Posts by Cassius

Thanks for your question, Dave. It comes up frequently so I have updated the FAQ. Here's the short version:

Epicurus would be the last person to insist we cling to 2,000-year-old technical details in physics just because he said them. He was emphatically committed to observation and experience over authority — including his own. So when you say modern physics has advanced what Epicurus encouraged, I agree completely. The question is really: what specifically did Epicurus encourage in the area of physics, and why does it still matter to how we live?

Here's the crux: Epicurean physics was never really about the technical details of atoms for their own sake. It was constructed to do a specific job — to address three towering sources of human misery:

1. The fear that supernatural gods are watching us, judging us, and will punish us after death.

2. The fear that the universe is governed by Fate or Necessity, that nothing we do matters, and that we have no real agency in our own lives.

3. The view that what we see around us is not real, and that our lives and everything we value is essentially 'unreal."

Epicurus built his physics — the atoms, the void, the swerve, the emergent properties of compound things — specifically to establish that the natural world we experience is self-sufficient and self-explanatory. Nothing comes from nothing; nothing goes to nothing; the universe operates by natural processes, not divine whim or iron destiny. That framework is what allows the ethics to work. Pull out the physics, and you immediately create space for the supernatural to rush back in — which is exactly what Epicurus' rivals (Plato, the Stoics, and later the Christians) did with great success.

Now, as to the Sedley article specifically — and the question of whether Epicurus was a "reductionist" — this turns out to be very relevant to modern Epicurean life, more than it might first appear. Sedley's argument is that Epicurus was not a strict reductionist: he did not say that your feelings of pleasure and pain, your lived experience, your psychological states are "mere illusions" that dissolve into atomic physics if you look closely enough. The qualities of compound things — including the pleasure and pain we feel — are real, not eliminable, and must be understood at their own level. That is philosophically powerful ammunition against the modern dismissal of Epicurean ethics as "merely subjective" or "just brain chemistry."

So the short answer to your question "why should I care about the atoms debate if so much science has changed?" is: care not because the technical atomic details are sacred, but because the method and framework Epicurus established — natural causation, no supernatural intervention, emergent reality at the level of lived experience — is exactly what you need to build and defend a life philosophy grounded in nature. And you need confidence in a framework that establishes that your life and the things you value are truly real. The details update as science advances; the framework remains as essential as it ever was.

The full updated FAQ answer is here:

Why Should I Care About Epicurean Physics When So Much Science Has Changed in the Last 2,000 Years? - Epicureanfriends.com

www.epicureanfriends.com

Eikadistes I thought of your article in reading David Sedley's "Epicurean Anti-Reductionism," and I wanted to be sure you saw this.

I don't recall all the details of your article, but I think you'd find the concluding section of Sedley's article supportive of the argument that Epicurus should really not be considered primarily an atomist.

The following is a quotation translated by David Sedley from Epicurus' On Nature 34.21-2. It comes from Sedley's discussion of "Downward Causation" in how the mind itself can influence the atoms. There are numerous implications that can be drawn from it but to my observation it's not a well-known quote so I therefore give this its own thread. The clip comes from Sedley's "Epicurean Anti-Reductionism" page 319.

In this article Sedley refers several time to aetiology and ontology and discusses which aspect is primary to Epicurus on a particular point. It might help to have this explanation before reading the article (pasted from our good friends at ChatGPT):

The phrase “aetiologically rather than ontologically primary” distinguishes two different senses in which something can be considered “primary” or fundamental.

1. Aetiologically primary (causally primary)

• Aetiology means cause or explanation of origin.
• If something is aetiologically primary, it is:
  • The cause or source of something else
  • What explains how or why something comes to be

👉 In simple terms:
It comes first in the order of explanation or causation.

2. Ontologically primary (being primary)

• Ontology concerns what exists and what is fundamentally real.
• If something is ontologically primary, it is:
  • More fundamental in reality
  • What other things depend on for their existence

👉 In simple terms:
It comes first in the order of being or reality.

