1. "All Sensations Are True"
The Epicurean claim that "all sensations are true" is one of the most misunderstood positions in the philosophy, and it is important to state it precisely. Epicurus was fully aware that illusions occur and that our senses can present us with information that leads to mistaken judgments. Lucretius devotes extensive sections of On The Nature of Things to explaining the mechanics of how optical illusions and other misleading perceptions arise. The claim is not that everything we perceive is accurately interpreted by the mind. It is that the sensations themselves -- as raw reports of what is affecting our sense organs -- are genuine data and not fabrications. Error lies in the mind's judgment about what the senses are reporting, not in the sensory data itself.
The practical and philosophical importance of this position is that the senses -- along with anticipations and feelings -- are the only faculties nature has given us for evaluating reality. The senses must therefore be treated as the foundation of all knowledge rather than dismissed as unreliable or deceptive. To declare the senses systematically untrustworthy, as Plato and the Academic skeptics effectively did, is to destroy the only ladder by which we can climb to any knowledge at all. The Epicurean philosopher therefore does not distrust sensory experience but learns to interpret it correctly -- applying judgment carefully and holding off assent to conclusions that go beyond what the evidence supports.
It is instructive to contrast this position with that of the Stoics, with whom Epicurus was in direct and conscious opposition. The Stoics held that impressions can be either true or false, and that only a special class of impressions -- the "kataleptic" impression -- carries its own certification of accuracy. This required elaborate training in dialectic to identify which impressions were kataleptic. For Epicurus, this entire apparatus is unnecessary and misdirected: sensations, as non-rational physical contacts between sense organ and external object, cannot be false in themselves. They simply register what they receive. Only when the reasoning mind adds an opinion to the sensory report does the possibility of error arise -- and it is there, not in the sensation, that philosophy must do its therapeutic work. The Epicurean position is at once more naturalistic (sensation is a simple physical process, not a rational judgment) and more universally accessible (no special training is needed to have reliable sensations; every person of normal faculties has them from birth).
We must consider both the real purpose and all the evidence of direct perception, to which we always refer the conclusions of opinion; otherwise, all will be full of doubt and confusion. (Bailey)
If you fight against all sensations, you will not have a standard against which to judge even those of them you say are mistaken. (tr. Long & Sedley)
(1) Moreover, one must suppose that it is when something from external objects enters into us that we not only see but also think of their shapes. (2) For external objects would not imprint in us the nature of their colour and shape through the air which is between them and us, nor through rays or any kind of flow going from us to them, as well as by means of certain outlines coming from the objects to us, in colour and shape of sizes commensurate with our vision and our thought, moving swiftly; then, by the presentation of a single continuous outline, they produce an impression and the attendant sensation in virtue of their constant repetition from the object. (tr. Long & Sedley)
And every presentation and sensation that we get, whether of shape or of properties, will be the actual shape of the solid object, produced by the repeated impact or residue of the image. (tr. Long & Sedley)
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. (tr. Long & Sedley)
[Above: Long & Sedley excerpt. Below: the same argument (the exhaustive division of nature into body and void) in Bailey's translation -- the real locus is I.420-451, not I.329-45.]
