void. Further, whatever exists in its own right, will either act, or must itself be acted on when other things act, or will be such that things are able to exist and happen in it. But nothing can act or be acted on without body, nor provide room except empty void. Therefore, other than void and bodies, no third nature could be left in the tally of things, either to fall under our senses at some time, or to be grasped by anyone through reasoning of the mind. (tr. Long & Sedley)
First, since we have found a vast difference between the twin natures of the two things - body, and the place in which everything happens - each must in itself be absolute and unmixed. For wherever there is the empty space which we call void, there no body exists, while wherever body is in occupation, there the emptiness of void is totally absent. Therefore the first bodies are solid and without void... These can neither be dissolved when struck by external blows, nor be dismantled through internal penetration, nor succumb to any other kind of attack, as I proved to you a little earlier. For we see that without void nothing can either be crushed, broken or cut in two, or admit moisture, permeating cold or penetrating fire. These cause the destruction of all things, and the more void each thing contains the more it succumbs to internal attack from them. So if the first bodies are solid and without void, as I have taught, they must necessarily be everlasting. Besides, if matter had not been everlasting, everything would before now have been totally annihilated, and all the things which we see would have been regenerated from nothing. But since I have taught earlier that nothing can be created from nothing and that what has been generated cannot be reduced to nothing, there must be principles with imperishable body, into which everything can be dissolved when its final hour comes, so as to ensure a supply of matter for the renewal of things. The principles, then, are solid and uncompounded, and in no other way could they have survived the ages from infinite time past to keep things renewed... Furthermore, since things have a limit placed on their growth and lifespan according to their species, and since what each can and cannot do is decreed through the laws of nature, and nothing changes but everything is so constant that all the varieties of bird display from generation to generation on their bodies the markings of their own species, they naturally must also have a body of unalterable matter. For if the principles of things could in any way succumb and be altered, it would now also be uncertain what can and what cannot arise, and how each thing has its power limited and its deep-set boundary stone, nor could such a long succession of generations in each species replicate the nature, habits, lifestyle and movements of their parents. (tr. Long & Sedley)
But lest you happen to mistrust my words on this, because the primary bodies of things escape the eye, let me tell you of others which, although you must admit they are in the class of bodies, yet are invisible. First, when it has gathered strength, the aroused force of the wind lashes the sea, capsizes huge ships and scatters the clouds; sometimes sweeping across the lands in rapid tornado, it strews the plains with massive trees, and batters the mountain-tops with forest-splintering blasts. That is when the wind howls with a fierce roar and storms with a threatening rumble. So winds, undoubtedly, are unseen bodies, which sweep the sea and lands and clouds in the sky, and assault and whirl them in sudden tornado; and their flow and the havoc they make are just the same as when water, which is of soft nature, carries a sudden flood. ... Next, aromas of various kinds we perceive, though we never see them coming to our nostrils; and we do not observe heat, nor can cold be caught by the eyes, nor are we used to seeing voices; yet all these things must consist of a bodily nature, since they can affect the senses. For nothing can touch or be touched without body. Furthermore, clothes hung up on a wave-beaten shore get moist, then spread out in the sun they get dry; yet we haven't seen how the moisture of water settled on them, nor again how it left under the influence of the heat. Therefore moisture is divided up into small parts which the eyes are quite incapable of seeing. Moreover, over many circuits of the sun a ring is worn thin on the finger by friction, dripping water hollows out stone, the curved iron ploughshare imperceptibly thins in the fields, and we see the stone pavement worn away by the feet of the crowd; then too the bronze statues by the gates show their right hands thinned by the frequent touching of people who pass by and greet them. We see, therefore, that all these things diminish as they are rubbed away; but nature has grudged our sight the power of discerning what particles leave at any particular time. (tr. Long & Sedley)
Epicurus says that the difference between void, place, and room is one of name. (tr. Long & Sedley)
Therefore one must grasp that, according to Epicurus, of 'intangible substance', as he calls it, one kind is named 'void', another 'place', and another 'room', the names varying according to the different ways of looking at it, since the same substance when empty of all body is called 'void,' when occupied by a body is named 'place', and when bodies roam through it becomes 'room'. But generically it is called 'intangible substance' in Epicurus' school, since it lacks resistant touch. (tr. Long & Sedley)
The atoms have no qualities at all except shape, weight and size and the properties that of necessity belong to shape. Every quality changes, but the atoms do not change at all. The shapes of atoms are incomprehensibly many but not infinite, for there are not atoms of every size. (Bailey, adapted)
- Page scan: Diogenes Laertius X.40-42 (tr. Bailey) -- same passage already clipped as part of the Letter to Herodotus (DL embeds the letter verbatim at this point in Book X)
- Online text: Diogenes Laertius 10.40-41 (Atomic Shapes Are Vastly Many But Not Infinite) -- Perseus Digital Library (Diogenes Laertius X, tr. Hicks, Loeb)
4. Atoms Cannot Be Infinitely Divided
Epicurus holds that atoms are not infinitely divisible, a position starkly in disagreement with earlier philosophers who held that there is no downward limit to division, as a result of which they reached absurd conclusions such as motion being impossible. As with all of the major components of atomism, this again arises from deductive reasoning, given that atoms cannot be perceived by human senses.
The doctrine of minimum parts (/elachista/) is Epicurus's specific and carefully developed answer to Aristotle's most powerful objection to atomism: that anything physically extended in space must be infinitely divisible in theory, because you can always conceive of dividing it in half. If this were true of atoms, the concept of a genuinely indivisible particle would be incoherent. Epicurus answered that atoms have a minimum spatial extent -- a smallest conceivable unit that cannot be divided even in thought -- and that this minimum is not itself a separate particle but rather the limit of what can be coherently said about spatial division. This was not a concession to Aristotle but a refutation: it showed that infinite theoretical divisibility does not follow from physical extension, and saved the atomic theory from what would otherwise have been a fatal objection. See also the discussion of this point in the jargon guide under "Elachista."
Furthermore, we must not consider that the finite body contains an infinite number of bits, nor bits with no [lower] limit to size. Therefore not only must we deny cutting into smaller and smaller parts to infinity, so that we do not make everything weak and be compelled by our conceptions of complex entities to grind away existing things and waste them away into non-existence, but also we must not consider that in finite bodies there is traversal to infinity, not even through smaller and smaller parts. For, first, it is impossible to conceive how [there could be traversal], once someone says that something contains an infinite n u m b e r of bits or bits with n o [lower] limit to size. Second, how could this magnitude still be finite? For obviously these infinitely many bits are themselves of some size, and however small they may be the magnitude consisting of them would also be infinite. And third, since the finite body has an extremity which is distinguishable, even if not imaginable as existing per se, one must inevitably think of what is in sequence to it as being of the same kind, and by thus proceeding forward in sequence it must be possible, to that extent, to reach infinity in thought. As for the minimum in sensation, we must grasp that it is neither of the same kind as that which admits of traversal, nor entirely unlike it; but while having a certain resemblance to traversable things it has no distinction of parts. Whenever because of the closeness of the resemblance we think we are going to make a distinction in it - one part on this side, the other on that -- it must be the same magnitude that confronts us. We view these minima in sequence, starting from the first, neither all in the same place nor touching parts with parts, but merely in their own peculiar way providing the measure of magnitudes - more for a larger magnitude, fewer for a smaller one. This analogy, we must consider, is followed also by the minimum in the atom: in its smallness, obviously, it differs from the one viewed through sensation, but it follows the same analogy. For even the claim that the atom has size is one which we made in accordance with the analogy of things before our eyes, merely projecting something small onto a large scale. We must also think of the minimum uncompounded limits as providing out of themselves in the first instance the measure of lengths for both greater and smaller magnitudes, using our reason to view that which is invisible. For the resemblance which they bear to changeable things is sufficient to establish this much; but a process of composition out of minima with their own movement is an impossibility, (tr. Long & Sedley)
- Page scan: Epicurus, Letter to Herodotus 56-57 (tr. Bailey), same page also carries sec. 55
- Page scan: Epicurus, Letter to Herodotus 58 (tr. Bailey), same page also carries secs. 59-60