This topic was also discussed in a recent zoom meeting. The answer appears debatable, and I see that Sedley's article "Epicurean Anti-Reductionism" has this to say (see especially footnote 29):

Here is the translation from Demetrius Lacon cited on page 306:

There's a LOT of interest in that article. Here's a section that both interesting and "funny" as to what should probably be our love-hate relationship with Cyril Bailey:

From the Sedley Article "Epicurean Anti-Reductionism"

We've referenced many times on the forum the comments about this topic made by David Sedley in his "Epicurus' Refutation of Determinism."

I don't think we previously cited - or that I knew of - an article Dr. Sedley had written directly on point:

Epicurean Anti-Reductionism - 1988 - J. Barnes, M. Mignucci (eds.), Matter and Metaphysics (Naples 1988), 295-327

Full article available here:

Epicurean anti-reductionism

Epicurean anti-reductionism

www.academia.edu

Summary of Main Arguments and Highlights

1. Core Thesis: Epicureanism is Not Fully Reductionist

Sedley’s central claim is that Epicurean philosophy, although grounded in atomism, cannot be understood as a purely reductionist system.

• While everything is composed of atoms and void, Epicurus does not reduce all explanations to atomic properties alone.
• Instead, Epicureanism allows for higher-level explanations that are not eliminable into micro-level physics.

Key implication:
Epicurus is a qualified materialist, not a strict reductionist.

2. Distinction Between Atoms and Compounds

Sedley emphasizes a crucial distinction:

• Atoms: possess only a few immutable properties (shape, size, weight).
• Compound bodies: exhibit qualities that do not belong to atoms themselves.

This aligns with Lucretius’ distinction between:

• Coniuncta (necessary qualities)
• Eventa (accidental qualities)

These qualities:

• Depend on atomic arrangements
• But are not reducible to atomic descriptions

3. Emergent Qualities Are Real (Not Illusions)

A central anti-reductionist point:

• Qualities like color, heat, solidity, life, and agency are:
  • Not properties of individual atoms
  • Yet genuinely real features of compound bodies

Sedley stresses that Epicurus:

• Does not treat these as mere appearances or illusions
• Instead treats them as objective, though derivative, realities

Conclusion:
Epicureanism supports a form of emergence—higher-level properties arise from but are not identical to lower-level constituents.

4. Explanatory Pluralism

Sedley argues that Epicurus uses multiple levels of explanation simultaneously:

• Micro-level: atoms and their motions
• Macro-level: observable phenomena and qualities

These levels are:

• Compatible, but
• Not interchangeable

Thus:

• Some explanations are best given at the level of bodies, not atoms.

5. Rejection of Eliminative Reductionism

Epicurus rejects the idea that:

Quote

Only atomic-level facts are “really real”

Instead:

• Observable properties retain explanatory legitimacy
• Everyday descriptions (e.g., “fire is hot”) are philosophically valid

This is a direct rejection of:

• The view that higher-level properties must be eliminated in favor of physics

6. Stability and Identity of Objects

Sedley highlights that:

• Compound bodies have stable identities
• These identities depend on:
  • Structural organization
  • Functional roles

Not merely:

• A list of atomic constituents

Thus:

• A thing’s identity is tied to its emergent organization, not just its atoms

7. Ethical and Psychological Implications

This anti-reductionism is not merely physical—it extends into ethics:

• Human experiences (pleasure, pain, fear) are:
  • Grounded in atomic processes
  • But must be understood at the level of lived experience

Epicurus therefore:

• Treats psychological states as real and explanatorily significant
• Not reducible away into physics

8. Lucretius as Key Evidence

Sedley relies heavily on On the Nature of Things to support this interpretation:

• Lucretius explicitly distinguishes:
  • Atomic properties
  • Emergent qualities of bodies
• He shows that:
  • Qualities arise from arrangements and interactions, not intrinsic atomic features

Overall Interpretation

Sedley’s interpretation can be summarized as follows:

• Epicurus is a materialist → everything is made of atoms and void
• But also an anti-reductionist → not everything can be explained purely at the atomic level

This results in a philosophical position that combines:

• Ontological reduction (everything is atoms)
• With explanatory pluralism (not everything is explained in atomic terms)

Concise Takeaway

Quote

Epicurean philosophy holds that while atoms are the fundamental constituents of reality, the world we experience—including qualities, objects, and human life—must be understood at their own level and cannot be reduced away into atomic descriptions.

