Posts by Cassius

Good thoughts as to the correspondence, Eikadistes. I haven't got much to go on yet but I think there's a bright line and that Epicurus would require that "weight" not imply that this particular cause of the motion of atoms is operating only because of some external force separate from matter and void. (In other words, given that the universe is infinite in size in all directiions and there's no "bottom," there's no force outside the atoms pulling them "down."

Regardless of anything else, our notion of gravity implies something giving off an attractive force at a distance. Maybe there's something in the magnetism discussion in Lucretius that could be used to explain what "weight" might mean without requiring "action at distance" (without touch being involved).

Thanks Joshua. So clearly the word being used is "weight." It seems possible however that that does not end the inquiry because it's potentially not clear what is meant by weight.

Today (i gather) we are using weight as something that is attracted differentially by gravity (?)

Epicurus apparently was not using that paradigm (and would not, given that what we think of gravity would be a force outside the atom) ??

What Seldey seems to be saying is that Epicurus is using the term to mean a potential to move when space allows it, which itself is the cause of motion without interaction with anything outside it.

Am I reading that right? If so then a straight use of "weight" in our modern context might be confusing the issue just as it is confusing to think that Epicurus meant "atom" in the same way we do.

In a nearby thread we have discussed the analysis of space travel from the Epicurean point of view (Would Epicurus embrace going to the moon).

That's a very good specific example and might be all that's needed, but I am setting this thread up as a place to unify other examples of how to analyze risks vs reward and state the Epicurean attitude toward risk aversion more directly.

So to discuss the general issue of risk aversion outside of the specific space travel hypothetical, please post in this thread.

Post

RE: What would Epicurus have thought of going to the moon?

One thing I'd add is that if we go by the list in the principal doctrines , only the concept of there being no supernatural gods comes before the doctrine that "you only live once." (And even the absence of supernatural gods is directly related to living only once and for a short period.)

In my first answer I focused on everyone having different personal tastes and preferences in life. We have a limited amount of time to pursue what we find to be most pleasurable, and I don't see how it makes…

Cassius

April 12, 2026 at 6:06 AM

So the reason this topic came up today is that Patrikios brought up the question of whether atoms move because of some external force applied to them. And this directly relates to the motion of bodies such as magnets, discussed in Book 6 of Lucretius.

If I am reading this correctly, then it would not be appropriate to say that the the three eternal properties of atoms are size, shape, and motion. It is correct to say "size, shape, and weight."

However Epicurus intended "weight" to be understood as the internal cause of motion without need of any external force (which we might think of as gravity) acting on it. Thus Epicurus was holding that no external force is required to cause atoms to move, as they have moved eternally.

If someone has a better way to state that please post.

The Routledge Encyclopedia entry by David Sedley

4. Motion

Surprisingly, atoms never stop moving, even within a compound object, since the medium through which they move is void, which can offer them no resistance. More surprisingly, for the same reason they move at a vastly greater speed than any familiar motion through an obstructive medium such as air; even than sunlight, which is seen to spread from horizon to horizon virtually instantaneously (Lucretius II 142–64). More surprisingly still, they all move at equal speed, since in a vacuum, unlike air, there is no resistance from the medium to slow down the lighter ones more than the heavier ones (Letter to Herodotus 61). In stating all these claims, Epicurus is accepting paradoxical consequences of the hypothesis that void exists, consequences which Aristotle had drawn (Physics IV) in the belief that they were sufficiently absurd to discredit the hypothesis. Moreover, the equal speed of atoms was confirmed by another objection Aristotle thought he had found to atomism (Physics VI 2): if there is a minimal magnitude, there can be no differences of speed, because then in the time the faster object took to travel one minimum the slower one would, impossibly, have to travel less than one minimum. Epicurus welcomed this argument, along with the conclusion Aristotle thought absurd, because his theories of void and minima now offered two independent grounds for the same conclusion, that atoms move at equal speed.

The apparent lack of fit between these findings about atoms and the variable speed of macroscopic motions is explained as follows (Letter to Herodotus 62). Even in a compound object the individual atoms are perpetually moving, but in tight and regular cyclical patterns which make the complex as a whole stable. Phenomenal differences of speed, say between two runners, represent merely the aggregate motions of the atoms in each over an observed period of time.