- Online text: Epicurus, Letter to Herodotus 56-58 (The Theory of Minimum Parts) -- Perseus Digital Library (Diogenes Laertius X, tr. Hicks, Loeb)
Then again, seeing that there is always a final extremity of that body which is below the threshold of our senses, it is presumably partless and of a minimal nature, and never was or could be separated by itself, since its very existence is as a part of something else: it is one part, the first, and is followed by similar parts in sequence, one after another, filling out the nature of the body in dense formation. Since these cannot exist by themselves, they must stick together inextricably. Therefore the primary particles are solid and uncompounded, being tightly packed conglomerations of minimal parts, not composed by assembling these but rather gaining their strength through being everlastingly uncompounded. Nature is still preventing anything from being prised away or subtracted from them, but preserves them as seeds for things. Besides, unless there is going to be a minimum, the smallest bodies will consist of infinitely many parts, since half of a half will always have a half and there will be nothing to halt the division. In that case, what is the difference between the universe and the smallest thing? None. For however utterly infinite the whole universe is, the smallest things will nevertheless consist equally of infinitely many parts. Since true reasoning protests against this and denies that the mind can believe it, you must give in and concede the existence of those things which possess no parts and are of a minimal nature. Since these exist, you must admit that those things too [the atoms] are solid and everlasting. Finally, if nature the creator of things were in the habit of forcing everything to be resolved into its minimal parts, she would by now be unable to renew anything out of them, because things which are not swollen by any parts cannot possess the properties required in generative matter - the variety of connections, weights, blows, conjunctions and motions which are responsible for everything that happens. (tr. Long & Sedley)
[Proponents of the four-element theory are mistaken] secondly in that they place absolutely no limit on the cutting up of bodies and no end to their fragmentation, and no minimum in things, even though we see that final extremity of each thing which to our senses seems to be a minimum -- from which you can guess that the extremity which invisible things possess is the smallest thing in them. (tr. Long & Sedley)
Furthermore one should not suppose that every size exists among atoms, lest the evidence refute us, but one must think that there are some differences in size. For if this obtains, then that which occurs in our feelings and sensations can better be accounted for. But the existence of every size is not useful to the explanation of the differences in qualities, and at the same time it would be necessary for some atoms to come within our purview and be visible. But this is not seen to occur, nor is it possible to conceive in what way an atom could become visible. (tr. Long & Sedley)
- Page scan: Epicurus, Letter to Herodotus 55 (tr. Bailey), same page also carries secs. 56-57
- Online text: Epicurus, Letter to Herodotus 55 (corrected from a stated locus of "68-71" -- this is the atomic-size passage, not the passage actually found at secs. 68-71) -- Perseus Digital Library (Diogenes Laertius X, tr. Hicks, Loeb)
(1) Now it is time for me to explain that there is nothing visible which consists of atoms of just one kind, nothing which is not formed from seeds of mixed birth; and the more powers and capacities anything possesses in itself, the more it declares that there are in it the greatest number of kinds of atoms and the variety of their shapes. (2) First of all, the earth contains in herself the atoms from which springs, forever rolling cool waters, renew the boundless sea; she has atoms from which fires arise. For in many regions the earth's surface burns and blazes, while raging Etna erupts in flames from her deepest furnaces. Next she has the seed from which she can raise shining crops and joyful trees for the human race, from which she can supply to the mountain-wandering tribe of wild beasts streams and leaves and gladsome pastures. (3) Wherefore she alone has been named Great Mother of the gods, mother of beasts, and parent of our body. ... (4) Wherefore I repeat that there must be many atoms common to many things in common combinations, as we see letters common to words; and yet you must admit that different things are constituted of different letters. Not that only a few letters run through them in common, or that any two things are made up of all the same letters, but that not all in general are alike to all. (5) So in other things likewise: although many atoms are common to many things, yet they can none the less constitute altogether dissimilar wholes; so that the human race, crops, and joyful trees are rightly said to be created from different atoms. (tr. Long & Sedley)
5. The Only Eternal Properties of Atoms Are Shape, Weight, and Size
Epicurus held that atoms have only three inherent properties: (1) shape, (2) weight, and (3) size. As a result Epicurus concludes that atoms have no other properties, and qualities which we attribute to bodies (which are formed by combinations of atoms) are /events/ which arise from interaction of those bodies with our senses. Atoms have "weight" which gives them motion, and as Lucretius explains, atoms can swerve in their motion at no fixed time and no fixed place. Atoms have no intelligence inherent in them, nothing exists or is perceived by us as "real" other than combinations of atoms and void and the properties and qualities of the bodies that arise from them.
This three-property limitation has a consequence of enormous philosophical importance: because atoms possess /only/ shape, weight, and size, every other quality we observe in the world -- color, taste, temperature, sound, sensation, life, and thought -- must be a property of the /compound/, not of any individual atom. No individual atom is colored, warm, sweet, or alive. All of these are emergent properties of the compounds atoms form. This is the physical foundation of the doctrine of emergence developed in A-8, and it is what makes Epicurean physics fully consistent with the reality of pleasure, pain, friendship, and all the other things that matter to us: they are real, not illusions, but they are real at the level of compounds and organisms, not at the level of atoms.
In addition, these bodies which are atomic and full, from which compounds are formed and into which they are dissolved, have unimaginably many differences of shape. For it is not possible for as many varieties as there are to arise from the same shapes if these are of an imaginable number. For each species of shape, also, the number of atoms of the same kind is absolutely infinite; but in the number of their differences they are not absolutely infinite, just unimaginably many, if one is not going to expand them to absolute infinity in their sizes too. (tr. Long & Sedley)
Moreover, there are in the atoms no quality at all except shape, weight and size, and whatever is a necessary concomitant of shape. For every quality changes; but the atoms do not change in any way, since it is necessary in the case of the dissolutions of compounds for something solid and indestructible to remain behind, which will not bring about changes into what is not, or out of what is not, but changes in arrangements, and in some cases additions and subtractions of atoms. Hence what is indestructible must not have the nature of quality, but only of shape and size and weight. (4) For these necessarily remain, whereas qualities do not remain but change with the general aggregate. (tr. Long & Sedley)
Moreover, one must not postulate that every shape belongs to the atoms; otherwise each one will come into view. One must rather suppose that the shapes are dissimilar, but not every dissimilarity, and the totality of dissimilar shapes not infinite but merely incomprehensible. And the atoms have no quality at all except shape, size and weight. (4) But colour varies according to the disposition of the atoms. (tr. Long & Sedley)
Moreover, the atoms themselves must be considered to exhibit no quality of things evident, beyond shape, weight, size, and the necessary concomitants of shape. For all quality changes. But the atoms do not change at all, since something solid and indissoluble must survive the dissolution of the compounds to ensure that the changes are not into, or out of, the non-existent, but result from transpositions within many things, and in other cases from additions and subtractions of certain things. Hence those things which do not admit of [internal] transposition must be indestructible, and must lack the nature of that which changes. And their own peculiar masses and shapes must survive, since this is actually necessary. After all, also in familiar objects which have their shape altered by shaving, it can be ascertained that in the matter which undergoes change, as it is left, shape remains whereas the qualities do not remain but vanish from the entire body. So these properties which are left are sufficient to bring about the differences of the compounds, given the necessity for some things to be left and not be destroyed into the non-existent. (tr. Long & Sedley)
W e must not adopt, either, the view that every size is to be found among the atoms, lest it be contested by things evident. On the other hand, we must suppose that there are some variations of size, for this addition will yield better explanations of the events reported by our feelings and senses. But the existence of every size is not useful with respect to the differences of qualities. Indeed, we ourselves ought to have experienced visible atoms, and that is not seen to happen, nor is it possible to conceive how a visible atom might occur. (tr. Long & Sedley)
We examine these beginning from the first and not in the same spot, nor touching parts to parts, but in their own nature as things that measure sizes, more of them measuring a greater thing and fewer of them a lesser. (Furley)
[Above: tr. Furley. Below: the same passage in Bailey's translation, same page also carries secs. 59-60.]
