Episode 214 of the Lucretius Today Podcast is now available. In this episode we take up Cicero's allegation that true friendship and true happiness are impossible for Epicureans.
Epicurus Letter To Herodotus -  - And if there were not that which we term void and place and intangible existence, bodies would have nowhere to exist and nothing through which to move, as they are seen to move. And besides these two, nothing can even be thought of either by conception or on the analogy of things conceivable such as could be grasped as whole existences and not spoken of as the accidents or properties of such existences. Furthermore, among bodies some are compounds, and others those of which compounds are formed.
Lucretius Book One (Bailey Edition)
 And yet all things are not held close pressed on every side by the nature of body; for there is void in things. To have learnt this will be of profit to you in dealing with many things; it will save you from wandering in doubt and always questioning about the sum of things, and distrusting my words. There is then a void, mere space untouchable and empty. For if there were not, by no means could things move; for that which is the office of body, to offend and hinder, would at every moment be present to all things; nothing, therefore, could advance, since nothing could give the example of yielding place. But as it is, through seas and lands and the high tracts of heaven, we descry many things by many means moving in diverse ways before our eyes, which, if there were not void, would not so much be robbed and baulked of restless motion, but rather could in no way have been born at all, since matter would on every side be in close-packed stillness.
 Again, however solid things may be thought to be, yet from this you can discern that they are of rare body. In rocky caverns the liquid moisture of water trickles through, and all weeps with copious dripping: food spreads itself this way and that into the body of every living thing: trees grow and thrust forth their fruit in due season, because the food is dispersed into every part of them from the lowest roots through the stems and all the branches. Noises creep through walls and fly through the shut places in the house, stiffening cold works its way to the bones: but were there no empty spaces, along which each of these bodies might pass, you would not see this come to pass by any means.
 Again, why do we see one thing surpass another in weight, when its size is no whit bigger? For if there is as much body in a bale of wool as in lead, it is natural it should weigh as much, since ’tis the office of body to press all things downwards, but on the other hand the nature of void remains without weight. So because it is just as big, yet seems lighter, it tells us, we may be sure, that it has more void; but on the other hand the heavier thing avows that there is more body in it and that it contains far less empty space within. Therefore, we may be sure, that which we are seeking with keen reasoning, does exist mingled in things—that which we call void.
 Herein lest that which some vainly imagine should avail to lead you astray from the truth, I am constrained to forestall it. They say that the waters give place to the scaly creatures as they press forward and open up a liquid path, because the fishes leave places behind, to which the waters may flow together as they yield: and that even so other things too can move among themselves and change place, albeit the whole is solid. In very truth this is all believed on false reasoning. For whither, I ask, will the scaly creatures be able to move forward, unless the waters have left an empty space? again, whither will the waters be able to give place, when the fishes cannot go forward? either then we must deny motion to every body, or we must say that void is mixed with things, from which each thing can receive the first start of movement.
 Lastly, if two broad bodies leap asunder quickly from a meeting, surely it must needs be that air seizes upon all the void, which comes to be between the bodies. Still, however rapid the rush with which it streams together as its currents hasten round, yet in one instant the whole empty space cannot be filled: for it must needs be that it fills each place as it comes, and then at last all the room is taken up. But if by chance any one thinks that when bodies have leapt apart, then this comes to be because the air condenses, he goes astray; for in that case that becomes empty which was not so before, and again that is filled which was empty before, nor can air condense in such a way, nor, if indeed it could, could it, I trow, without void draw into itself and gather into one all its parts.
 Wherefore, however long you hang back with much objection, you must needs confess at last that there is void in things. And besides by telling you many an instance, I can heap up proof for my words. But these light footprints are enough for a keen mind: by them you may detect the rest for yourself. For as dogs ranging over mountains often find by scent the lairs of wild beasts shrouded under leafage, when once they are set on sure traces of their track, so for yourself you will be able in such themes as this to see one thing after another, to win your way to all the secret places and draw out the truth thence. But if you are slack or shrink a little from my theme, this I can promise you, Memmius, on my own word: so surely will my sweet tongue pour forth to you bounteous draughts from the deep well-springs out of the treasures of my heart, that I fear lest sluggish age creep over our limbs and loosen within us the fastenings of life, before that the whole store of proofs on one single theme be launched in my verses into your ears.
 But now, to weave again at the web, which is the task of my discourse, all nature then, as it is of itself, is built of these two things: for there are bodies and the void, in which they are placed and where they move hither and thither. For that body exists is declared by the feeling which all share alike; and unless faith in this feeling be firmly grounded at once and prevail, there will be naught to which we can make appeal about things hidden, so as to prove aught by the reasoning of the mind. And next, were there not room and empty space, which we call void, nowhere could bodies be placed, nor could they wander at all hither and thither in any direction; and this I have above shown to you but a little while before.
 Besides these there is nothing which you could say is parted from all body and sundered from void, which could be discovered, as it were a third nature in the list. For whatever shall exist, must needs be something in itself; and if it suffer touch, however small and light, it will increase the count of body by a bulk great or maybe small, if it exists at all, and be added to its sum. But if it is not to be touched, inasmuch as it cannot on any side check anything from wandering through it and passing on its way, in truth it will be that which we call empty void. Or again, whatsoever exists by itself, will either do something or suffer itself while other things act upon it, or it will be such that things may exist and go on in it. But nothing can do or suffer without body, nor afford room again, unless it be void and empty space. And so besides void and bodies no third nature by itself can be left in the list of things, which might either at any time fall within the purview of our senses, or be grasped by any one through reasoning of the mind.
I will throw these in as well:
[ U74 ] Plutarch, Against Colotes, 1114A: When he proposes at the beginning of his treatise that "the nature of existence is atoms and void," he treats that nature as one, dividing it into two parts, one of them actually nothing, but termed by you and your company "intangible," "empty," and "incorporeal."
[ U75 ] Sextus Empiricus, Against the Dogmatists, 3.333: Epíkouros was in the habit of using the terms holon (whole universe) and pan (all existence) equivalently when describing the nature of bodies and of the void. For at one point he says, "the nature of the whole universe is atoms and void."
[ U76 ] Plutarch, Against Colotes, 1112E: When Epíkouros says "nature of existing things is atoms and void," do we taken him to mean that "nature" is distinct from "existing things," or simply indicate "existing things," and nothing more, just as it is his habit for instance to use the expression "the nature of void," for "void," and indeed "the nature of all existence," for "all existence?"