There are three causes of an atom’s motion. The first is its own weight, interpreted as an inherent tendency to move downwards (see §8). The second is collisions with other atoms, which can deflect an originally downward motion along any number of new rectilinear trajectories, thus generating the patterns of motion of which compounds are born.

The third cause of atomic motion is the ‘swerve’ (parenklisis), whereby an atom may shift from its rectilinear trajectory onto an adjacent one – a displacement sideways by a distance of one minimum (there being no smaller distance). This happens ‘at no fixed place or time’, meaning that the occurrence of a swerve is causally undetermined. The theory, derided by Epicurus’ opponents but now recognized as comparable in its implications to modern quantum indeterminism, looks like a drastic solution requiring a drastic problem. Two such problems are recorded (Lucretius II 216–93). First, since all atomic motion starts out as vertical and equal in speed, without a swerve no collisions would ever have started, and hence no world could have been formed. It may be doubted whether this was a sufficiently pressing problem to motivate an abandonment of universal causality: given the infinite past history of the universe,Epicurus had no need to posit a very first collision; in which case every collision could have been explained as the effect of previous ones. The second problem seems to have been the real motivation of the swerve: if all atomic motion is causally determined, free will becomes impossible (see §12).

https://www.rep.routledge.com/articles/thematic/epicureanism/v-1/sections/motion

Ok I asked Claude to summarize David Sedley's position. Apparently the main article is not publicly available but I will include the cite below:

The key Sedley text regarding the Epicurean relationship between weight and motion turns out to be his own entry in the Routledge Encyclopedia of Philosophy (1998), where he lays this out with unusual precision. Here is what he says:

Weight as the first of three causes of motion

There are three causes of an atom's motion. The first is its own weight, interpreted as an inherent tendency to move downwards. The second is collisions with other atoms, which can deflect an originally downward motion along any number of new rectilinear trajectories, thus generating the patterns of motion of which compounds are born. The third cause of atomic motion is the swerve, whereby an atom may shift from its rectilinear trajectory onto an adjacent one — a displacement sideways by a distance of one minimum. Routledge

So Sedley's answer is precise and structural: weight is not merely a property atoms happen to have — it is the first cause of motion itself. It is the explanatory ground of atomic movement before anything else enters the picture.

Weight does not control speed

Then comes the crucial complication Sedley also states directly: atoms all move at equal speed, since in a vacuum, unlike air, there is no resistance from the medium to slow down the lighter ones more than the heavier ones. Routledge This is Sedley citing Letter to Herodotus 61. So weight is the cause of motion but plays no role whatsoever in determining how fast atoms move — all atoms move equally fast regardless of their weight or size.

The implication

Taken together, Sedley's position gives you the clearest possible statement of why "weight" in Epicurean physics is so philosophically strange. Weight is the source of motion — the intrinsic directional tendency that makes atoms move at all — but it does not differentiate fall-rate, does not produce attraction between atoms, and does not operate the way ordinary physical weight does. The atom's property of weight was designed to account for motion as a whole in Epicurus' physics St-andrews — it is the answer to Aristotle's objection that Democritus had no explanation for why atoms move in the first place.

This is exactly why "motion" seems like it could substitute for "weight" — because in Sedley's reading, Epicurean weight just is the cause of natural motion, and the two concepts are inseparable. But Sedley himself maintains "weight" as the right term because the Greek is clearly βάρος, and because weight is the cause of motion, not motion itself. Substituting "motion" would collapse the distinction between the property and what the property produces — which matters for understanding how the swerve then modifies things.

This topic arose in today's Zoom meeting and it needs further research and expansion. I am also going to modify the title of this thread to make the issue more clear.

I feel sure there are academic articles directly on point beyond what I've cited above.

One thing I'd add is that if we go by the list in the principal doctrines, only the concept of there being no supernatural gods comes before the doctrine that "you only live once." (And even the absence of supernatural gods is directly related to living only once and for a short period.)

In my first answer I focused on everyone having different personal tastes and preferences in life. We have a limited amount of time to pursue what we find to be most pleasurable, and I don't see how it makes sense to do anything other than pursue our greatest pleasures in as intelligent a manner as we can.