And since I have taught this much, I will hasten to link on a truth which holds to it and wins belief from it, that the first-beginnings of things, which are formed with a shape like to one another, are in number infinite. For since the difference of forms is limited, it must needs be that those which are alike are unlimited, or else that the sum of matter is created limited, which I have proved not to be. (Bailey)
(1) One must think that in limited bodies there is something which cannot even be seen. (2) It is clear that this thing is without parts and is the minimum in nature; and it neither arose as self-constituted on its own, nor could it ever arise as such, but it was and is always in being as a part of something else, being the first and unique and in sequence next primary part of a thing, until other such parts in order constitute by their collective union the full nature of the body. (3) Just as in the case of the soul it is impossible to conceive of the aggregate nature apart from the whole compound, so in these cases too it is impossible; evidently, therefore, these parts necessarily pre-exist. (4) Now, it is necessary that these minimal parts in the atoms should also be thought of as boundaries providing length's measure in themselves both for the smaller and the greater; for the analogous study of what is visible through reason leads to that which is non-evident. (5) For the partlessness that there is in them is sufficient to produce this result by analogy with compound bodies, though such precise identification is impossible. (6) It is necessary also to suppose that limited bodies contain a sum total of such parts, whether they be smaller or greater ones. (7) And it is clear that this minimum is similar in a certain analogous way to the things which undergo change; but that it differs also by its special mode of compounding. (8) For indeed by analogy to this we have declared the atom's nature to be continuous, although we can isolate and define the individual measures by means of distinctive qualities. (9) But it is necessary also to postulate that in continuous things length is not built up out of contact, nor is it necessary to suppose that, in any magnitude whatsoever, there is infinity in the direction of decrease. (tr. Long & Sedley)
But in the case of atoms one must not suppose that they have every magnitude, lest the evidence refute us, but one must think that there are some differences in size. For if this obtains, then that which occurs in our feelings and sensations can better be accounted for. But the existence of every size is not useful to the explanation of the differences in qualities, and at the same time it would be necessary for some atoms to come within our purview and be visible. But this is not seen to occur, nor is it possible to conceive in what way an atom could become visible. (tr. Long & Sedley)
- Page scan: Epicurus, Letter to Herodotus 55 (tr. Bailey), same page also carries secs. 56-57
- Online text: Epicurus, Letter to Herodotus 55 (corrected from a stated locus of "61-2" -- this is the atomic-size passage, not the equal-velocity passage actually found at secs. 61-62) -- Perseus Digital Library (Diogenes Laertius X, tr. Hicks, Loeb)
Moreover, there are in the atoms no quality at all except shape, weight and size, and whatever is a necessary concomitant of shape. For every quality changes; but the atoms do not change in any way, since it is necessary in the case of the dissolutions of compounds for something solid and indestructible to remain behind, which will not bring about changes into what is not, or out of what is not, but changes in arrangements, and in some cases additions and subtractions of atoms. Hence what is indestructible must not have the nature of quality, but only of shape and size and weight. For these necessarily remain, whereas qualities do not remain but change with the general aggregate. (tr. Long & Sedley)
(1) Now come: since I have shown that there exist completely solid bodies of matter flying around for ever, unconquered through eternity, let us unroll whether or not there is any limit to their total number; likewise let us elucidate whether the void which has been discovered, or room or space, in which individual things take place, is altogether finite or stretches away boundless and immeasurably deep. (2) Well then, the universe as a whole is bounded in no direction; for if it had a limit it would have to have an extremity. But it is seen that nothing can have an extremity unless there is something beyond to bound it, so that something is seen to exist up to which the nature of our sense can follow it no further. Now since we must admit that there is nothing beyond the totality, it does not have an extremity, it therefore lacks end and measure. (3) And it makes no difference in which region of it you take up your position: whatever spot anyone occupies, he leaves the universe just as infinite as before in all directions. (4) Moreover, supposing for the moment that the whole of space were bounded, if someone ran right to its furthest shores and hurled a flying javelin, do you choose to think that that javelin, hurled with great force, would go where it was sent and fly far, or do you think that something could block its path and stop it? (5) For you must adopt and admit one of the two; yet both cut off your escape and compel you to grant that the universe extends without limit. For whether there is something to block it and prevent it from arriving where it was sent and lodging in its target, or whether it passes out, it did not start from the end. By this method I shall follow you up, and wherever you place the furthest shores I shall ask, 'What then happens to the javelin?' (6) The result will be that the boundary cannot stand anywhere, and that the chance of flight will always prolong the chance of escape. (tr. Long & Sedley)
Moreover, if anyone thinks that the atoms can stop, and by stopping generate new motions in things, he is straying far away from true reasoning. For since the atoms are wandering through the void, they must all be borne along either by their own weight or by a chance blow from another atom. For when, as often happens in their movements, they have met and clashed together, the result is a sudden leap apart in opposite directions; which is not surprising, since they are extremely hard with solid weight, and there is nothing behind to obstruct them. And the better to perceive that all particles of matter are in a state of turbulence, recall that there is no bottom in the universe, and that the atoms have no place in which to come to rest, since space is without end or limit and extends immeasurably in every direction, as I have shown by sure proof and as from the facts has been truly established. Since this is certain, beyond doubt no rest is granted to the atoms moving through the profound void, but driven on rather by varied incessant motion, some when they have collided leap back leaving great spaces between, while others are thrust only a short way from the impact. And those which, having been more closely massed in denser union, recoil through minute intervals, entangled by their own interlocking shapes, these constitute the strong roots of stone and the savage body of iron and other things of that kind. Of the remainder which wander through the great void, a few leap far apart and recoil far back with great spaces between; these provide us with rare air and brilliant sunlight. And many more besides wander through the great void, having been rejected from combinations of things, unable anywhere to be admitted and to link their movements in harmony. (tr. Long & Sedley)
(1) Herein lies another fact which I want you to grasp. (2) When bodies are being borne downwards through the void by their own weight, at absolutely unpredictable times and places they deflect slightly from their vertical course, just enough that you can call it a change of direction. (3) If they did not swerve, they would all fall downwards like drops of rain through the profound void, and no collision would occur, nor would any blow be produced among the atoms. In that case nature would never have created anything. (4) But if anyone happens to believe that heavier atoms, through being carried more swiftly in a vertical line through the void, can fall from above upon lighter ones, thereby producing the blows which can give rise to the generative motions, he is straying far from the path of truth. (5) For the reason why things falling through water and thin air must accelerate their fall in proportion to their weight is simply that the body of water and the subtle nature of air cannot retard each thing equally, but more quickly give way, overpowered by heavier bodies. (6) But on the other hand the empty void cannot offer resistance to anything at any time or in any place, but must, as its nature demands, go on giving way. (7) Therefore all things must move at equal velocity through the unresisting void, though they are of unequal weight. (8) Thus heavier things will never be able to fall from above upon lighter ones or of themselves produce impacts capable of generating the varied motions by which nature carries on her work. (9) Wherefore again and again the atoms must swerve slightly - but only by the minimum amount, lest we appear to be inventing oblique motions and the facts prove us wrong. (10) For we see this to be manifest and evident, that heavy things, in so far as they are heavy, cannot travel obliquely of their own accord, when they fall from above, as far as you can observe. (11) But that nothing at all swerves from a straight course, who is there who can perceive? (tr. Long & Sedley)
It is very easy, with the mind's reasoning, for us to work out why the fire of lightning flows with much more penetration than the fire which we produce from torches here on earth. All you need say is that the lightning's fire up in the sky is finer and consists of smaller shapes, and hence passes through passages through which this fire which we produce from logs and torches cannot pass. Besides, light passes through horn, while rain water is rejected by it. Why, unless the particles of light are smaller than those which make up water's nourishing draught? And however instantaneously we see wine flow through a sieve, olive oil, by contrast, is sluggish and takes its time. This is naturally either because it consists of larger elements; or because they are more hooked together entangled, with the consequence that individual primary particles cannot be so immediately separated and flow individually through each thing's passages. A further point is that the liquids of honey and milk, when taken by mouth, are pleasant to the tongue's sensation, while, by contrast, foul wormwood and pungent centaury twist up the mouth with their repellent flavor. Thus you can easily recognize that those things which can have a pleasant effect on the senses consist of smooth round particles, while by contrast all those which seem bitter and harsh are joined and interwoven with more hooked particles, and for that reason tend to make violent inroads into our senses, and to wrench our body when they enter it. (tr. Long & Sedley)