Among the topics we discussed in a zoom last night was what does Epicurus say about atomic size whether there a finite range of atomic sizes? The following is AI so take it only as a possible starting point.

Atomic Size (μέγεθος) in the Letter to Herodotus

What Epicurus Actually Says (§§55–56, 58–59)

Epicurus establishes two constraints on atomic size that work in opposite directions, producing a finite range:

Lower bound — atoms are not infinitely small: Atoms cannot be arbitrarily tiny because they must be composed of a minimum number of minimal parts (ἐλάχιστα). The atom is the smallest composite body — it has parts that are conceptually distinguishable as minima, even though those parts cannot exist independently. This is the famous theory of minimal parts, developed in part to answer Zeno's paradoxes of infinite divisibility. An atom of one minimum part would be a mathematical point, not a physical body.

Upper bound — atoms are not perceptible: Epicurus states explicitly that no atom is ever large enough to be seen (§55). If atoms were perceptible in size, we would observe them. We do not. Therefore their sizes must fall entirely below the threshold of perception.

The relevant sentence from §55 (paraphrased): atoms have size, shape, and weight, but no quality that perception can grasp — they cannot be seen, tasted, or touched as individual atoms.

Why a Finite Range of Sizes?

The argument runs something like this:

1. Atoms differ in size (this is required to explain why compounds differ — identical atoms could not produce variety).
2. But the variation is bounded: there is a smallest possible atom (a body with the fewest possible minimal parts, probably one or two) and a largest possible atom (still sub-perceptible).
3. Therefore the range of atomic sizes is finite in number of types, even if the number of individual atoms within each size-type is infinite.

Epicurus makes this explicit: the varieties of atomic shapes are not infinite in number, only incomprehensibly large (§42). The same logic applies to sizes. An actual infinity of size-types would create serious problems — it would allow for atoms large enough to be perceptible, which contradicts the evidence of experience.

Sedley's Analysis

Sedley (Lucretius and the Transformation of Greek Wisdom, 1998, and "Epicurean Anti-Reductionism," 1988) emphasizes that the minimal parts doctrine is Epicurus' own innovation, not found in Democritus. For Democritus, atoms could in principle be any size — Epicurus constrains this by grounding atomic structure in a discrete geometry of minima. This gives the size property a quasi-mathematical character: atomic size is not a continuous variable but a discrete one (how many minima make up this atom?).

This is philosophically significant because it means μέγεθος, unlike the emergent qualities of compounds, is intrinsic, immutable, and countable — which is precisely why it qualifies as a genuine property of atoms rather than a quality in the coniuncta/eventa sense.

Lucretius' Parallel Account

Lucretius covers this in DRN 1.599–634 (the finitude of atomic shapes) and implicitly throughout Book 2 (2.333–380 on size variation explaining sensory differences). He does not invoke the minimal parts argument as explicitly as Epicurus does, but the upper bound — atoms are always invisible — is stated clearly and used to explain why the world appears continuous even though it is granular.

Summary Table

The elegance of Epicurus' position is that both constraints are empirically motivated: one by the fact that matter is physically real (not geometric abstraction), the other by the fact that atoms are never observed directly. The finite range of μέγεθος is thus not a mathematical stipulation but a conclusion drawn from two independent observations about the nature of physical reality.

Last night in our zoom the question came up as to whether Epicurus held that atoms differ in weight. This is what AI has to say - take it for what its worth and let's discuss whether they differ in weight or not.

Atomic Weight (βάρος) in Epicurean Philosophy

Does Epicurus say atoms have different weights?

Yes — but with important qualifications. Epicurus lists weight alongside size and shape as one of the three intrinsic properties of atoms. However, the relationship between weight and the other properties is philosophically murky in ways that size is not.

The key passage is Letter to Herodotus §54: atoms differ in shape, size, and weight (βάρος). This seems straightforward. But complications arise immediately.