Nor in this [shadow illusions] do we admit that the eyes are in any way deceived. For their function is to see where light and shade are. But whether or not it is the same light, and whether the shadow that was here is the same one as is passing over there, or whether rather it happens in the way we said a moment ago, this falls to the mind's reason to discern. The eyes cannot discover the nature of things. So do not trump up this charge against the eyes for a fault which belongs to the mind. (tr. Long & Sedley)
When we see from far off the square towers of a city, the reason why they often seem round is that any corner is seen as blunted from a distance, or rather is not seen at all, its impact fading away and failing to complete the passage to our eyes, because during the images' travel through a large expanse of air the corner is forced to become blunt by the air's repeated buffetings. Thus, when all the corners simultaneously escape our sensation, it becomes as if the stone structures are being smoothed on a lathe. They are not, however, like things genuinely round seen close-to, but seem to resemble them a little in a shadowy sort of way. (tr. Long & Sedley)
(1) Now for what reason that image is seen beyond the mirror, I will tell. Certainly it appears thrust far back inside. Just so we see things which are in fact outside a doorway through doors when the door affords an unobstructed view through it out to the open and displays many outside things. (2) For that vision too is brought about by two separate airs. First the air on this side of the door-posts is seen, then follow the door-leaves themselves to right and left, next the light outside filters through the eyes and a second air, and then the things which are in fact seen out there. (3) So when the mirror's image first projects itself, while it is coming to our eyes it pushes and drives before it all the air which is between it and our eyes, and makes us able to perceive all this before the mirror. (4) But when we have also perceived the mirror itself, immediately the image that travels from us reaches the mirror and being reflected returns to our eyes and drives another air onwards before itself and makes us see it before itself and for that reason appears to stand so far away from the mirror. (5) Wherefore again and again there is no reason at all why we should wonder, both about those things which send back a view from the surface of mirrors, and about those beyond double doors, since in both cases the result is brought about by two separate airs. (tr. Long & Sedley)
- Page scan: Lucretius, De Rerum Natura IV.259-289 (tr. Bailey) -- header locus corrected from stated 478-521; the manuscript lacuna in Bk IV means the mirror passage is actually at this locus
- Page scan: Lucretius, De Rerum Natura IV.290-314 (tr. Bailey), continued
- Online text: Lucretius 4.259 (tr. Leonard) -- Perseus Digital Library
All sensation, he [Epicurus] says, is irrational and does not accommodate memory. For neither is it moved by itself, nor when moved by something else is it able to add or subtract anything. Nor does there exist that which can refute sensations: neither can like sense refute like, because of their equal validity; nor unlike unlike, since they are not discriminatory of the same things; nor can reason, since all reason depends on the senses; nor can one individual sensation refute another, since they all command our attention. And also the fact of sensory recognitions confirms the truth of sensations. And our seeing and hearing are facts, just as having a pain is. Hence sign-inferences about the non-evident should be made from things evident. (tr. Long & Sedley)
We hold that vision perceives visibles and touch tangibles, that the one is of color, the other of body, and that the one never interferes in the other's sphere of discrimination. For if it were the case that vision perceived the size and shape of body, it would much sooner perceive body itself.... <To see shape is only to perceive the color's> outline, and often not even that. If, then, visible shape is nothing but the external positioning of the colors, and visible size nothing but the positioning of the majority of the colors in relation to what lies outside, it is perhaps possible for that whose function is to register colors themselves to perceive the external positioning of the colors.... So it is by recourse to analogy that shape and size are spheres of discrimination common to these senses: as the shape and size of the color are to the color, so the shape and size of the body are to the body: and as the color is to visual perception, so the body is to perception by touch.... Apart from the very broad and general respects discussed above we do not hold that there is, in the direct way, a common sphere of discrimination. In the indirect way, the one which exhibits such generality that it could easily be called analogy, we could say that shape is their common sphere of discrimination... Let us then add a reminder of what peculiar characteristic each of the senses exhibits, apart from the sensory recognition of their objects of discrimination. Well, the most peculiar characteristic of vision as compared to the other senses, apart from the discrimination of colors and the things related to them, is the perception of shape at a distance, together with sensory recognition of the interval between itself and them... Touch, as far as its peculiar function is concerned, has [as its most peculiar characteristic] that of registering no quality at all. As far as concerns its common function of registering the qualitative states of the flesh - a concomitant property of the other senses too -- it has as its most peculiar characteristic that of registering different kinds of qualities: for as well as discriminating hard and soft, it perceives both hot and cold, both within itself and adjacent to itself... Although vision does not discriminate solidity, some people deceive themselves through thinking that it does. For they suppose that when we see rocks vision through its simple application conveys their solidity. (tr. Long & Sedley)