Having explained this, I shall go on to attach to it a point which depends on it for its proof; that the primary elements of things have a finite range of different shapes. Should this not be so, it will again necessarily follow that some seeds have infinite bodily extension. For within one and the same narrow compass of a given body there cannot be much variety of shapes. Say, for example, that atoms consist of three minimal parts or a few more. Well obviously, when you have taken all these parts of one body, positioned them cop and bottom, swapped left with right, and in short tried every permutation to see what shape of the whole body each arrangement yields, should you want to vary the shapes further you will have to add more parts. And the next stage will be that, should you want to vary the shapes even further, the arrangement will require more parts in just the same way. Thus a consequence of adding new shapes is bodily increase. So there is no way in which you can suppose the seeds to have infinitely many differences of shape, lest you force some to be immensely huge, which I have already explained above to be unacceptable. You would find, too, that exotic garments, glowing Meliboean purple dyed with the colour of Thessalian shells, and the golden generations of peacocks bathed in their smiling charm, would by now lie neglected, outshone by some new color appearing in things. The fragrance of myrrh would lie in disrepute, as would the taste of honey. And the melodies of swans and the intricate string music of Apollo would likewise have been outshone and silenced. For one thing would constantly be arising to eclipse the others. And in the same way all things would be able to change in the reverse direction for the worse, just I have said they could change for the better. For one thing would also in the reverse direction be more revolting than all the rest for nose, ears, eyes, and the mouth's taste. Since this is not so, but the totality of things is held in check at either end of the scale by the assignment of a fixed limit, you must admit that matter also has a finite number of different shapes. Again, from fire right down to the icy frosts of winter is a finite passage, and in the reverse direction it is measured in the same way. For all heat, cold, and lukewarm temperatures, making up the whole range in succession, lie in between. Therefore they are generated with a finite range of differences, since they are marked off by two points, one at either end of the scale -- hemmed in by fire at one end and stiff frost at the other. Having explained this, I shall go on to attach to it a point which depends on it for its proof: that the primary elements of things, within each group of the same shape as each other, must be called infinitely many. For since there is a finite variety of shapes, it is necessary that those of a single shape be infinitely many. Otherwise the totality of matter must be finite, which I proved not to be the case when I showed in my poem that particles of matter from the infinite permanently maintain the totality of things with a continuous succession of impacts from all sides. (tr. Long & Sedley)
Come now, mark what I say, the fruit of my pleasant labors - that you should not suppose those white objects which you see before your eyes as white to consist of white primary particles, or those which are black to be the product of black seeds, or that objects dyed any other- color exhibit it because their particles of matter are imbued with the same color. For particles of matter have absolutely no color, whether like or unlike that of the objects. You are quite wrong if you think that the mind cannot be focused on such particles. For given that those who are blind from birth and have never seen the sun's light nevertheless from their first day know bodies by touch without any association of color, you can be sure that our mind too can form a preconception of bodies without any coating of color. In fact, we ourselves sense as colorless everything that we touch in blind darkness. Besides, if the primary particles are colorless, and possess a variety of shapes from which they generate every kind of thing and thus make colors vary -- since it makes a great difference with what things and in what sort of position the individual seeds are combined and what motions they impart to each other and receive from each other - it at once becomes very easy to explain why things which a little earlier were black in color can suddenly take on the whiteness of marble, as the sea, when its surface has been churned up by great winds, is turned into waves whose whiteness is like that of gleaming marble. All you need say is that what we regularly see as black comes to appear gleaming white as soon as its matter is mixed up, as soon as the ordering of its primary particles is changed, as soon as some particles are added and some subtracted. But if the sea's surface consisted of blue seeds, there is no way in which they could turn white. For things that are blue could never change to the color of marble, no matter how you were to jumble them up... Moreover, the tinier the pieces into which any object is shredded, the more you can see the gradual disappearance and blotting out of its color. This happens, for example, when purple cloth is pulled apart into little pieces: when it has been dismantled thread by thread, the purple and the scarlet color, by far the brightest there is, is completely wiped out. So you can tell from this that fragments breathe away all their color before they are reduced to the seeds of things. (tr. Long & Sedley)
Hence when Epicurus asserts that we conceive body by means of a combination of size and shape and resistance and weight, he is forcing us to form a conception of existent body out of non-existents; for if no size exists apart from that which is endowed with size, nor shape apart from what is shaped, nor resistance apart from what resists, how is it possible from things non-existent to form a conception of an existent body? (Bury)
For if the corporeal is, as Epicurus says, a combination of magnitude, shape and solidity massed together, -- or, as the Mathematicians assert, that which is three-dimensional, that is to say compounded of length, breadth and depth, -- or that which has three dimensions plus solidity (another definition of Epicurus: in order to distinguish it thus from void), -- or, as others say, a solid mass, -- be this as it may, inasmuch as the corporeal is conceived as a combination of a number of separate factors, and the combining of many is not the operation of a simple and irrational sense but of a rational intellect, the corporeal will not be one of the sensibles. (Bury)
6. The Atoms Have Always Been In Motion And Always Will Be
Epicurus held that atomic motion is a natural property of atoms and in no way supernatural. There are three types of atomic motion: downward movement through the void by reason of weight; rebound from collision with other atoms; and the spontaneous swerve (/parenklisis/ in Greek, called /clinamen/ by Lucretius) -- a small, uncaused deviation from a straight path that occurs at no fixed time or place.
The swerve is Epicurus's most important and deliberate departure from Democritus, who held that all atomic motion is strictly necessary and determined by prior causes. If Democritus were right, everything in the universe -- including every human decision -- would be the inevitable output of prior atomic arrangements, leaving no room for genuine freedom of choice. The swerve breaks this chain of necessity: it introduces genuine indeterminacy at the physical level, and it is the physical foundation for the reality of human free will. Without it, the entire Epicurean ethical project -- which assumes that we can deliberate, choose wisely, and be held responsible for our choices -- would be incoherent.
The swerve also solves a physical problem: atoms falling straight down through void in parallel paths would never collide, and without collision no worlds could ever form. The spontaneous deviation allows collisions, and from collisions the variety of compound things we observe arises.
Moreover, the atoms move continuously for all time, some recoiling far apart from one another, others maintaining the vibration when they happen to be caught in an interlocking or covered by interlocking atoms. For the nature of void brings this about by separating each atom by itself, since it is unable to provide support; and their own solidity makes them, on rebounding, vibrate to whatever distance the interlocking permits them to return from the collision. And there is no beginning to this, because of the eternity of the atoms and the void. (tr. Long & Sedley)
Moreover, the lack of obstruction from colliding bodies makes motion through the void achieve any imaginable distance in an unimaginable time. For it is collision and non-collision that take on the resemblance of slow and fast. Nor, on the other hand, does the moving body itself reach a plurality of places simultaneously in the periods of time seen by reason. That is unthinkable. And when in perceptible time this body arrives in company with others from some point or other in the infinite, the distance which it covers will not be one from any place from which we may imagine its travel. For that will resemble [cases involving] collision - even if we do admit such a degree of speed of motion as a result of non-collision. This too is a useful principle to grasp. (tr. Long & Sedley)
Moreover the atoms must be of equal velocity whenever they travel through the void and nothing collides with them. For neither will the heavy ones move faster than the small light ones, provided nothing runs into them; nor will the small ones move faster than the large ones, through having all their trajectories commensurate with them, at any rate when the large ones are suffering no collision either. Nor will either their upwards motion or sideways motion caused by knocks [be quicker], or those downwards because of their individual weights. For however far along either kind of trajectory it gets, for that distance it will move as fast as thought, until it is in collision, either through some external cause or through its own weight in relation to the force of the impacting body. Now it will also be said in the case of compounds that one atom is faster than another, where they are in fact of equal velocity, because the atoms in the complexes move in a single direction even in the shortest continuous time, although it is not single in the periods of time seen by reason; but they frequently collide, until the continuity of their motion presents itself to the senses. (tr. Long & Sedley)
If you think that the primary particles can stand still, and can thus initiate motions of things from scratch, you are wandering far from true reasoning. For since they wander through void, they must necessarily all be borne along either by their own weight or, if it should so happen, by the impact of another. For as a result of their frequent high-speed collisions they recoil suddenly in opposite directions - not surprisingly, given that they are entirely hard with their solid weights and unobstructed by anything from behind. And to see more clearly that all particles of matter are being tossed about, remember that in the totality of the universe there is no bottom and that the primary bodies have nowhere to stand still, since room has no limit or boundary and I have shown at length and proved with conclusive argument that it stretches measureless in all directions. Since that is established, naturally the primary bodies are granted no rest throughout the depths of void. But rather they are driven in continuous and varied motion, and some after being squeezed together rebound over great intervals, while others are tossed about over short spaces from the impact. And whichever ones are in a denser aggregation and rebound over small intervals from that impact, held back by the interweaving of their own shapes, these form the strong roots of stone, the brute bulk of iron, and the like. Those others which go on wandering through the great void, few and far between, and recoil and rebound a long way over great intervals, these supply the thin air for us and the sun's brilliant light. In addition many wander through the great void, which have been rejected by compounds and have also failed to gain admittance anywhere and harmonize their motions. Of this fact, as I have recounted it, there is a pictorial representation regularly present and taking place before our eyes. Take a look where the sun's rays weave their way in and pour their light through a darkened room. You will see many tiny bodies intermingling in many ways throughout the empty space right there in the light of the rays, and as if in everlasting combat battling and fighting ceaselessly in their squadrons, driven by frequent meetings and separations. So you can conjecture from this what it is like for the primary particles of things to be for ever tossed around in the great void. To some extent something small can give a model of great matters, and the traces of their preconception. (tr. Long & Sedley)
