9 - The Final Cut: Democritus and Leucippus

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



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 on 10 March 2013

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.

Denziloe on 22 September 2013


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.

In reply to by Denziloe

Peter Adamson on 23 September 2013


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.

In reply to by Peter Adamson

Denziloe on 7 October 2013

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.

In reply to by Denziloe

Peter Adamson on 7 October 2013

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.

In reply to by Peter Adamson

Denziloe on 8 October 2013

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.

In reply to by Denziloe

Peter Adamson on 9 October 2013

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.

In reply to by Peter Adamson

Beasain on 27 June 2022

Only atoms and void

As a geochemist I can only observe that the whole universe consists only of atoms and void, and that where Aristotle refers to elasticity, this is also related to the voids between atoms that can be compressed. How a few philosophers were able to get things so right is a great mystery. The fact that air can flow around an object is also only possible because there are voids. On a subatomic level, atoms themselves are also mostly void, with only a small nucleus that consists of dense material (something like a ball in Wimbledon, where the whole stadium represents the atom).

In reply to by Beasain

Peter Adamson on 27 June 2022


Yes, I heard that comparison once too though I think with a soccer ball, not a tennis ball. (Which... seems like a big difference?) I try not to think about this sort of thing too much because I get lightheaded and need to lie down, when I should be writing podcasts.

TD on 13 March 2014

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?

In reply to by TD

Peter Adamson on 14 March 2014


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.

In reply to by Peter Adamson

Tom Sawyer on 3 April 2016


Your answers are good ones in my opinion. You might like to look at my hypothesis at new website at atomisttheory2016.net unlike 2 others I have seen online, people with books, mine is much more "purely" atomistic in that no forces are considered only mass, motion, space and time. 

Renee Vaughn on 3 May 2014

gender conundrum

I'm not as well read on philosophy as many, largely because I either can't stay awake or I get irritated by the logic of the philosophers I'm reading. So forgive my lack of knowledge in regards to the following thoughts.

It seems to me that philosophy, as a male-driven or male-remembered discipline struggles with a concept that is easier for women to comprehend. It seems that most philosophers struggles with concepts that can be expressed grammatically as I, You, We.

There is You, which is not me.
Or there is I, which is not you.
We are, but then what of You or I?

Various philosophers pick one of these assumptions and go with it..

Women tend to come from a perspective of You + I = We. All elements are essential in unity as well as individually.

Being pregnant is pretty illustrative of this.

It is difficult for women to separate mind and body simply because our bodies have a tendency to ignore our minds and because our minds are so involved with what is going on with our bodies. ( Audre Lord wrote an interesting essay on Eroticism which goes into this more poetically: http://www.metahistory.org/guidelines/EroticUses.php )

Not having ever been a man, I've no idea what it's like to be one but it does seem that there is a basic difference of presupposition between the sexes.

Admittedly my thoughts are heavily influenced by my work as a relationship coach! So maybe I've no clue.

In your experience, have you found gender differences in philosophy/philosophers? What are your thoughts?

In reply to by Renee Vaughn

Peter Adamson on 4 May 2014


Well, I think that is a keenly disputed issue in recent philosophy of gender - whether there are particular philosophical approaches or ways of thinking that are "gendered" either male or female. Is see where it is coming from but this idea makes me a bit nervous - it so easily slides into people thinking stupid things like "women can't do logic properly" or "men can't think properly about emotions." Actually I touch on this issue in one of the added chapters included in the new "Classical Philosophy" book just coming out, based on the earliest podcast episodes. The chapter includes a short discussion of Julia Kristeva's discussion of Aristotle on place which makes some points akin to what you are saying.

In reply to by Peter Adamson

Renee Vaughn on 4 May 2014


I agree- it can lead to really stupid and hurtful dialogue. Perhaps a better way of addressing the issue is to ask how a person's connection to their physical body affects their thinking.

The Mind bias in philosophy has always bothered me because it has led to such a disjoint between humanity and the natural world as well as between genders.

It's too bad there aren't records of women classical philosophers to see what they would have come up with in the way of explaining being. I'll have to dig around to see what modern philosophical thought says about it all.

The other interesting thing is that gender is fluid now. I can't wait to see how transgenderism affects philosophy and thus culture and politics.

Thank you for tiptoeing around the issue so well. I'd hate to turn this great forum into a mosh pit.

