9 - The Final Cut: Democritus and Leucippus

In this episode Peter discusses the Atomists Democritus and Leucippus, and how they were responding to the ideas of Parmenides and his followers.

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Further Reading: 

D. Furley, “Two Studies in the Greek Atomists,” (Princeton: Princeton University Press, 1967).

P.S. Hasper, “The Foundations of Presocratic Atomism,” Oxford Studies in Ancient Philosophy 17 (1999), 1-14.

D. Konstan, “Atomism and its Heritage: Minimal Parts,” in Ancient Philosophy, 2 (1982), 60-75.

T. O’Keefe, “The Ontological Status of Sensible Qualities for Democritus and Epicurus,” Ancient Philosophy 17 (1997), 119-34.

C.C.W. Taylor, The Atomists: Leucippus and Democritus (Toronto: 1999).


Stanford Encyclopedia: Democritus

Stanford Encyclopedia: Ancient Atomism

samuel's picture

Periodic tables and abstract thinking

Before anything I'd like to thank you for your consistent work, which I find interesting to the point of being addictive.
I simply mean to add a remark about the method involved in the designing of the periodic table, with some correlation to what you say, towards the end of this podcast, about scientific theories being an extensions of our everyday experience.

When Mendeleïev first desgined the periodic table, he did it with great emphasis on method. According to the structure of the table, there should have been a given and relatively small number of observable chemical elements in the universe. But one of those elements was missing, there was no empirical evidence of its existence. Instead of dismissing his table, Mendeleiev took the bold step of sticking with his theory, and said that the table told us the missing element must exist, albeit still unobserved. This element, named Gallium, was discovered years, or even decades later. Mendeleiev had actually managed to predict the existence of an element with a sheer theoretical argument.

I find this to be quite reminding of Parmenides's way of thinking in some way: if the senses won't tell you the truth, you should rely on the mind only. But like Parmenides had the Way of Opinion besides the way of Truth, Mendeleiev had built his table on empirical datas before making it a distinctly structural tool.

Imran Ahmed's picture


That's an interesting comment, thanks.

Denziloe's picture


Some elaboration of the positive arguments which led these thinkers to atomism would have been welcome... I find it fascinating that these ancients believed in and enunciated a theory of the world so totally disjoint from our immediate (continuous) experience (and yet, of course, ultimately correct). Bertrand Russel called it a lucky guess but I think there's more to it than that.

Peter Adamson's picture


Unfortunately we're better informed about the pro-atomistic arguments of Epicurus than of Democritus and Leucippus (see the relevant Epicureanism episode). I think the main argument is just the impossibility of infinite division, though.

Denziloe's picture

Ah, I haven't reached

Ah, I haven't reached Epicurus yet. Thanks!

I didn't expect such diligent patronage of your comments section; can I take the opportunity to say 'thank you' for this excellent resource. Your hard work and lucidity are super appreciated! Please don't stop!

What, may I ask, is your personal stance on the epistemological soundness of (let's say the best of) the Atomists' arguments?

Personally I suspect that, while the microscopic continuity of our universe would not be internally inconsistent, nor externally inconsistent with our macroscopic observations, there may be a strong case to be made for some of the Atomists' arguments to be regarded as correct from a contemporary empirical viewpoint, in particular when viewed as an induction from the ubiquitous macroscopic observation that no material ever spontaneously comes into, or passes out of, existence.

Peter Adamson's picture

How good are the atomists' arguments?

Glad you are enjoying the series! In response to your question, I think Aristotle is right that sense perception doesn't really settle the issue as to whether void is required for motion to be possible, which might be their most persuasive point. As far as our everyday experience goes, we could I think explain motion by invoking the mutual replacement of bodies, as when I move through air and the air gets pushed around and fills in behind me -- no empty space is required, so long as things are capable of moving other things out of the way. Admittedly, that may depend on variations in density, and Aristotle thinks that things can be more or less dense without involving void -- I'm not sure that raw sense experience settles that issue one way or another.

Of course the other issue is whether infinite division is in principle possible, and again, I don't really see how sense perception settles this issue. So, on balance (and without getting far more deeply into this, as one really should if one wanted to assess the position properly) I'd say that Epicurus is being over-confident about what sensation can establish.

Denziloe's picture

How good are the atomists' arguments?

I agree about void - Aristotle's objection was the same one I had the moment I heard the argument! Fascinating how much intuitive objection there was to this idea, right up to the point where Toricelli made a void in his lab - and contemporary culture feels no such repugnance.

With respects to division, I could have been more clear. What I meant was that we never observe substance appearing from nothing or disappearing into nothing (and though we now know this isn't universally valid, e.g. the Big Bang or quantum mechanics, it is indeed valid from chemistry and upwards) - but that we also observe substances changing, such as from ice to water. If we assert that these are, at the fundamental, infinitesimally small level, totally different stuffs, there's a tension between the two observations, because one substance is disappearing from existence and another appearing from nonexistence.

Of course, observation can never decisively settle any issue (thanks for that, Hume), but I can't help but feel the Atomists' arguments might have some real weight, insofar as any inductive argument has weight.

Peter Adamson's picture

Empiricism and atomism

Yes, I agree - it's always interesting to see what people in other historical periods thought was "obviously" false (another nice example is whether light travels, Aristotle says it is patently clear that it doesn't).

On your second paragraph, this reminds me of what Aristotle says about atomism namely that the atomists fail to understand that there can be qualitative change. So, although he would agree with them (and you) that we never see anything just pop into or out of existence, he thinks that things can persist _through_ changes as when a stone heats up. Whereas the atomists assume that all change needs to be rearrangements of inviolable bodies.

TD's picture

Democritus please tell me

Democritus please tell me what is it that allows one atom to interact with another?

Now if atoms are the smallest things in the universe is there another atom in-between these two atoms which allows them to interact?

Surely there must be something common between the two atoms allowing them to interact.

When you say void, do you mean non being? If non being how can we conceive of non being when it doesn't exist? When I take a glass off a table what replaces the glass? Is it void that replaces it and does the void disappear where I put the glass down?

Peter Adamson's picture


Those are good questions. The first thing you are saying was in fact put forward in antiquity as an objection to atomism; the idea seems to be that they can come into contact and interact that way, which suggests that they have parts (so the left part of one might touch the right part of another) allowing them to bounce off one another. But if they have parts aren't they divisible? This sort of reason might underlie the atomist proposal that atoms do have minimal parts but cannot be divided apart into them.

The second question is perhaps easier for them: void is indeed non being or emptiness. They think that motion requires non-being, so that there is something to move into. Melissus the Eleatic uses this reasoning to show that motion is impossible since it is absurd to assert the existence if non-being. The atomists go the other way: obviously there is motion, so there is also non-being to make motion possible. And this is void. It is tempting to think of the void as space that can be occupied or not, depending on whether an atom is present at a given moment. But that is probably anachronistic.