The Upper and Lower Bound Problem for Weight

Lower bound — every atom has some weight: This is unambiguous. Epicurus breaks decisively from Democritus here. Democritus did not attribute weight to atoms as an intrinsic property — weight for him was a relational or emergent phenomenon arising from atomic collisions and vortex motion. Epicurus insists weight is primitive and intrinsic: every atom, no matter how small, has weight, and weight is what drives the fundamental downward motion through the void (the clinamen aside). There is no weightless atom. So the lower bound is: at least some minimal quantum of weight, corresponding presumably to the smallest atom.

Upper bound — here it gets complicated: Unlike size, where Epicurus gives a clear upper bound (atoms must remain sub-perceptible), he does not give an equally crisp upper bound for weight in the Letter to Herodotus. The constraint that seems to apply is:

1. Weight must correlate at least roughly with size (a larger atom, having more minimal parts, should be heavier).
2. Since atomic size is bounded above by sub-perceptibility, atomic weight is indirectly bounded — an atom cannot be so heavy that it produces perceptible gravitational effects in isolation.
3. But Epicurus never states this explicitly for weight the way he does for size.

The Lucretius Complication

This is where things get genuinely difficult. Lucretius, in DRN 2.225–242 and 2.333–380, appears to deny that atoms differ in weight at all — or at least to deny that heavier atoms fall faster than lighter ones. His argument for the clinamen (the atomic swerve) depends on all atoms falling at the same speed in the void regardless of weight. This is the famous passage: in empty space, a feather and a lead ball fall at the same rate — only resistance (plagae) from surrounding matter creates apparent differences in falling speed.

This produces an apparent contradiction:

• Epicurus says atoms have different weights (βάρος varies).
• Lucretius says all atoms fall at the same speed.

How scholars resolve this:

Sedley (Lucretius and the Transformation of Greek Wisdom, 1998) argues these are not actually contradictory. Atoms have different quantities of weight, but in the infinite void with no resistance, the rate of fall is uniform regardless — because there is no medium to create differential drag. Weight differences matter only when atoms are in collision with other atoms, contributing to the mass and downward tendency of compound bodies. The weight of an atom is real but its effect on velocity is masked by the homogeneity of the void.

Bailey and others have argued more skeptically that Lucretius may simply be softening or misrepresenting Epicurus on this point.

Does Weight Scale with Size?

This is another contested question. The natural assumption is that a larger atom (more minimal parts) is also heavier. Epicurus seems to assume this, but he never makes it explicit. The problem is that shape also varies independently of size — a very intricately shaped atom might have more minimal parts than a compact spherical atom of the same overall dimensions. Weight, size, and shape are listed as independent variables in §54, which suggests they can vary independently of each other — a philosophically awkward result if weight is just a function of volume.

Summary of Constraints

The sources available to us are less developed than treatment of size. The minimal parts doctrine gives size a rigorous lower bound with clear mathematical structure. Weight by contrast seems to be asserted as a primitive intrinsic property largely to explain why atoms move at all — and the upper bound problem is left more implicit than resolved.

Another option:

Sedley's Routledge Encyclopedia entry (2005) states that "atoms themselves have only the primary or ineliminable features of body: size, shape and weight," and that the ground for this parsimony is the Letter to Herodotus §54–55: secondary properties are changeable by nature, whereas atoms are the enduring entities underlying change. Routledge Epicurus avoids the "reductionism" of Democritus — while everything is ultimately atoms and void, the emergent properties that arise from those combinations are not equivalent in every respect to their constituent atoms.

On the compound-body level, Lucretius distinguishes in De Rerum Natura properties that are inseparable (coniuncta, Greek συμβεβηκότα) from others that are accidental (eventa, συμπτώματα). Stanford Encyclopedia of Philosophy And crucially on the ontological status of those emergent qualities: although colors and other accidents are real, they are irreducibly different from atomic structures, and atomic structures are in no way ontologically privileged over the phenomenal level — neither level has a monopoly on truth. Routledge

Here is the main structural diagram showing the full ontological hierarchy:

Again - consider these as initial drafts that will need further revision!