Here now, Memmius, is a brief account from which you may know the speed which the particles of matter possess. First, when dawn spreads new light over the earth, and the various birds flying about the pathless woods through the soft air fill the place with their flowing voices, we see it plainly revealed to all how suddenly the risen sun at such a rime regularly swamps all things and clothes them with its own light. And yet the heat and calm light which the sun emits does not travel through empty void, and so is compelled to go more slowly as it beats its way through the waves, so to speak, of the air; nor do the particles of heat travel individually, but in interlinked aggregations. Hence they are simultaneously retarded by each other and obstructed from outside, and are thus compelled to go more slowly. But when the solid and uncompounded primary particles travel through empty void, and are both unimpeded from outside and, being such a unity of its own parts, borne hurtling onward in their one initial direction of movement, they must naturally be of supreme swiftness, and travel much faster than the sun's light, and traverse many times the extent of space in the same time as the sunlight takes to cross the sky. (tr. Long & Sedley)
On this topic, another thing I want you to know is this. When bodies are being borne by their own weight straight down through the void, at quite uncertain times and places they veer a little from their course, just enough to be called a change of motion. If they did not have this tendency to swerve, everything would be falling downward like raindrops through the depths of the void, and collisions and impacts among the primary bodies would not have arisen, with the result that nature would never have created anything. But if anyone should suppose it possible that heavier bodies, by virtue of their faster travel in a straight line through the void, should land from above on lighter ones and in that way produce impacts capable of leading to creative motions, he is departing far from true reasoning. For whatever things fall through water and thin air must necessarily fall at a speed proportionate to their weight, since the body of water and the rarefied substance of air cannot impede everything equally, but succumb and yield faster to heavier things. But the emptiness of void, by contrast, can nowhere and at no rime stand up to anything, but must constantly, as its nature demands, give way. Through the passive void, consequently, ail things must travel at equal speed, regardless of differences in weight. Hence it will never be possible for the heavier ones to land from above on the lighter ones and by themselves produce impacts resulting in the variety of motions through which nature does her work. Thus it follows once again that the bodies must veer off a little - no more than one minimum, lest we item to be inventing oblique motions and be refuted by the facts. For we see as plain and obvious that weights when hurtling downwards have no intrinsic power to travel obliquely. But who in the world can see that they do not swerve from their straight trajectory at all? (tr. Long & Sedley)
For unless every magnitude were divisible, it would not be possible for the slower always to move less distance than the faster in equal time; for that which is atomic, and that which is partless, are traversed by the faster in the same time as they are by the slower. For if the slower takes a longer time, in the equal time it is going to traverse a distance smaller than the; partless. That is why Epicurus' school holds that all things move at the same speed through the partless places, lest their atoms be divided and thus no longer atoms. (tr. Long & Sedley)
That this obstacle which he [Aristotle] has formulated is itself not entirely beyond belief is shown by the fact that despite his having formulated it and produced his solution, the Epicureans, who came along later, said that this is precisely how motion does occur. For they say that motion, magnitude and time have partless constituents, and that over the whole magnitude composed of partless constituents the moving object moves, but at each of the partless magnitudes contained in it it does not move but has moved; for if it were laid down that the object moving over the whole magnitude moves over these too, they would turn out to be divisible. (tr. Long & Sedley)
7. In Addition To Atoms, Empty Space - The Void - Must Also Exist
Proof of the existence of void comes through deductive reasoning based on the evidence of the senses, not directly through the senses alone, as the atoms and void are not directly observable by the senses.
And if there were not that which we name void and room and intangible substance, bodies would not have anywhere to be or to move through in the way in which they are seen to move. (tr. Long & Sedley)
So there exists intangible place, void and emptiness. Otherwise there would be no way in which things could move. For that which is the function of body, to hinder and block, would be there to affect everything at all times; so that nothing would be able to move forward, since nothing would start the process of giving way. But as it is, we see before our eyes many things moving in many different ways, through seas, lands and the lofty skies. If void did not exist, these things would not just be deprived of their restless motion: they would never have come into being at all, since matter would everywhere be jammed solid and at rest. Besides, however solid things may be thought to be, you can see that their bodies are porous from the following facts. In rocks and caves the liquid moisture of water seeps through and everything weeps with an abundance of drops. Food spreads itself throughout animals' bodies. Trees grow and in season pour forth their fruits because their food spreads throughout them from the tips of their roots up, through their trunks and through all their branches. Voices permeate walls and fly across between closed houses. Brittle cold penetrates to the bones. There is no way in which you could see this happen without the existence of voids for the individual bodies to pass through. Next, why do we see some things exceed others in weight without being larger than them? For if there is as much body in a ball of wool as there is in lead, they ought to weigh the same, since the function of body is to push everything down, while the nature of void on the contrary remains weightless. It naturally follows that what is equally large but seems lighter reveals that it contains more void, while by contrast what is heavier announces itself as containing more body and much less void. Naturally, then, the thing we call void, which we are seeking with keen reasoning, is mingled with things. On this topic, I am compelled to forestall a fiction of some people, in case it leads you away from the truth. These people say that the waters give way to the pressure of scaly fish and open liquid paths because the fish leave places behind them into which the waters which give way then flow; and that this is also how other things can move in relation to each other and change place, even though everything is full. You can see t the theory in its entirety has been accepted on false reasoning. For which way, after all, will the scaly fish be able to move forward unless the waters have provided space for them? And which way, moreover, will the waters be able to retreat, when the fish will be unable to move? Therefore either we must deny motion to all bodies, or we must say that void is mingled with things and provides each thing with the beginning of motion. Finally, if two broad bodies, which have come together, quickly spring apart, it is of course necessary that air come to occupy all the void created between them. Now however fast the currents with which the air converges from all sides, it will still be impossible for the entire space to be filled at one and the same time. For it must occupy each successive place before the whole space is occupied. (tr. Long & Sedley)
[Above: Long & Sedley excerpt. Below: the same passage in Bailey's translation, tr. Bailey, De Rerum Natura I.327-389.]
[Note: header corrected from "1.483-502" to the real locus, verified against the rendered page -- this is the wind/invisible-bodies passage.]
Now since I have shown that things cannot be created from nothing, and likewise that once created they cannot be called back to nothing, let me now add, lest you start to mistrust my words because the primary elements of things escape the eyes, a list of other bodies, which you too are bound to admit to be in the class of things and yet not to be visible. In the first place, aroused by force, the wind batters the sea, sinks huge ships and scatters clouds. Sometimes in a rapid whirlwind it sweeps across the plains, strewing them with large trees, and hammers the mountain peaks with forest-splitting gusts. So savagely does the wind howl in its shrillness and storm with menacing roar. Undoubtedly, therefore, there are unseen bodies of wind which sweep the sea, the lands, and finally the clouds in the sky, and assault and carry them off in a sudden tornado. They flow and cause destruction in just the same way as the soft nature of water, when all at once an overwhelming river of water rushes down from high mountains after massive rains, hurling together broken branches from forests and entire trees; nor can strong bridges withstand the sudden onrush of advancing water. The river, swollen with heavy rains, dashes against the piers with mighty force; with loud noise it makes havoc, and rolls huge boulders under its waves and demolishes whatever opposes its current. So then must the blasts of wind too be carried along. When like a mighty river they have hurled themselves in any direction, they push things before them and sweep them away in repeated assaults, and sometimes seize them up in swirling eddy and bear them away in a rapidly whirling tornado. (4) Therefore I repeat, there are unseen bodies of wind, since in their effects and behavior they are found to rival the great rivers, which are of manifest body. (tr. Long & Sedley)
[Note: header corrected from "2.80-141" to the real locus, verified against the rendered page -- this is the swerve-of-the-atoms passage, same underlying passage already clipped elsewhere in this file for the AtomicMotion topic.]
In this connection, there is one fact which I wish you to grasp; when atoms are being carried downwards through the void by their own weight, at absolutely unpredictable times and places they deflect slightly from their straight course, to a degree that could be described as no more than a shift of movement. If they were not apt to swerve, all would fall downwards through the profound void like drops of rain, no collision would occur, and no blow would be brought about amongst the atoms. In that case, nature would never have created anything. But if anyone happens to think that heavier atoms, in virtue of being carried more quickly in a straight line through the void, can fall from above on the lighter ones and thereby bring about the blows capable of giving rise to creative motions, he is straying far from true reasoning. For the reason why things which fall through water or rare air must speed up their fall in proportion to their weights is simply that the body of water and the rare nature of air cannot slow down each thing equally, but give way more quickly when overcome by heavier bodies. On the other hand, the empty void cannot on any side, at any time, support anything, but must, as its nature demands, go on giving way. Therefore all things must be borne on through the calm void, moving at equal rate with unequal weights. Hence heavier atoms will not ever be able to fall on lighter ones from above, or by themselves generate the blows which vary the motions through which nature carries out her work. Therefore, again and again, the atoms must swerve slightly - but no more than the minimum; otherwise we will seem to be inventing oblique movements, and the truth of the matter will refute us. For we see this manifestly and evidently, that weights, in so far as they are weights, cannot move obliquely when they fall from above, as far as you can observe. But who is there who can perceive that they in no way deflect from a precisely straight course? (tr. Long & Sedley)
[Compare Against the Logicians II.329: "Epicurus, for instance, opines that he has put forward a very strong argument for the existence of void, namely this -- 'If motion exists, void exists; but in fact motion exists; therefore void exists.'"]
