Posts by Cassius

Martin what is the understanding of gravity today?

Is it held to exist independently as its own entity separate from all other things?

Is gravity itself "uncaused"?

Given that it appears to take a moon-sized or planet-sized body to generate much gravity, I am still thinking that it is something that is associated with "matter" even today (?)

Edit: Do you agree with this from Grok?

Does an atom generate gravity?

Yes, a single atom generates gravity. According to both Newtonian gravity and Einstein’s General Relativity (our best current theory), any object with mass (or energy) produces a gravitational field and curves spacetime. An atom has mass—mostly from its protons and neutrons in the nucleus, plus a tiny contribution from electrons and binding energies—so it sources gravity just like a planet or star does, only vastly weaker.

I'll talk to the others and look into that. Thanks

Good thoughts Bryan. I would not want to use a word not closely related to something actually used.

Do you have any thoughts on the Greek or Latin words used in any of the places you have seen this discussed? I don't gather that "weight" is a direct transliteration of either Greek or Latin.

I see βαρύς (barys), meaning heavy, but that goes to barometer or "barium" rather than our english word.
And I see Lucretius uses both pondus which gives us "ponderous," "pound," and related English words and also gravis (heavy)

Is it as Eikadistes quoted earlier perhaps better to use the term gravity if Lucretius is using gravitas? Did the Greeks have separate word for "gravitas"?

In english gravity to me implies a force, which is really more what we are looking for.

i am finding no academic articles, but I see citation to the following place (On Fate 24) where Cicero apparently used BOTH pondus and gravitas in the same sentence, arguably implying that he considered them to be separate things (perhaps having weight BECAUSE of the gravitational force within it):

Cicero, De Fato 11.23–24

De Fato 23: "si semper atomus gravitate ferretur naturali ac necessaria" — "if the atom were always carried along by natural and necessary gravitas"

De Fato 24 (repeated): "per inane moveatur gravitate et pondere" — "moved through the void by gravitas and pondus" — and then immediately: "ipsius individui hanc esse naturam, ut pondere et gravitate moveatur" — "it is the nature of the atom itself to be moved by pondus and gravitas"

[23] Hanc Epicurus rationem induxit ob eam rem, quod veritus est, ne, si semper atomus gravitate ferretur naturali ac necessaria, nihil liberum nobis esset, cum ita moveretur animus, ut atomorum motu cogeretur. 11. Id Democritus, auctor atomorum, accipere maluit, necessitate omnia fieri, quam a corporibus individuis naturalis motus avellere. Acutius Carneades, qui docebat posse Epicureos suam causam sine hac commenticia declinatione defendere. Nam cum docerent esse posse quendam animi motum voluntarium, id fuit defendi melius quam introducere declinationem, cuius praesertim [p. 261] causam reperire non possent; quo defenso facile Chrysippo possent resistere. Cum enim concessissent motum nullum esse sine causa, non concederent omnia, quae fierent, fieri causis antecedentibus; voluntatis enim nostrae non esse causas externas et antecedentis.

24] Communi igitur consuetudine sermonis abutimur, cum ita dicimus, velle aliquid quempiam aut nolle sine causa; ita enim dicimus “sine causa”, ut dicamus: sine externa et antecedente causa, non sine aliqua; ut, cum vas inane dicimus, non ita loquimur, ut physici, quibus inane esse nihil placet, sed ita, ut verbi causa sine aqua, sine vino, sine oleo vas esse dicamus, sic, cum sine causa animum dicimus moveri, sine antecedente et externa causa moveri, non omnino sine causa dicimus. De ipsa atomo dici potest, cum per inane moveatur gravitate et pondere, sine causa moveri, quia nulla causa accedat extrinsecus.

M. Tullius Cicero, De Fato, section 24

And solving the problem of terminology doesn't require that we wait for some kind of explicit physics rechnology explanation, any more than Epicurus waiting before taking about uncuttable atoms or the swerve. The issue is that the atoms possess within themselves the power of movement and don't wait on gods or outside forces of any kind to bestow it on them.

The sole external requirement is space to move within.

"Weight" carries modern connotations that obscure that original intent of independent capacity, and also makes it harder to see how the swerve is equally uncaused.

Yes I presume Goodwin is struggling with the same issue we are discussing. Epicurus is apparently using the word to designate a capacity for self-generated motion (as in the swerve) and in English "weight" does not give us that self-moving capacity. We need to figure out how to convey this better.

Aenaedum tells us:

I have an undergraduate degree in Classics, with a focus on Horace and Lucretius, and a Masters in Comp Lit, with work on Montaigne and ataraxia. I've self-identified as a follower of Epicurus for many years, so I'm interested to learn more about how his philosophy can be applied in current day settings. From a practical standpoint, I intend to use what I learn to help people I sponsor in a 12 step program to find guidance from Epicurus in their recovery and everyday life.

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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!

Note - I moved posts from wbernys and eikadistes to the subforum for PD06 as they are very useful there and can be found there more easily in the future.

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.

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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.

X.

Zeno, then, was not at all a man like Theophrastus, to cut through the sinews of virtue; but, on the other hand, he was one who placed everything which could have any effect in producing a happy life in virtue alone, and who reckoned nothing else a good at all, and who called that honourable which was single in its nature, and the sole and only good. But as for all other things, although they were neither good nor bad, he divided them, calling some according to, and others contrary to nature. There were others which he looked upon as placed between these two classes, and which he called intermediate. Those which were according to nature, he taught his disciples, deserved to be taken, and to be considered worthy of a certain esteem. To those which were contrary to nature, he assigned a contrary character; and those of the intermediate class he left as neutrals, and attributed to them no importance whatever. But of those which he said ought to be taken, he considered some worthy of a higher estimation and others of a less. Those which were worthy of a higher esteem, he called preferred; those which were only worthy of a lower degree, he called rejected. And as he had altered all these things, not so much in fact as in name, so too he defined some actions as intermediate, lying between good deeds and sins, between duty and a violation of duty; — classing things done rightly as good actions, and things done wrongly (that is to say, sins) as bad actions. And several duties, whether discharged or neglected, he considered of an intermediate character, as I have already said. And whereas his predecessors had not placed every virtue in reason, but had said that some virtues were perfected by nature, or by habit, he placed them all in reason; and while they thought that those kinds of virtues which I have mentioned above could be separated, he asserted that that could not be done in any manner, and affirmed that not only the practice of virtue (which was the doctrine of his predecessors), but the very disposition to it, was intrinsically beautiful; and that virtue could not possibly be present to any one without his continually practising it.

And while they did not entirely remove all perturbation of mind from man, (for they admitted that man did by nature grieve, and desire, and fear, and become elated by joy,) but only contracted it, and reduced it to narrow bounds; he maintained that the wise man was wholly free from all these diseases as they might be called. And as the ancients said that those perturbations were natural, and devoid of reason, and placed desire in one part of the mind and reason in another, he did not agree with them either; for he thought that all perturbations were voluntary, and were admitted by the judgment of the opinion, and that a certain unrestrained intemperance was the mother of all of them. And this is nearly what he laid down about morals.

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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....