In reply to by Renee Vaughn

Peter Adamson on 4 May 2014

body and thinking

I agree, that's a very interesting way of looking at it - one could extend the idea, for instance do people's philosophical views change (or tend to change) if their bodies are e.g. elderly or blind? Actually there is a skeptical strategy used by ancient Skeptics like Sextus (see episode 73) which suggests that a claim like "honey is sweet" will be true for the healthy person but false for the ill person, who finds honey bitter. And the idea is that this creates a dispute about whether honey is by nature in fact sweet. One could extend that point to suggest that in general people's bodily circumstances affect their beliefs, not only about philosophy but about a whole range of issues. And certainly it isn't implausible that a really extraordinary physical experience, like being pregnant, could change one's understanding or give one insights that would be difficult or even impossible for someone who had never had the same experience. On the other hand I think we shouldn't underestimate the power of the human mind to imagine its way into the experiences of other people - great novelists/playwrights, and also great philosophers like Plato, seem able to do this, and I feel it is part of what makes them great. (How many male novelists write really convincing female characters? Not many... but some manage it.)

In reply to by Peter Adamson

Renee Vaughn on 4 May 2014

That's what so confusing

That's what so confusing about bigotry, actually any sort of judgment- no one can really know what it is to be anything else. We can imagine, we can ask, but no way will we be able to experience it.


Lions, tigers and bears.

I agree with your analysis of the Greats. I think as long as you can grasp something else's worldview enough to empathize with it then you have the unification of parts that could be called whole.

Your post makes me think of Justin Norton's Phantom Tollbooth in which a group of characters grow from the head down- their feet float- so their world view never changes.

And so on to Empedocles for me!

In reply to by Peter Adamson

TD on 4 May 2014

Most female and male minds are the same at least in one respect

Assuming there are no mental defects preventing it, both female and male minds can both reason.

Both men and women will always agree 1+1=2 if we are thinking and reasoning mathematically.

Isn't reason the great liberator and leveller for all, emotion the great enslaver.

In reply to by TD

Renee Vaughn on 4 May 2014

Emotion combined with reason

Emotion combined with reason is more powerful than either on their own. I think Socrates talks about emotion being the horse and reason being the jockey.

Being in the flow is a good example of the mind working well with the emotions. What the jockey does with all that power is what makes a Kentucky Derby winner but without the horse, he's a slow biped.

Isn't there something about memory only gets stored if it is emotionally relevant?

There's a great book called Deep Survival by Laurence Gonzales that talks about this.

But I agree that when it comes down to agreed upon facts (assuming we all agree on what 1, +, = and 2 mean), there is no real gender difference. Maybe it's just a matter of getting to the same place in different ways and doing different things with it when we get there.

In reply to by Renee Vaughn

Peter Adamson on 4 May 2014

Emotion as a horse

Yes, that's in the Phaedrus - the image is actually slightly more complicated, it is a charioteer (presumably representing reason) steering two horses, one wild and problematic and one noble. These probably represent the two lower souls (desire and spirit) from the Republic. (It's not clear that either of these is exactly "emotion", which is perhaps a problematic term to apply to ancient Greek psychology.) I talk about the Phaedrus in episode 31 by the way.

In reply to by Renee Vaughn

TD on 6 May 2014

The Rational Man?

I have read studies showing emotion aids in memory retention, just as you've said. Perhaps even things like Ritalin work by agitating emotion.

Yes it seems you would need both as I've implied in another post in the Sophistry comment section. Doesn't Plato explain this in the Republic's Tripartite Soul section?
Isn't it true that when emotion rules over our reason we get the empirical evidence we see today and in posterity; race wars, religious wars, economic wars or male and female chauvinism, gay and straight confrontations, obesity and starvation epidemics.

Now what was it that Bertrand Russell said about the rational man?