And lack of contrary testimony is the congruity of the supposed and opined non-evident object with the apparent -- as when Epicurus says that void exists, which is a thing non-evident, and this is supported by an obvious fact, namely motion; for if void does not exist, neither ought motion to exist, the moving body having no place into which to pass over, owing to the fact that all things are full and close-packed; so that, since motion exists, the apparent does not give testimony that contradicts the opined non-evident fact. (Bury)
8. Atoms Come Together Through Space To Form Bodies With Qualities That Are Transient
Combinations of atoms moving through void result in bodies which become perceptible to our senses. These bodies have properties and qualities, some of which cannot be separated from the body without destroying it, while others are temporary, and our observation of them varies depending upon circumstances.
This is one of the most philosophically important and practically consequential insights in all of Epicurean physics. The atoms themselves, as established in A-5, have only three properties: shape, weight, and size. Individual atoms are colorless, tasteless, odorless, soundless, and without sensation. Yet the world we observe is saturated with color, taste, smell, sound, and sensation -- and Epicurus holds that these observable properties are fully and genuinely real. They are not illusions, not mere appearances masking a "truer" atomic reality beneath them, and not convenient fictions that sophisticated philosophers should see through. The color of the sea, the sweetness of honey, the pain of a wound, the pleasure of a warm fire -- all of these are real properties of real compounds, arising from the organization of atoms even though no individual atom possesses any of them.
This is what modern philosophy calls "emergence": properties that are absent at the level of the basic constituents but genuinely present at the level of the compounds those constituents form. The whole is greater than the sum of its parts -- not in a vague or mystical sense, but in the precise sense that the compound genuinely possesses properties that its individual components do not.
The classical scholar David Sedley, in his paper "Epicurus' Refutation of Determinism," identifies this as one of Epicurus's most important departures from Democritus. Sedley calls it "anti-reductionism": the Epicurean insistence that the observable world is just as real as the atomic world, and that the properties of compound things cannot be dismissed as mere appearances. For Epicurus, there are two genuinely real levels: the level of atoms and void, and the level of compound things observable by the senses. Neither level cancels the other.
This has profound practical consequences. If pleasure were merely an appearance at the compound level, reducible to atomic motion at the "true" level, the entire Epicurean claim that pleasure is the natural guide of life would be undermined. If the fear of death were merely an appearance, it could not be therapeutically addressed by genuine understanding. If friendship were merely an atomic alias, it could not be the greatest good wisdom can secure. Emergence -- the genuine reality of compound properties -- is the physical foundation on which all of Epicurean ethics rests.
Lucretius illustrates the same insight through an analogy that is one of the most elegant in ancient philosophy: atoms are like the letters of the alphabet. Individual letters have a limited set of properties. But combined into words, they produce meanings -- properties entirely absent from any individual letter -- and combined in different arrangements, the same letters produce entirely different words with entirely different meanings. So atoms, combined in different arrangements, produce compounds with properties -- color, life, sensation -- that no individual atom possesses, and different arrangements produce compounds with entirely different properties. The same elements, differently organized, give rise to fire and water, to oak trees and human beings, to honey and wormwood.
Moreover, among bodies, some are compounds, and others those from which compounds are made. (tr. Long & Sedley)
Now as for the shapes, colours, sizes, weights, and other things predicated of a body as permanent attributes - belonging either to all bodies or to those which are visible, and knowable in themselves through sensation - we must not hold that they are per se substances: that is inconceivable. Nor, at all, that they are non-existent. Nor that they are some distinct incorporeal things accruing to the body. Nor that they are parts of it; b t that the whole body cannot have its own permanent nature consisting entirely of the sum total of them, in an amalgamation like that when a larger aggregate is composed directly of particles, either primary ones or magnitudes smaller than such-and-such a whole, but it is only in the way I am describing that it has its own permanent nature consisting of the sum total of them. And these things have their own individual ways of being focused on and distinguished, yet with the whole complex accompanying them and at no point separated from them, but with the body receiving its predication according to the complex conception. Now there often also accidentally befall bodies, and impermanently accompany them, things which will neither exist at the invisible level nor be incorporeal. Therefore by using the name in accordance with its general meaning we make it clear that 'accidents' have neither the nature of the whole which we grasp collectively through its complex (of attributes] and call 'body', nor that of the permanent concomitants without which body cannot be thought of. They can get their individual names through certain ways of being focused on, in concomitance with the complex, but just whenever they are each seen to become attributes of it, accidents being impermanent concomitants. And we should not banish this self-evident thing from the existent, just because it does not have the nature of the whole of which it becomes an attribute -- 'body', as we also call it -- nor that of the permanent concomitants. Nor should we think of them as per se entities; that is inconceivable too, for either these or the permanent attributes. But we should think of all the accidents of bodies as just what they seem to be, and not as permanent concomitants or as having the status of a per se nature either. They are viewed in just the way that sensation itself individualizes them. Now another thing that it is important to appreciate forcefully is this. We should not inquire into time in the same way as other things, which we inquire into in an object by referring them to familiar preconceptions. But the self-evident thing in virtue of which we articulate the words 'long time' and 'short time', conferring a uniform cycle on it, must itself be grasped by analogy. And we should neither adopt alternative terminology for it as being better -- we should use that which is current -- nor predicate anything else of it as having the same essence as this peculiar thing -- for this too is done by some -- but we must merely work out empirically what we associate this peculiarity with and tend to measure it against. After all, it requires no additional proof but merely empirical reasoning, to see that with days, nights, and fractions thereof, and likewise with the presence and absence of feelings, and with motions and rests, we associate a certain peculiar accident, and that it is, conversely, as belonging to these things that we conceive that entity itself, in virtue of which we use the word 'time'. (tr. Long & Sedley)
- Page scan: Epicurus, Letter to Herodotus 71-73 (tr. Bailey) -- secs. 71-73 shown (the covers the accidents/permanent-attributes and time doctrine); secs. 68-70 precede on an earlier page, not separately clipped here
- Online text: Epicurus, Letter to Herodotus 68-73 -- Perseus Digital Library (Diogenes Laertius X, tr. Hicks, Loeb)
Therefore no third substance beside void and bodies can be left in the sum of things, neither one that could fall under our senses at any time nor one that anyone could grasp by the mind's reasoning. For all things which are spoken of you will find to be either fixed attributes of these two or accidents of them. A fixed attribute is that which can at no point be separated and remove d without fatal destruction resulting -- as weight is to stones, heat to fire, liquidity to water, tangibility to all bodies, and intangibility to void, By contrast slavery, poverty, wealth, freedom, war, peace, and all the other things whose arrival and departure a thing's nature survives intact, these it is our practice to call, quite properly, accidents. Time, likewise, does not exist per se: it is from things themselves that our perception arises of what has happened in the past, what is present, and further what is to follow it next. It should not be conceded that an y on e perceives time per se in separation from things' motion and quiet rest. Moreove , when people say that the rape of Helen and the defeat in war of the Trojan tribes are facts, we must be careful that they do not force us into an admission that these things exist per se on the ground that the generations of men of whom they were accidents have by now been taken away by the irrevocable passage of rime. For all past facts can be called accidents, either of the world or of actual places. And besides, if there had been no matter for things, and no place and space, in which all events occur, never would that flame kindled deep in Paris' Phrygian heart and fanned with love through Helen's beauty have ignited the shining battles of savage war, nor would that wooden horse by giving birth to its Grecian offspring at dead of night have set tire to the citadel undetected by the Trojans. Thus you can see that it is fundamental to all historical facts not to exist per se like body, and not to be or to be spoken of in the way in which void exists, but rather in such a way that you can properly call them accidents of body and of the place in which all events occur. (tr. Long & Sedley)
Now what in themselves are called elements, you can see to be all either primary, if of a single nature, like heat and moisture and earth and breath, or not primary, like bones and blood and sinew, when each borrows its nature from the joining together of several different seeds. For of things which are named after atoms and are constituted out of atoms, some take on the names of those atoms from which they are mostly made; but some take on the names and nature of something other, in virtue of whichever element is predominant. ... Next, accidents of things you could by no means regard as a nature independent in its own right, nor can they be said to exist in the manner of void: rather, it is correct to call them accidents of body, and of the place in which all things occur. But time does not exist in its own right. Rather, from the facts themselves there follows a sense of what has been completed in past time, of what is presently to hand, and further of what is going to follow afterwards; and we must accept that no one has a sense of time in its own right, as distinct from the movement or the quiet rest of things. (tr. Long & Sedley)
