Episode 129 - Letter to Pythocles 03 - The Implications Of the Epicurean Position On The Size of the Sun
Date: 07/09/22
Link: https://www.epicureanfriends.com/thread/2585-episode-one-hundred-twenty-nine-letter-to-pythocles-03-the-implications-of-the-e/
Summary
Section titled “Summary”Joshua reads section 91 of the Letter to Pythocles, which states that the size of the sun, moon, and stars is “what it appears to be — either slightly greater than what we see, or slightly less, or the same size”; the central discussion is organized around T.H.M. Geller Goade’s essay “Lucretius and the Size of the Sun” in Epicurus in Rome: Philosophical Perspectives in the Ciceronian Age (February 2022), which argues that Cicero’s mockery — that Epicurus thought the sun was a foot in diameter — misrepresents a principled epistemological position. The core argument runs from Lucretius Book 5 lines 564-585 (fires do not visibly shrink with distance the way solid objects do) and the tower problem (a tower looks round from afar but square up close) to the observation that the sun, unlike a tower, cannot be approached to establish a changing scale — making “the size as it appears” not a naive claim but an honest acknowledgment of the limits of unaided observation. Joshua develops Geller Goade’s shibboleth thesis: Epicurus used this formulation as both an epistemological teaching device and a deliberately safe way to challenge astronomical orthodoxy — Anaxagoras had been condemned to death in Athens for saying the sun was a mass of blazing metal larger than the Peloponnese and escaped only by fleeing to Lampsacus, while Giordano Bruno was burned in the Campo dei Fiori by the church centuries later for similar views. The measurement discussion broadens into an exchange on historical and modern standards: Martin gives the cesium-133/speed-of-light definition of the meter (speed of light defined as 299,792,458 m/s; second as 9,192,631,770 periods of the cesium-133 ground-state transition; meter as the path light travels in 1/299,792,458 of a second); Joshua covers Thomas Jefferson’s proposal to define the foot as the length of a one-second pendulum; Cassius raises the klepsydra water clock used for equal speaking time in Athenian courts and Isaac Newton’s role at the Royal Mint in etching ridges on coins to prevent clipping. The episode closes by connecting physics and ethics: just as measurement must be grounded in reproducible observation traceable through a chain of standards, the Epicurean canon of truth is a measuring rule (kanon = straight edge or ruler), not a list of arbitrary decrees, and the ultimate standard in ethics is the felt experience of pleasure and pain — both illustrate that validity comes only from what can be personally observed and verified.
Transcript
Section titled “Transcript”Cassius: Welcome to Episode 129 of Lucretius Today. This is a podcast dedicated to the poet Lucretius, who wrote On the Nature of Things, the only complete presentation of Epicurean philosophy left to us from the ancient world. I’m your host Cassius, and together with our panelists from the EpicureanFriends.com Forum, we’ll walk you through the ancient Epicurean texts and discuss how Epicurean philosophy can apply to you today. We encourage you to study Epicurus for yourself, and we suggest the best place to start is the book Epicurus and His Philosophy by Canadian professor Norman DeWitt. If you find the Epicurean worldview attractive, we invite you to join us in the study of Epicurus at EpicureanFriends.com, where you’ll find a discussion thread for each of our podcast episodes and many other topics. Today we continue in Epicurus’s Letter to Pythocles, and we look at the implications of the Epicurean position on the size of the sun. Now let’s join Joshua reading today’s text.
Joshua: The size of the sun and moon and the other stars is for us what it appears to be. And in reality, it is either slightly greater than what we see, or slightly less, or the same size. For so too fires on earth, when looked at from a distance, seem to the senses. And every objection at this point will easily be dissipated if we pay attention to the clear vision as I show in my books about nature. The risings and settings of the sun, moon, and other heavenly bodies may be due to kindling and extinction, the composition of the surrounding matter at the places of rising and setting being such as to lead to these results, for nothing in phenomena is against it. Or again the effect in question might be produced by their appearance over the top of the earth, and again the interposition of the earth in front of them, for once more nothing in phenomena is against it. Their motions may not impossibly be due to the revolution of the whole heaven, or else it may remain stationary and they may revolve owing to the natural impulse towards the east, which was produced at the beginning of the world by an excess of heat owing to a spreading of the fire, which is always moving on to the regions nearest in succession. The tropics of sun and moon may be caused owing to an obliquity of the whole heaven which is constrained into this position in the successive seasons, or equally well by an outward emission of a current of air, or because the appropriate material successively catches fire as the former fails; or again from the beginning this particular form of revolution may have been assigned to these stars so that they move in a kind of spiral. For all these and kindred explanations are not at variance with any clear-seen facts, if one always clings in such departments of inquiry to the possible and can refer each point to what is in agreement with phenomena without fearing the slavish artifices of the astronomers.