All that is to say that some people doubtless have zero interest in flying into space. If they have no desire to do that and find no pleasure in it, then of course they won't choose to do so. Far be it for me to tell them that they are wrong about their feelings - everyone has to make those decisions for themselves.

But for me, and I see this compelled by life is short and then it's over, I am drawn to the conclusion that I need to use my time as productively as possible to do things that bring me the greatest pleasure. For me, "tranquility" in the sense of detachment from all emotion -- which is what some people seem to think that "absence of pain" means - is not my goal.

To me, writers who focus on talking about "absence of pain" do not see that Epicurus was using that term as the exact equivalent of the word "pleasure." They are ignoring the very logical reasons why he did so, and the very detailed explanation of those reasons found in Cicero and Diogenes Laertius.

So philosophically I think Epicurus would say people who think going into space would bring them pleasure than pain under their own circumstances should do it. Those who think it would bring more pain to them than pleasure should not do it.

But in my own case I apply that rule this way: I know that knowledge and new experiences are not necessarily pleasurable in themselves. It makes no sense to pursue knowledge or experiences which do not lead to greater pleasure. But if I could do so safely -- and at some point that will be possible - I can think of few if any experiences that would bring more pleasure than space travel.

These week we will continue around section 1:329 of Lucretius and explore the implications of the Void.

EpicureanFriends Side-By-Side Lucretius

Multi-column side-by-side Lucretius text comparison tool featuring Munro, Bailey, Dunster, and Condensed editions.

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Welcome to Episode 329 of Lucretius Today. This is a podcast dedicated to the poet Lucretius, who wrote "On The Nature of Things," the most complete presentation of Epicurean philosophy left to us from the ancient world. Each week we walk you through the Epicurean texts, and we discuss how Epicurean philosophy can apply to you today. If you find the Epicurean worldview attractive, we invite you to join us in the study of Epicurus at EpicureanFriends.com, where we discuss this and all of our podcast episodes.
   
This week we start are continuing our series reviewing Cicero's "Academic Questions" from an Epicurean perspective. We are focusing first on what is referred to as Book One, which provides an overview of the issues that split Plato's Academy and gives us an overview of the philosophical issues being dealt with at the time of Epicurus. This week will focus on the ending of Section 9.

Our text will come from
Cicero - Academic Questions - Yonge We'll likely stick with Yonge primarily, but we'll also refer to the Rackam translation here:

• Cicero On Nature Of Gods Academica Loeb Rackham : Free Download, Borrow, and Streaming : Internet Archive

Quote from Academic Questions - Yonge

IX.

This was the first philosophy handed down to them by Plato. And if you like I will explain to you those discussions which have originated in it.

Indeed, said I, we shall be glad if you will; and I can answer for Atticus as well as for myself.

You are quite right, said he; for the doctrine both of the Peripatetics and of the old Academy is most admirably explained.

Aristotle, then, was the first to undermine the doctrine of species (forms), which I have just now mentioned, and which Plato had embraced in a wonderful manner; so that he even affirmed that there was something divine in it. But Theophrastus, a man of very delightful eloquence, and of such purity of morals that his probity and integrity were notorious to all men, broke down more vigorously still the authority of the old school; for he stripped virtue of its beauty, and made it powerless, by denying that to live happily depended solely on it. For Strato, his pupil, although a man of brilliant abilities, must still be excluded entirely from that school; for, having deserted that most indispensable part of philosophy which is placed in virtue and morals, and having devoted himself wholly to the investigation of nature, he by that very conduct departs as widely as possible from his companions.

But Speusippus and Xenocrates, who were the earliest supporters of the system and authority of Plato,— and, after them, Polemo and Crates, and at the same time Crantor,— being all collected together in the Academy, diligently maintained those doctrines which they had received from their predecessors. Zeno and Arcesilas had been diligent attenders on Polemo; but Zeno, who preceded Arcesilas in point of time, and argued with more subtilty, and was a man of the greatest acuteness, attempted to correct the system of that school. And, if you like, I will explain to you the way in which he set about that correction, as Antiochus used to explain it. Indeed, said I, I shall be very glad to hear you do so; and you see that Pomponius intimates the same wish.