[Summarizing Epicurus] Some people are deceived by the difference among impressions seeming to reach us from the same sense-object, for example a visible object, such that the object appears to be of a different color or shape, or altered in some other way. For they have supposed that, when impressions differ and conflict in this way, one of them must be true and the opposing one false. This is simple-minded, and characteristic of those who are blind to the real nature of things. For it is not the whole solid body that is seen -- to take the example of visible things - but the color of the solid body. And of color, some is right on the solid body, as in the case of things seen from close up or from a moderate distance, but some is outside the solid body and is objectively located in the space adjacent to it, as in the case of things seen from a great distance. This color is altered in the intervening space, and takes on a peculiar shape. But the impression which it imparts corresponds to what is its own true objective state. Thus just as what we actually hear is not the sound inside the beaten gong, or inside the mouth of the man shouting, but the sound which is reaching our sense, and just as no one says that the man who hears a faint sound from a distance is mis-hearing just because on approaching he registers it as louder, so too I would not say that the vision is deceived just because from a great distance it sees the tower as small and round but from near-to as larger and square. Rather I would say that it is telling the truth. Because when the sense-object appears to it small and of that shape it really is small and of that shape, the edges of the images getting eroded as a result of their travel through the air. And when it appears big and of another shape instead, it likewise is big and of another shape instead. But the two are already different from each other: for it is left for distorted opinion to suppose that the object of impression seen from near and the one seen from far off are one and the same. The peculiar function of sensation is to apprehend only that which is present to it and moves it, such as color, not to make the distinction that the object here is a different one from the object there. Hence for this reason all impressions are true. Opinions, on the other hand, are not all true but admit of some difference. Some of them are true, some false, since they are judgments which we make on the basis of our impressions, and we judge some things correctly, but some incorrectly, either by adding and appending something to our impressions or by subtracting something from them, and in general falsifying irrational sensation. (tr. Long & Sedley)
[Above: Long & Sedley excerpt. Below: the same passage in full surrounding context, tr. Bury, Loeb , Against the Logicians I.205-212.]
Epicurus used to say that all sensibles are true, and that every impression is the product of something existent and like the thing which moves the sense; and that those who say that some impressions are true but others false are wrong, because they cannot distinguish opinion from self-evidence. At any rate, in the case of Orestes, when he seemed to see the Furies, his sensation, being moved by the images, was true, in that the images objectively existed; but his mind, in thinking that the Furies were solid bodies, held a false opinion. (tr. Long & Sedley)
[Above: Long & Sedley excerpt (this same page also carries the following Plutarch entry). Below: the same Orestes passage in full surrounding context, tr. Bury, Loeb , Against the Logicians II.62-66.]
As for the famous 'matching-sizes' and 'consonances' of the passages belonging to the sense organs, and 'multiple-mixtures' of the seeds which they [the Epicureans] say are distributed through all flavors, smells and colors and move different sensations of quality in different people, do these not drive things together right into the 'no more this than that' class, on their view? For to reassure those who think that sensation is deceived because they see its users affected in opposite ways by the same things, they teach the doctrine that since all things are jumbled and mixed up together, and some things are of a nature to fit into some things, others into others, it is not the same quality that is being brought into contact; and apprehended, nor does the object move everyone in the same way with all its parts; rather, all individuals encounter only the things of a size to match their own sense, and therefore are wrong to dispute about whether the thing is good or bad or white or non-white in the belief that by confuting each other's sensations they are confirming their own. One should not resist a single sensation, for they all make contact with something, each of them taking from the multiple mixture, as from a well, whatever is fitting and appropriate to itself. And when we are making contact with parts we should make no assertions about the whole. Nor should we think that everyone is affected in the same way, since some are affected by one quality and power, some by another. (tr. Long & Sedley)
[Above: tr. Goodwin (1874), Against Colotes the Epicurean, full surrounding context. Below: the same passage as excerpted by Long & Sedley.]
