Lucretius Today Podcast 120 – Letter to Herodotus 9 – Epicurus’ Rejection of Infinite Divisibility

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Welcome to Episode One Hundred Twenty of Lucretius Today. This is a podcast dedicated to the poet Lucretius, who wrote “On The Nature of Things,” the only complete presentation of Epicurean philosophy left to us from the ancient world. I am your host Cassius, and together with our panelists from the forum, we’ll walk you through the ancient Epicurean texts, and we’ll discuss how Epicurean philosophy can apply to you today. We encourage you to study Epicurus for yourself, and we suggest the best place to start is the book “Epicurus and His Philosophy” by Canadian professor Norman DeWitt. If you find the Epicurean worldview attractive, we invite you to join us in the study of Epicurus at, where you will find a discussion thread for each of our podcast episodes and many other topics. Today we continue our review of Epicurus’ letter to Herodotus, and we move further into fundamental physics and discuss issues related to the question of whether matter can be infinitely divided.

Now let’s join Joshua reading today’s text:


Moreover, we must not either suppose that every size exists among the atoms, in order that the evidence of phenomena may not contradict us, but we must suppose that there are some variations of size. For if this be the case, we can give a better account of what occurs in our feelings and sensations.

[56] But the existence of atoms of every size is not required to explain the differences of qualities in things, and at the same time some atoms would be bound to come within our ken and be visible; but this is never seen to be the case, nor is it possible to imagine how an atom could become visible.

Besides this we must not suppose that in a limited body there can be infinite parts or parts of every degree of smallness. Therefore, we must not only do away with division into smaller and smaller parts to infinity, in order that we may not make all things weak, and so in the composition of aggregate bodies be compelled to crush and squander the things that exist into the non-existent, but we must not either suppose that in limited bodies there is a possibility of continuing to infinity in passing even to smaller and smaller parts.

[57] For if once one says that there are infinite parts in a body or parts of any degree of smallness, it is not possible to conceive how this should be, and indeed how could the body any longer be limited in size? (For it is obvious that these infinite particles must be of some size or other; and however small they may be, the size of the body too would be infinite.) And again, since the limited body has an extreme point, which is distinguishable, even though not perceptible by itself, you cannot conceive that the succeeding point to it is not similar in character, or that if you go on in this way from one point to another, it should be possible for you to proceed to infinity marking such points in your mind.

[58] We must notice also that the least thing in sensation is neither exactly like that which admits of progression from one part to another, nor again is it in every respect wholly unlike it, but it has a certain affinity with such bodies, yet cannot be divided into parts. But when on the analogy of this resemblance we think to divide off parts of it, one on the one side and another on the other, it must needs be that another point like the first meets our view. And we look at these points in succession starting from the first, not within the limits of the same point nor in contact part with part, but yet by means of their own proper characteristics measuring the size of bodies, more in a greater body and fewer in a smaller.

[59] Now we must suppose that the least part in the atom too bears the same relation to the whole; for though in smallness it is obvious that it exceeds that which is seen by sensation, yet it has the same relations. For indeed we have already declared on the ground of its relation to sensible bodies that the atom has size, only we placed it far below them in smallness. Further, we must consider these least indivisible points as boundary-marks, providing in themselves as primary units the measure of size for the atoms, both for the smaller and the greater, in our contemplation of these unseen bodies by means of thought. For the affinity which the least parts of the atom have to the homogeneous parts of sensible things is sufficient to justify our conclusion to this extent: but that they should ever come together as bodies with motion is quite impossible.

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