Kenneth on 27 October 2014

String Theory

When you started talking about the infinite worlds that represent a different arrangement of atoms, that reminded me of string theory. This is actually a serious subject inside physics that attempts to explain why electrons act like both a wave and a particle. The problem arose from the famous double slit experiment. Electrons act like a wave when unobserved but any attempt to observe the electron and it behaves like a particle.
It is almost comical to listen to physicists wrestle with the philosophical question: if a tree falls in a forest....
String theory attempts to resolve this mystery by saying that the electron goes through the slits in an infinite number of ways, but when it is observed, it only goes through in one specific way. SO, there are infinite universes in which the atom/electron goes through the slits in many different ways, but observation makes it so the observed way is the universe in which we observe it. Sounds a little crazy to me, the point is though, Physicists seem to returning to the Atomists by saying that there are alternate universes, and this one only exists for us because we observe it.
String theory=modern infinite world theory.

Stephen on 6 August 2016

Electrons make Final Cut?

Peter, may I make one small correction to the first part of your excellent podcast on the Atomists. I'm no expert, but as far as I know Electrons are indeed indivisible: they have no internal structure and have the lightest possible masses for charged particles, so can't be reduced to something smaller. The Quarks that compose protons and neutrons also seem to have made the 'final cut'. 

I think Leucippus and Democritus would be delighted with the simplicity and economy of modern particle physics. To explain the diversity of substances in the visible world they had to posit an infinite variety of 'atoms', but now everything in the universe, from giraffes to galaxies, can be reduced to just three fundamental particles: electrons, up-quarks and down-quarks. Two ups and a down make a proton,  two downs and an up, and that's a neutron. Even the diversity of atomic elements is just a numbers game, the quantity of identical protons in the atomic nucleus, orbited by an equal number of identical electrons.

Of course they would be less comfortable with other aspects of modern theory, particularly the loss of atomic immortality. That seems to have transferred to conserved properties, like energy and momentum. Particles may persist for billions of years, but are vulnerable to annihilation due to extreme pressure, collisions etc. What would they make of the LHC?

Hope this helps.


In reply to by Stephen

Peter Adamson on 8 August 2016


Ok, I'll yield to you on the question of whether electrons can actually be split; but there is also an issue here about whether they have parts and I take it that subatomic particles do have parts even if they cannot be actually divided. Of course ancient atomists could and sometimes did admit that atoms are indivisible yet do have parts, too.

Jordan White on 18 May 2017


Just wanted to drop a thank you in here for undertaking this. I seem to have discovered this awesome and ambitious project about 7 years since it begun. Great resource for those of us who need a good overview before we jump into the books. Thank you!

In reply to by Jordan White

Peter Adamson on 18 May 2017


Great, glad you found it! Hope you will enjoy the rest of the series.

Jane on 15 December 2018

Enduring relevance of the atom

Is it not that the atomists indivisible unit with its own particular “shape” and capacity for interaction represents, in today’s understanding, the smallest unit of an element beyond which any further division obliterates the elemental unit? and currently this smallest unit can be defined by the number of protons within the atomic nucleus? The fact that the atom of an element can be divided into parts is essentially irrelevant to its functioning as a particular element, irrespective of the fact that said parts enable functionality.

Is this not similar to the relevance of Newtonian physics in an era of quantum mechanics? What would be left of Chemistry as a field of understanding if the atom, as indivisible, no longer defined the element?

In reply to by Jane

Peter Adamson on 15 December 2018


To some extent your question exceeds the bounds of what I can comment on, since I am no expert on modern day atomic physics. But I would at least point out that ancient atomism is derived solely from conceptual analysis: it had (and at the time could have had) no empirical support, but was just based on arguments about division of bodies need to work. So that is a big difference. Also their conception of a physical atom was obviously very, very different from a modern day atom: they are really just very small bodies that cannot be divided but in other respects like the familiar bodies that surround us, whereas modern day atoms are surpassingly strange from an everyday object point of view.

Still of course you're right that their view is in other ways startlingly close to being "right" and there is no harm in celebrating that!

In reply to by Jane

Karl Young on 16 December 2018


While you have a point re. "The fact that the atom of an element can be divided into parts is essentially irrelevant to its functioning as a particular element..." it seems you're statement can equally well be be turned around re. "the functioning of a particular element is essentially irrelevant to whether it is fundamental or can be divided into parts". And, idle or not, it seems to me that whether something is fundamentally divisible or not was a basic concern of the atomists as well as modern particle physicists (though as Peter's comment hints at, modern particle physicists have a few tools in addition to the conceptual analysis of the ancient atomists). And not that details matter much, but according to currently held physical models, the most elemental units of a nucleus are quarks and gluons (protons and nuetrons are composites of these).    

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