Epicurus, as Demetrius of Laconia interprets him, says that time is an accident of accidents, one which accompanies days, nights, hours, the presence and absence of feelings , motions and rests. For all of these are accidents belonging to things as their attributes, and since time accompanies them all it would be reasonable to call it an accident of accidents. For - to start at a slightly earlier point so as to make the account intelligible -- it is a universal principle that of things that exist some are per se while others are viewed as belonging to per se things. What exist per se are things like the substances, namely body and void, while what are viewed as belonging to per se things are what they call 'attributes'. Of these attributes some are inseparable from the things of which they are attributes, others are of a kind to be separated from them. Inseparable from the things of which they are attributes are, for example, resistance from body and non-resistance from void. For body is inconceivable without resistance, and so is void without non-resistance: these are permanent attributes of each -- resisting of the one, yielding of the other. Not inseparable from the things of which they are attributes are, for example, motion and rest. For compound bodies are neither always in ceaseless motion nor always at rest, but sometimes have the attribute of motion, sometimes that of rest (although the atom in itself is in everlasting motion, since it must approach either void or body and if it should approach void it moves through it because of its non- resistance, while if it should approach body it ricochets and moves away from it because of its resistance). Hence the things which time accompanies are accidents -- I mean day, night, hour, presence and absence of feelings, motions and rests. For day and night are accidents of the surrounding air: day becomes its attribute because of its illumination from the sun, while night supervenes because of its deprivation of illumination from the sun. And the hour, being a part either of day or of night, is also an accident of the air just as day and night are. And co extensive with every day, night and hour is time. That is why a day or a night is called long or short: we pass through the time which is an attribute of it. As for presence and absence of feelings, these are either pains or pleasures, and hence they are not substances, but accidents of those who feel pleasant or painful - and not timeless accidents. In addition, motion and likewise rest are also, as we have already established, accidents of bodies and not timeless: for the speed and slowness of motion, and likewise the greater and smaller amount of rest, we measure with time. (tr. Long & Sedley)
Or do you think, on the basis of the foregoing argument, that someone would not suffer the troubles which I mention but rather would make it convincing that fair, foul and all other matters of belief are wholly believed in, just because unlike gold and similar things they are not the same everywhere? After all, it must stare everybody in the face that bigger and smaller are also not perceived the same everywhere and in relation to all magnitudes ... So too with heavier and lighter. And the same applies also to other powers, without exception. For neither are the same things healthy for every body, nor nourishing or fatal, nor the opposites of these, but the very same things are healthy and nourishing for some yet have the opposite effect on others. Therefore either they must say that these too are false -- things whose effects are plain for everyone to see - or else they must refuse to brazen it out and to battle against what is evident, and not abolish fair and foul as falsely believed in either, just because unlike stone and gold they are not the same for everybody... Relative predicates do not have the same status as things said not relatively but in accordance with something's own nature. Nor does the one kind truly exist but not the other. So to expect them to have the same attributes, or the one kind to exist but not the other, is naive. And there is no difference between starting from these and eliminating those and starting from those and eliminating these: it would be similarly naive to think that since the bigger and heavier and sweeter are bigger than one thing but smaller than another, and heavier, and likewise with the other attributes, and since nothing has the same one of these attributes per sea it has in relation to something else, in the same way stone, gold and the like ought also, if they truly existed, to be gold in relation to one person while having the opposite nature in relation to another; and to say that, since that is not the case, these things are falsely believed in and do not really exist. (tr. Long & Sedley)
[Note: header corrected from "2.730-764" to the real locus, verified against the rendered page.]
(1) Now it is time for me to explain that there is nothing visible which consists of atoms of just one kind, nothing which is not formed from seeds of mixed birth; and the more powers and capacities anything possesses in itself, the more it declares that there are in it the greatest number of kinds of atoms and the variety of their shapes. (2) ...Wherefore I repeat that there must be many atoms common to many things in common combinations, as we see letters common to words; and yet you must admit that different things are constituted of different letters. Not that only a few letters run through them in common, or that any two things are made up of all the same letters, but that not all in general are alike to all. (3) So in other things likewise: although many atoms are common to many things, yet they can none the less constitute altogether dissimilar wholes; so that the human race, crops, and joyful trees are rightly said to be created from different atoms. (tr. Long & Sedley)
Moreover, do not think that only the colors of things are unable to accrue to the atoms; shapes too are entirely separated from them, and similarly weight, and cold, and heat, and all other rapidly alternating qualities. All these are properties of things, not the atoms themselves. When we see a thing change in color from moment to moment, yet the substance of the thing does not thereby perish -- this tells us that color emerges from atomic arrangements and not from the atoms themselves. (Bailey, adapted)
[Note: this is a loose paraphrase, not a direct quotation; the underlying passage is Bailey's translation of the "atoms have no colour" argument, De Rerum Natura II.720-781.]
Some of the physicists, however, -- and amongst them Epicurus -- have declared that the motion of change is a particular form of transitional motion; for the composite object which changes in quality changes owing to the local and transitional motion of the rationally perceived bodies which compose it. Thus, in order that a thing may become bitter from sweet, or black from white, the molecules which compose it must be arranged in a new order and take up different positions; and this could not be brought about otherwise than by the transitional motion of the molecules. And again, -- in order that a thing may become soft from hard or hard from soft, the parts whereof it is composed must move in place; for it is made soft by their expansion, but made hard by their coalescence and condensation. (Bury)
9. Images, Sensations, and Memory
Human consciousness (mind) operates totally naturally and has no supernatural component. As with anything else, the senses are emergent aspects of atoms moving through void, and the movement of atoms is required for the senses to operate. Each of the five senses operates through the movement of atoms. In addition to the five senses of seeing, hearing, touching, tasting, and smelling, Epicurus held that the mind is able to perceive the patterns of "images" that result when other bodies give off particles that move in our direction. While we refer today to images as things which are perceived by the eyes, Epicurus also referred to images as being received directly by the mind as a result of perceiving the patterns which particles retain as they move through space.
The Epicurean account of atomic films (/eidōla/, called /simulacra/ by Lucretius) is not merely a curiosity of ancient physics but the physical mechanism by which the reliability of the senses, asserted in B-2, is grounded. Sensation is not a subjective projection onto the world; it is a genuine physical contact between the sense organ and material arriving from the external object. The film arriving from the object carries the shape and arrangement of that object, and the sense organ receives that physical imprint. This is why sensation is always accurate as sensation: it is a real physical effect of a real physical cause. Error enters only when the mind adds an opinion about what the sensation means -- not in the sensation itself.
Moreover, there are delineations which represent the shapes of solid bodies and which in their fineness of texture are far different from things evident. For it is not impossible that such emanations should arise in the space around us, or appropriate conditions for the production of their concavity and fineness of texture, or effluences preserving the same sequential arrangement and the same pattern of motion as they had in the solid bodies. These delineations we call images. Next, that the images are of unsurpassed fineness is uncontested by anything evident. Hence they also have unsurpassed speed, having every passage commensurate with themselves, in addition to the fact that infinitely many of them suffer no collision or few collisions, whereas many, indeed infinitely many, atoms suffer immediate collision. Also that the creation of the images happens as fast as thought. For there is a continuous flow from the surface of bodies - not revealed by diminution in their size, thanks to reciprocal replenishment - which preserves for a long time the positioning and arrangement which the atoms had in the solid body, even if it is also sometimes distorted; and formations of them in the space around us, swift because they do not need to be filled out in depth; and other ways too in which things of this kind are produced. For none of this is contested by our sensations, if one is considering how to bring back self-evident impressions from external objects to us in such a way as to bring back co-affections too. And we must indeed suppose that it is on the impingement of something from outside that we see and think of shapes. For external objects would not imprint their own nature, of both color and shape, by means of the air between us and them, or by means of rays or of any effluences passing from us to them, as effectively as they can through certain delineations penetrating us from objects, sharing their color and shape, of a size to fit into our vision or thought, and traveling at high speed, with the result that their unity and continuity then results in the impression, and preserves their co-affection all the way from the object because of their uniform bombardment from it, resulting from the vibration of the atoms deep in the solid body. And whatever impression we get by focusing our thought or senses, whether of shape or of properties, that is the shape of the solid body, produced through the image's concentrated succession or after-effect. But falsehood and error are always located in the opinion which we add. For the portrait-like resemblance of the impressions which we gain either in sleep or through certain other focusings of thought or of the other discriminatory faculties, to the things we call existent and true, would not exist if the things with which we come into contact were not themselves something. And error would not exist if we did not also get a certain other process within ourselves, one which, although causally connected, possesses differentiation. It is through this that, if it is unattested or contested, falsehood arises, and if attested or uncontested, truth. This doctrine too, then, is a very necessary one to grasp, so that the criteria based on self-evident impressions should not be done away with, and so that falsehood should not be treated as equally established and confound everything. Hearing too results from a sort of wind traveling from the object which speaks, rings, bangs, or produces an auditory sensation in whatever way it may be. This current is dispersed into similarly-constituted particles. These at the same time preserve certain co-affection in relation to each other, and a distinctive unity which extends right to the source, and which usually causes the sensory recognition appropriate to that source, or, failing that. just reveals what is external to us. For without a certain co-affection brought back from the source to us such sensory recognition could not occur. We should not, then, hold that the air is shaped by the projected voice, or likewise by the other things classed with voice. For the air will be much less adequate if this is an effect imposed on it by the voice. Rather we should hold that the impact which occurs inside us when we emit our voice immediately squeezes out certain particles constitutive of a wind current in a way which produces the auditory feeling in us. W e must suppose that smell too, just like hearing, would never cause any feeling if there were not certain particles traveling away from the object and with the right dimensions to stimulate this sense, some kinds being disharmonious and unwelcome, others harmonious and welcome. (tr. Long & Sedley)