In our Zoom of 3/25/26 we discussed the topic of this thread and how it would be desirable to prepare a diagram / explanation of the proper use of these terms. Bryan has by far the best command of this and he has provided some basic information from which it would be desirable to come up with more explanatory material. Here are two charts of the words in issue, followed by an initial effort using an AI generator to make a diagram. Consider this just a starting point and not by any means authoritative, and let's see what we can do to produce a clear explanation.

J.Tycherne tells us -

Quote

Hi Cassius,

Thanks very much for your tentative approval of my account. I'm just getting started learning about Epicurus and am very interested to learn more. I started by reading Diogenes Laertius' Book X on Epicurus, and found myself very much interested in Epicurean thought, particularly his letter to Menoikeus. I can read Greek, but am self-taught so am no scholar. I found myself frustrated by the Loeb translation of this letter, so was searching for other English translations, and stumbled upon your site. I've already found a translation uploaded by one of the other users here, which I plan to get into presently.

j.tycherne

Welcome j.tycherne

There is one last step to complete your registration:

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Please say "Hello" by introducing yourself, tell us what prompted your interest in Epicureanism and which particular aspects of Epicureanism most interest you, and/or post a question.

This forum is the place for students of Epicurus to coordinate their studies and work together to promote the philosophy of Epicurus. Please remember that all posting here is subject to our Community Standards and associated Terms of Use. Please be sure to read that document to understand our ground rules.

Please understand that the leaders of this forum are well aware that many fans of Epicurus may have sincerely-held views of what Epicurus taught that are incompatible with the purposes and standards of this forum. This forum is dedicated exclusively to the study and support of people who are committed to classical Epicurean views. As a result, this forum is not for people who seek to mix and match Epicurean views with positions that are inherently inconsistent with the core teachings of Epicurus.

All of us who are here have arrived at our respect for Epicurus after long journeys through other philosophies, and we do not demand of others what we were not able to do ourselves. Epicurean philosophy is very different from most other philosophies, and it takes time to understand how deep those differences really are. That's why we have membership levels here at the forum which allow for new participants to discuss and develop their own learning, but it's also why we have standards that will lead in some cases to arguments being limited, and even participants being removed, when the purposes of the community require it. Epicurean philosophy is not inherently democratic, or committed to unlimited free speech, or devoted to any other form of organization other than the pursuit of truth and happy living through pleasure as explained in the principles of Epicurean philosophy.

One way you can be assured of your time here will be productive is to tell us a little about yourself and your background in reading Epicurean texts. It would also be helpful if you could tell us how you found this forum, and any particular areas of interest that you already have.

You can also check out our Getting Started page for ideas on how to use this website.

We have found over the years that there are a number of key texts and references which most all serious students of Epicurus will want to read and evaluate for themselves. Those include the following.

"Epicurus and His Philosophy" by Norman DeWitt

The Biography of Epicurus by Diogenes Laertius. This includes the surviving letters of Epicurus, including those to Herodotus, Pythocles, and Menoeceus.

"On The Nature of Things" - by Lucretius (a poetic abridgement of Epicurus' "On Nature"

"Epicurus on Pleasure" - By Boris Nikolsky

The chapters on Epicurus in Gosling and Taylor's "The Greeks On Pleasure."

Cicero's "On Ends" - Torquatus Section

Cicero's "On The Nature of the Gods" - Velleius Section

The Inscription of Diogenes of Oinoanda - Martin Ferguson Smith translation

A Few Days In Athens" - Frances Wright

Lucian Core Texts on Epicurus: (1) Alexander the Oracle-Monger, (2) Hermotimus

Philodemus "On Methods of Inference" (De Lacy version, including his appendix on relationship of Epicurean canon to Aristotle and other Greeks)

"The Greeks on Pleasure" -Gosling & Taylor Sections on Epicurus, especially the section on katastematic and kinetic pleasure which explains why ultimately this distinction was not of great significance to Epicurus.

It is by no means essential or required that you have read these texts before participating in the forum, but your understanding of Epicurus will be much enhanced the more of these you have read. Feel free to join in on one or more of our conversation threads under various topics found throughout the forum, where you can to ask questions or to add in any of your insights as you study the Epicurean philosophy.