- Page scan: Plutarch, Against Colotes 1109C-E (tr. Goodwin, 1874)
- Page scan: Plutarch, Against Colotes 1109C-E (tr. Long & Sedley)
- Online text: Plutarch, Against Colotes (tr. Goodwin, 1874) -- Perseus Digital Library (same translation used for this project's citation clips; search page for exact passage)
The size of sun (and moon) and the other stars is for us what it appears to be; and in reality it is either (slightly) greater than what we see or slightly less or the same size: for so too fires on earth when looked at from a distance seem to the senses. And every objection at this point will easily be dissipated, if we pay attention to the clear vision, as I show in my books about nature. (Bailey)
[The central modern scholarly source correcting a widespread academic misreading, arguing directly against Zeller, Masson, Hicks, and Bailey: "all sensations are true" was never meant, and cannot correctly be read, as "all sensations are reliable" or infallible -- it means sensations are honestly transmitted, with error entering only in the judgment subsequently added to them.]
2. Identical Things and Indiscernibility
Epicurean physics makes duplicate bodies possible. The atoms come in a limited number of shapes, there are infinite atoms of each shape, and space and time are unlimited. Given those premises, any arrangement of atoms can occur more than once. Lucretius states that nothing in the universe is born unique, and that the very atoms which now make us up have often been in the same order before. The Epicureans did not need to deny this, and they did not deny it.
The Stoics could not accept it. Their "kataleptic" impression required every true impression to carry a mark that no false impression could share. That in turn required every individual thing in nature to be different from every other, which the Stoics credited to the skill of the divine creator. The Academic skeptics attacked exactly this point with twins, eggs, identical statues, and seal impressions. Lucullus answered that nature never makes two things exactly alike. Cicero replied that it does not matter whether two things truly differ if they cannot be told apart.
Epicurus is untouched by this argument for two reasons. (a) Identity: an identical arrangement of atoms is not the same individual. Lucretius says that even if our very atoms were gathered again in the same order, it would not be us, because the continuity of memory and life is broken. (b) Knowledge: identical bodies can produce identical sensations without any sensation being false. A sensation reports what reaches the sense organ. It carries no mark saying which individual sent it. The judgment "this is Publius and not Quintus" is an opinion, and opinions are tested by confirmation and contradiction from further evidence. Cicero himself records that of the four Academic premises against knowledge, Epicurus rejected the first, that some perceptions are false. The Stoics accepted it, and so the twins argument trapped them and not Epicurus.
This there is too that in the universe there is nothing single, nothing born unique and growing unique and alone, but it is always of some tribe, and there are many things in the same race. First of all turn your mind to living creatures; you will find that in this wise is begotten the race of wild beasts that haunts the mountains, in this wise the stock of men, in this wise again the dumb herds of scaly fishes, and all the bodies of flying fowls. Wherefore you must confess in the same way that sky and earth and sun, moon, sea, and all else that exists, are not unique, but rather of number numberless. (Bailey)
The first-beginnings of things are limited in the tale of their varying shapes. ... 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)
And so in each shape the atoms are quite infinite in number, but their differences of shape are not quite infinite, but only incomprehensible in number. (Bailey)
Furthermore, there are infinite worlds both like and unlike this world of ours. (Bailey)
Nor, if time should gather together our substance after our decease and bring it back again as it is now placed, if once more the light of life should be vouchsafed to us, yet, even were that done, it would not concern us at all, when once the remembrance of our former selves were snapped in twain. ... For when you look back over all the lapse of immeasurable time that now is gone, and think how manifold are the motions of matter, you could easily believe this too, that these same seeds, whereof we now are made, have often been placed in the same order as they are now; and yet we cannot recall that in our mind's memory; for in between lies a break in life, and all the motions have wandered everywhere far astray from sense. (Bailey)
Lastly, take any kind of corn, you will not find that every grain is like its fellows, each in its several kind, but that there runs through all some difference between their forms. (Bailey)
[Describes ordinary variety among things of a kind as evidence for the variety of atomic shapes. It does not claim that exact duplicates are impossible.]