- Page scan: Epicurus, Letter to Herodotus 46-53 (tr. Bailey) -- section 46 shown; the cited range continues through sec. 53 across subsequent pages (secs. 50-52 separately clipped elsewhere in this file)
- Online text: Epicurus, Letter to Herodotus 46 -- 53 -- Perseus Digital Library (Diogenes Laertius X, tr. Hicks, Loeb)
(1) I say then that likenesses of things and thin shapes are emitted from things off their surfaces; these can be called films or even bark, because each image bears an appearance and form resembling the body from whatever object it flows and wanders forth. ... (2) For certainly we perceive even in plain sight that many things throw off bodies, some dispersed loosely like smoke from burning logs and heat from fires, others more closely woven and dense, like the slender tissue which cicadas sometimes doff in summer, and the caul which calves cast off from their surface at birth, and likewise the garment which the slippery snake sheds among thorns - for often we see brambles enriched with these wind-blown spoils of snakes. (3) Since such things occur, thin images too must likewise be emitted from things off their outermost surface. ... (4) These simulacra are borne along with the highest speed and mobility; first because a minute cause deep inside is enough to push and start them, since they are so fine and thin; next, because being of such loose-woven texture they easily pass through anything and as it were filter through the intervening air. (tr. Long & Sedley)
Nor in this do we admit that the eyes are in any way deceived. For their function is to see where light and shade are; but whether it is the same light, and whether the shadow that was here is the same one passing over there -- or whether rather it happens as I said a little while ago -- this the mind's reason must determine. The eyes cannot know the nature of things; so do not accuse the eyes of a fault that belongs to the mind. A ship in which we sail is carried along, though it seems to stand still; another, which stays at her moorings, is believed to be passing by. Hills and plains seem to fly backward as we urge our ship forward and sail past them with oars flying. When we gaze long at the stars, they all seem to whirl, quite still though they are. And if we stand long and then suddenly turn round, the buildings seem to wheel and the columns to rotate. So great and various are the illusions -- and yet in all these cases we admit that the appearances are produced by real atoms moving in the real world. The fault lies in the opinion, the judgment that we add, not in the act of perception itself. (Bailey, adapted)
- Page scan: Lucretius, De Rerum Natura IV.406-465 (tr. Bailey), catalogue of sensory illusions (page 1 of 2) -- header locus corrected from stated 379-417
- Page scan: Lucretius, De Rerum Natura IV.406-465 (tr. Bailey), catalogue of sensory illusions (page 2 of 2)
- Online text: Lucretius 4.379 (tr. Leonard) -- Perseus Digital Library
Besides, since a given shape handled in the dark is recognized to be the same on e as it is seen to be in clear daylight, touch and sight must be moved by a similar cause. Thus if in the dark we probe and are moved by what is square, what will the square thing be which in the light can impinge on vision, if not its image? Hence it can be seen that the cause of vision lies in the images, and that without these nothing can be seen. (tr. Long & Sedley)
One thing in this matter which should not be thought puzzling is why, although the images which strike the eyes cannot be seen individually, the objects themselves are perceived. For also when wind beats on us little by little, and when bitter cold creeps on us, we do not normally feel every separate particle of that wind and that cold, but rather the combination of them, and we see on those occasions an effect in our body just as if some object were bearing us and imparting to us a sensation of its bodily mass from outside. Furthermore, when we knock a stone with our finger we are touching its external outermost color, but what we are sensing with our touch is not that but rather the actual hardness deep down within the stone. (tr. Long & Sedley)
(1) Now I will explain what it is that rouses the mind, and whence come the things which enter the understanding - and that in few words. (2) First I say this, that many simulacra of things wander about in many ways in all directions, fine films which easily unite with one another when they meet in the air, like spider's web and gold-leaf. (3) For indeed these films are far finer in texture than those which occupy the eyes and provoke vision, since these penetrate through the body's pores and wake the mind's fine nature within and provoke sensation there. (4) And so we see Centaurs and the limbs of Scyllas and the dog-faces of Cerberus and images of those who are dead and whose bones are held in earth's embrace - since simulacra of every kind are being borne everywhere, some produced spontaneously in the air itself, some departing from various things, and others formed and made up from combinations of these. (5) For certainly the image of a Centaur does not come from a living creature, since no such nature of living creature ever existed, but when images of a man and a horse have chanced to come together, they easily stick at once on meeting, as we said before, because of their fine nature and delicate fabric. Others of this type are created in the same way. Because, as I showed earlier, their extreme lightness makes their travel so mobile, it is easy for any one fine image to arouse our mind with a single impact. For the mind is itself delicate and extraordinarily mobile. That this happens as I say it does you can easily tell as follows. In so far as what we see with the mind is similar to what we see with the eyes, it must come about in a similar way. Well, since I have proved that it is by means of whatever images stimulate my eyes that I see, say, a lion, you can now tell that the mind is moved in a similar way through images of lions and equally through the others it sees, no less than the eyes except in that what it discerns is more delicate. And when sleep has relaxed the limbs the mind stays awake in just the same way, except that these same images which stimulate our minds while we are awake do so to such an extent that we seem to see beyond all doubt someone who has departed this life and is dead and buried. The reason why nature compels this to happen is that all the bodily senses are suppressed and at rest throughout the limbs and cannot convict falsehood with the true facts. Moreover, the memory lies in slumber and does not protest that the man whom the mind thinks that it sees alive is long dead. This matter raises many questions, and there is much that we must clarify if we want to expound the facts clearly. The first question is why each person's mind immediately thinks of the very thing that he has formed a desire to think of. Do the images observe our will, so that as soon as we form the wish the images impinge on us, whether our desire be to think of sea, land or sky? Are assemblies, parades, parties and battles all created and supplied by nature on demand, and in spite of the fact that everything which the minds of other people in the same place are thinking of is quite different? A further question is, what about our seeing in our dreams the images rhythmically going forward and moving their supple limbs, when they fluently swing their supple arms in alternation and before our very eyes replicate the gesture with matching foot movements? No doubt the images are steeped in technique, and have taken lessons in wandering to enable them to have fun at nighttime! Or will this be nearer the truth? Because within a single period of time detectable by our senses - the time it takes to utter a single sound - there lie hidden many periods of time whose existence is discovered by reason, it follows that everywhere at every time every image is ready on the spot: so great is the speed and availability of things. And because they are delicate the mind can only see sharply those of them which it strains to see. Hence the remainder all perish, beyond those tor which the mind has prepared itself. The mind further prepares itself by hoping to see the sequel to each thing, with the result that this comes about. Don' t you see how the eyes too, when they begin to see things which are delicate, strain and prepare themselves, and that there is no other way of seeing sharply? As a matter of fact, even with things plain to see you can discover that the result of failing to pay attention is that it becomes like something separated from you by the whole of time and far away. Why then is it surprising if the mind loses everything else beyond the matters to which it is devoting itself? As for the other point, it is not surprising that the images move and rhythmically swing their arms and other limbs. The image seems to do this in dreams because when the first image perishes and a second then arises in a different stance it looks as if the first had changed its pose. You can take it that this happens fast, so great is the speed and availability of things. And so great is the availability of particles within a single period of time detectable by the senses that it is capable of keeping up the supply. We then on the basis of slender evidence add weighty opinions and plunge ourselves into the trickery of deception. Occasionally, too, an image of the same kind is not supplied, but what was previously a woman seems to have turned into a man in our arms, or one face or age is followed by another. The fact that this does not surprise us is the doing of sleep and oblivion. (tr. Long & Sedley)
What is viewed by the eyesight is inherited by the soul, and after the impingements of the original images passages are opened up in us in such a way that, even when the objects which we originally saw are no longer present, our mind admits likenesses of the original objects. (tr. Long & Sedley)
- Page scan: Diogenes of Oinoanda, Fr. 9 (tr. Smith)
[Above: Long & Sedley excerpt. Below: the same passage in Bailey's translation.]
Also, all notions arise from the senses by means of confrontation, analogy, similarity and combination, with some contribution from reasoning too. (tr. Long & Sedley)
Dreams have no divine character nor any prophetic force, but they originate from the influx of images. (Bailey)