And time has also indicated to us that if you can find the time to read one book which will best explain classical Epicurean philosophy, as opposed to most modern "eclectic" interpretations of Epicurus, that book is Norman DeWitt's Epicurus And His Philosophy.

(If you have any questions regarding the usage of the forum or finding info, please post any questions in this thread).

Welcome to the forum!

Thanks Joshua I will incorporate that!

Quote from DaveT

My thinking was that a scholarly debate read in an academic journal, might raise the misstated issues by Pigliucci to professionals in the field. Any one of those who may better understand Epicurus though your forceful review of Pigliucci becomes a force multiplier so to speak toward your goal of clearing up misconceptions of Epicurean foundations.

Unfortunately my experience tells me to expect just the opposite as to who the "professionals in the field" can be expected to say is misguided. Although I am no Academic myself, it's my observation that Pigliucci's position is in fact the majority position of the vast majority of philosphic professionals.

This feeds back into our earlier discussion of "experts" and when to defer to them. I have to go with my reading of the sources and the commentators as to what makes sense to me after reviewing the best material available.

I'll be pleased if there are any Academics who would weigh in to agree with my position, but I don't expect it. If there were such writers out there already, we wouldn't be almost alone in the positions that have been taken on this forum on the best interpretation of Epicurus, and Pigliucci's positions would not be so prevalent.

This is an ongoing journey, and no one here should be under the false impression that they can refute Pigliucci's position by numbers of testimonials. For the present at least, anyone whose priority is to be in the mainstream of Academic scholarship likely isn't going to feel at home at EpicureanFriends.com.

Quote from DaveT

I wish you and he could engage in a scholarly journal on issues he asserted and your response.

It's an interesting question. I am not opposed to doing that at some point, and in fact I expect to do more interviews/discussions as we've done on the podcast in the past, but I need to think through exactly if and when debating with someone committed to an opposing position is worth the time.

If I were promoting myself as a guru or writing a book I wanted to sell or wanted to become a "personality" then that would clearly be the thing to do. However that is not my goal: my goal is the successful restoration of an Epicurean "camp" (to use that terminology here), and that isn't necessarily best accomplished by engaging in personality debates or trying to build my own personal "brand." I don't admit that anything we do here is anything other than correct Epicurean philosophy, so it would only detract to allow it to appear to be a "Cassius Amicus" innovation.

in fact I am remembering lately what Francis Wright had to say in A Few Days In Athens about how in-person arguments rarely produce anything good as a result.

As Martin and I and others observed over at Facebook, there is an unlimited supply of Stoics who love nothing better than arguing about detailed points of logic. The truth is that basic issues of the nature of the universe and our perspective on this world as sufficient for us, rather than focusing on a transcendent "true world" need no sophisticated analysis. The respective positions are unbridgeable and the main question is how to get the world to people who are open to the Epicurean side.

As you yourself indicated in an earlier post, engaging in debates where we have no reasonable expectations of coming to agreement with the other side. For the present I am thinking that the best thing i can do for the project is to continue to focus on the podcast and producing new content of our own. So I'm still thinking but those are my current thoughts.

We have a lot of projects going on here and those will probably continue to be my primary focus.

Quote from Don

I see you don't allow comments on Substack.

I may change that but have not thought it through.

Thank you Tau Phi.

Many of our EpicureanFriends participants arrived here after traveling through Stoicism - myself included. Many open-minded people read the Stoic materials and it's probably a good means of exposure for us to at least occasionally engage at appropriate times.

I have avoided skirmishing with the committed Stoics in the past, but I think we need at least a couple of articles setting out the ultimate points for those who are new to the study. The articles that are specifically anti-Epicurean and relatively high-profile - such as this one by Pigliucci on Substack - probably deserve individual attention.

In the future where specifically anti-Epicurean articles appear, i want to at least consider publishing a public response. I try to monitor the internet for new articles, but this one got past me for almost a month. As people see articles that deserve attention I will appreciate it if they will let me know by public thread or private message.