And yet we do not grant that in this the eyes are a whit deceived. For it is theirs to see in what several spots there is light and shade: but whether it is the same light or not, whether it is the same shadow which was here, that now passes there, or whether that rather comes to pass which I said a little before, this the reasoning of the mind alone must needs determine, nor can the eyes know the nature of things. Do not then be prone to fasten on the eyes this fault in the mind. (Bailey)
If you reject any single sensation and fail to distinguish between the conclusion of opinion as to the appearance awaiting confirmation and that which is actually given by the sensation or feeling, or each intuitive apprehension of the mind, you will confound all other sensations as well with the same groundless opinion, so that you will reject every standard of judgment. (Bailey)
There are four principles which conduct you to the conclusion that there is nothing which can be known, or perceived, or comprehended; -- and it is about this that the whole dispute is. The first principle is, that some perceptions are false; the second, that such cannot be perceived; the third, that of perceptions between which there is no difference, it is not possible that some of them can be perceived and that others cannot; the fourth, that there is no true perception proceeding from the senses, to which there is not some other perception opposed which in no respect differs from it, and which cannot be perceived. Now of these four principles, the second and third are admitted by every one. Epicurus does not admit the first, but you, with whom we are now arguing, admit that one too, -- the whole contest is about the fourth. (Yonge)
And you tell us that Democritus says that there are a countless number of worlds, and that there are some which are not only so like one another, but so completely and absolutely equal in every point, that there is no difference whatever between them, and that they are quite innumerable; and so also are men. ... For why, you will say, since there not only can be, but actually are innumerable Quinti Lutatii Catuli formed out of those atoms, from which Democritus affirms that everything is produced, in all the other worlds, which are likewise innumerable, -- why may not there be a second Catulus formed in this identical world of ours? (Yonge)
Do you think that there are also innumerable other worlds, above, below, on the right hand and on the left, before, and behind, some unlike this one, and some of the same kind? And, as we are now at Bauli, and are beholding Puteoli, do you think that there are in other places like these a countless host of men, of the same names and rank, and exploits, and talents, and appearances, and ages, arguing on the same subjects? (Yonge)
[Lucullus, presenting the Stoic position of Antiochus.] First of all I reply, that you are bringing me to the arguments of Democritus, with whom I do not agree. And I will the more readily refute them, on account of that doctrine which is laid down very clearly by the more refined natural philosophers, that everything has its own separate property. ... For I have laid it down as a rule, to consider all perceptions true which are of such a character as those which are false cannot be. And from this I may not depart one finger's breadth, as they say, lest I should throw everything into confusion. ... And that must be very absurd which you sometimes are in the habit of saying, when perceptions are imprinted on the mind, that what you say is, not that there is no difference between the impressions, but only that there is none between certain appearances and forms which they assume. As if perceptions were not judged of by their appearance, which can deserve or obtain no credit if the mark by which we are to distinguish truth from falsehood be taken away. (Yonge)
You say that everything has its own peculiar genus; that there is nothing the same as something else. That is a stoic doctrine, and one not very credible, for they say that there is not a single hair or a single grain in every respect like another hair or grain. ... It has nothing in the world to do with the question whether the things which are seen do not differ at all in any part, or whether they cannot be distinguished from another even though they do differ. But, granting that there cannot be such a likeness between men, can there not be such between statues? Tell me, could not Lysippus, using the same brass, the same composition of metals, the same atmosphere, water, and all other appliances, have made a hundred Alexanders exactly alike? How then could you distinguish between them? (Yonge)
Moreover there is the supremely potent principle of infinity, which claims the closest and most careful study; we must understand that it has the following property, that in the sum of things everything has its exact match and counterpart. This property is termed by Epicurus isonomia, or the principle of uniform distribution. From this principle it follows that if the whole number of mortals be so many, there must exist no less a number of immortals, and if the causes of destruction are beyond count, the causes of conservation also are bound to be infinite. (Rackham)
And among the other reasons for marvelling at the genius of the Divine Creator is, I believe, this, -- that amid all this abundance there is no repetition; even seemingly similar things are, on comparison, unlike. God has created all the great number of leaves that we behold: each, however, is stamped with its special pattern. All the many animals: none resembles another in size -- always some difference! (Gummere)