OK other than Eikadistes no one is rushing to answer, so I'll start a preliminary response that will be far too short.

Quote from ReiWolfWoman

What do you think Epicurus would have thought of going to the moon? Would it be extraneous to friendship and community and pleasure, and therefore a search for an unnecessary (and natural or unnatural) goal? Or would he see it as a search for connection, expanding community, and a necessary pleasure of some kind for either an individual or their community?

As with all options in life, I think Epicurus would advise evaluating the specifics as it applied to him personally and not take things too abstractly.

"Going to the moon" could mean the 1969 version where the technology is in its infancy and you're very strongly taking your life in your hands with major possibility of death and not coming home. Or it could mean a 2050 version where the trip may well be routine and doable in great safety and of no more concern than a short vacation to the mountains.

Then there's the "who." Are we talking about an Epicurus at 30 years old who was in the course of building philosophical school who he thought was of extreme importance not only to himself but to others? Or are we talking about a 70 year old Epicurus with most of his life's work behind him and much less time to lose if he didn't make it back?

Those are two specific circumstances I think he would advise considering -- but I suspect that's not the answer many people with conventional views of Epicurus will expect.

They'll expect "Epicurus valued bodily pleasure and safety and tranqulity above all, and it's certainly not NECESSARY to go to the moon, nor is it likely to be a totally tranquil experience, so he'd never do it. You're totally ignoring what everyone says about Epicurean philosophy to say that he'd ever consider it under any circumstances!"

That's not the answer I'd give ReiWolfWoman, and I hazard to guess that most others here would not say that either.

And thus you've early in your time at EpicureanFriends.com discovered that this forum was not set up to support conventional views of Epicurus that place in him boxes like "tranquility above all."

And not only was it not set up to support such views, it's pretty fair to say that it was set up to campaign against them as vigorously as possible.

And the more you look around here at the forum and see the discussions, the more I think you'll see what that is!

Thanks Patrikios that is a very new document that I am still in the process of researching and revising, but it's already very helpful. I will add that as you suggest.

EDIT: HMMM how did you get that link - it's not correct - I will get the correct one and update your post....

Quote from Kalosyni

I think that the Epicurean needs to spend time contemplating the truth of the cessation of the senses and the mind. And, also needs to focus intently on living life to the fullest by making good and joyful choices - and in a way "make heaven on earth".

And the best way to do that is through regular teamwork with people who already agree or are close to agreeing with you, and not continuing to imagine that maybe the rest of the world will one day wake up and everything will be different.

If someone studying Epicurus is stuck doing so by themselves, and making no further changes with the people they associate with, then they might as well just put the book back on the shelf for all the good it will do them.

And sitting around waiting for an Epicurean "commune" to open up across town is equally unrealistic and unproductive.

Thank you for highlighting that quote wbernsys - I missed it when I first read the post.

Since those two terms seem to be of interest i would appreciate m.dangoexplaining briefly what those terms mean and why they come up here so as to make the thread most useful for other readers.

This is a fine place for this question and thank you for posting it. i may designate it so it appears in an Ehics section as well.

I expect some highly perceptive answers, and I think the issue is important enough that I don't want anyone to hold back what they really think regardless of what anyone else who posts in this thread says.

And it might help too if those who post consider the question in terms of both (1) What would Epicurus himself have thought? and (2) What do I (the poster) think?

Further, I hope the responses won't limit themselves to "the moon" and thereby short-circuit the heart of the question. I doubt ReiWolfWoman is trying to parse the difference between going to the Moon vs going to Mars vs the entire topic of space exploration.

Should be an interesting discussion.

Thanks Bryan - it's a shame that we do focus on the term "atom" as if he were concerned about a particular object, when what he really was concerned about the logical imperative that there must be a limit to a division of both bodies and space!

It's so much easier for people to dismiss him by putting him in a box labeled "atoms" than to realize that what he's really campaigning against is the use of logic divorced from sensation to overthrow the senses.

Episode 329 of the Lucretius Today Podcast is now available. This week our episode is entitled: "Sensation - While Neither Right Or Wrong - As The Touchstone Of Reality"

There are several major omissions in the existing list and I will eventually revise it. In the meantime and while I think about the existing structure and consider any incoming comments, here are four more that I am going to add:

26. A life that does not last forever is not worth living.

Epicurus cures this by showing that the length of a life and the quality of a life are two entirely different things. As he states directly in the Principal Doctrines, "Infinite time contains no greater pleasure than limited time, if one measures by reason the limits of pleasure." The pleasure of a good meal is complete when hunger is satisfied; the pleasure of a deep friendship is complete in the living of it; neither of these is improved by being repeated forever. The demand for immortality as a condition of a meaningful life is therefore a confusion — it mistakes duration for value and treats the good life as something that can only be justified if it never ends, which is precisely the kind of thinking that prevents people from fully inhabiting and appreciating the life they actually have.

27. No matter how much pleasure I have, I always need more to stay satisfied.

Epicurus cures this by drawing a precise and liberating distinction between the removal of pain — which is the actual goal — and the endless addition of more stimulation on top of it. He states in the Principal Doctrines that "the limit of quantity in pleasures is the removal of all that is painful," and further that once the pain of want is removed, pleasure is not increased by adding more — it is only varied. Once hunger is fully satisfied, you are not in a state that requires ever-larger meals to maintain your happiness; you are already at the natural limit of that pleasure. This matters enormously because the belief that pleasure is always deficient and always demands more to sustain it is the very engine of insatiable desire — the endless pursuit of wealth, novelty, and stimulation that Epicurus identified as one of the chief sources of human misery.

28. The pains of life will always make it impossible to be happy.

Epicurus cures this by showing first that happiness is not a moment-by-moment condition but a property of a whole life, and second that a whole life well-lived is fully capable of including pain without being destroyed by it. The question is never whether any particular day is free from suffering, but whether your life as a whole — looked at honestly from beginning to end — contains more pleasure than pain, and whether you are able to appreciate and enjoy that life as the complete thing it is. Just as a good day is not ruined by a difficult hour, a good life is not cancelled by periods of pain, and the mind has a remarkable capacity to draw on the entire span of one's experience — on the memory of past pleasures, on the pleasures of friendship and reflection available right now, and on the confidence that what lies ahead holds no terrors — in a way that can outweigh even serious physical suffering. In the Principal Doctrines Epicurus states that extreme pain tends to be brief, and that pain which does persist over time does not typically hold its most intense levels for long. More importantly, Epicurus himself demonstrated the whole argument at his own death: writing in his final hours while in severe physical pain, he reported that the joy he felt in remembering his philosophical conversations with friends set itself against all of it. He was not claiming to feel no pain. He was showing that a life rich enough in genuine pleasure — built over years through friendship, thought, and the practice of living well — carries resources that physical suffering alone cannot take away.

29. Justice is absolute — the same rules should apply to everyone, everywhere, at all times.

Epicurus cures this by showing that justice is not a set of eternal rules handed down by a god from above but something that real people create for themselves through agreements made under specific circumstances. In the Principal Doctrines he states plainly that Justice as a single thing in itself does not exist in nature. What exists are agreements among people in particular places and times about how to avoid harming one another for their mutual benefit. This means that what counts as just can and does change as circumstances change: an agreement that served mutual protection under one set of conditions may need to be revised or replaced when those conditions shift, and clinging to old arrangements simply because they once worked is not justice but rigidity. The demand for a single, timeless, universal standard of justice — whether grounded in divine law, abstract reason, or natural right — is itself a source of harm, because it blinds people to the actual human purpose that justice serves and makes it harder to adapt agreements to the real conditions of real communities.

For reference as to the term mind virus

Viruses of the Mind - Wikipedia

This thread will be used for discussion of the new beginner-friendly article: Mind Viruses Cured By Epicurean Philosophy. Please add comments, suggestions, etc. here.

Article

25 Mind Viruses Cured By Epicurean Philosophy

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Throughout history, philosophers, priests, and political authorities have promoted ideas about life, reality, and human nature that sound profound but are in fact deeply mistaken — and whose effect, whether intended or not, is to make ordinary people feel guilty, fearful, and dependent on outside authorities for guidance. These ideas spread from generation to generation the way a virus spreads through a population: not because they are true, but because they are…

Cassius

April 10, 2026 at 11:39 AM