Cassius: Thank you, Joshua. We welcome you back — you’ve been reading starting around section 91. Last week we took a break and talked about the Twelve Fundamentals, and now we’re back to where we were two weeks ago on the issue of the size of the sun and other astronomical phenomena. Today’s focus covers several aspects of the sun and the moon and the other heavenly bodies, but the one I think we want to spend the most time on is probably one of the more famous — and controversial — observations Epicurus made in the ancient world: the size of the sun. It’s frequently stated that Epicurus thought the sun was about the size of our foot, or as we might say today, about the size of a basketball. I think there is a lot more to the story than that, which we will go into today. He doesn’t just assert that the size of the sun is as it appears to be — he gives reasons for that observation. So welcome back, Joshua. Any place you’d like to start?
Joshua: Thank you — it’s good to be back. I missed two weeks but now I’m back to the normal schedule. You’re absolutely right to say this is one of the more intriguing claims Epicurus makes, and certainly one of the more controversial. You would think that his claim that pleasure is the end of life would be more controversial, but in fact what we often see in argumentation is this: the main point might be argued with, but as soon as the person you’re arguing against makes a misstep or speaks wrongly about one thing, there’s a tendency to cling to that one thing — as if arguing about it is going to bring down the whole system.
This argument that Epicurus thought the sun was about a foot in length comes down to us from Cicero, who had every interest in thinking Epicurus was totally wrong. Now this is our total focus, and it will be important to keep in mind a particular essay published fairly recently — it appeared in February of this year, 2022 — in a collection called Epicurus in Rome: Philosophical Perspectives in the Ciceronian Age. The article is by an academic named T.H.M. Geller Goade: “Lucretius and the Size of the Sun.” Cicero is very much at the heart of the conversation here. What we need to determine today, Cassius and Martin, is whether Cicero’s interpretation of Epicurus on this passage is completely wrong.
Cassius: As we begin to dig in, what’s stated in section 91 is not just the bare assertion that the sun is as it appears to be — as usual Epicurus includes at least a little of his reasoning. We can also refer to Lucretius Book 5 starting around line 564 for a more extended discussion. But first, it’s worth pointing out that he doesn’t just take the position that the size of the sun is as it appears — he gives reasons for that observation. In this section he says: “For so too fires on earth, when looked at from a distance, seem to the senses.” That issue is developed significantly further in Lucretius. At line 564 he says: “For from whatsoever distances fires can throw us their light and bring their warm heat upon our limbs, they lose nothing of the body of their flames because of the interspaces. Their fire is no whit shrunken to the sight.” So there is something Epicurus is observing about the way light travels over distance — light sources behave optically differently than solid objects at distance. And then at around line 585, Lucretius says: “The fires of heaven that you see from earth — in as much as all fires that we see on earth, so long as their twinkling light is clear, so long as their blaze is perceived, are seen to change their size only in some very small degree, greater or less, the further they are away.” He’s saying that observation about sources of light must be factored into our reasoning about the sun’s size. And there’s the related observation — familiar from the tower problem we’ve discussed many times — that things at a distance become less distinct. The sun and moon appear with remarkable sharpness, which is not what we observe on earth with distant solid objects. Both of those phenomena are what Epicurus is analyzing. Maybe the most important point to remember is that he’s not taking a position in miles or kilometers — his conclusion is stated not as a particular measurement but as a standard of measurement: it is what it appears to be.
Joshua: There’s actually a slight problem there too, isn’t there. When the text says “the size of the sun is for us what it appears to be” — this is a problematic distinction. You could say the same thing about a tower: the size of the tower from far away is to us what it appears to be, but when you get up close you see that the size of the tower is different from what you first thought. Here’s the major point: you have what the sun looks like to us from our position on earth, and then you have this separate thing — the absolute size of the sun, the size of the sun relative to itself. And the problem with the sun and the moon and the stars — a problem we don’t have with the tower — is that we can’t get closer to them. Epicurus in the third century BC couldn’t get any closer to the sun to determine the way we can with a tower: walk up to it and see it change scale relative to yourself. With the sun there is no other frame of reference. Our senses cannot get a hold of another angle. And it’s at that point that Epicurus starts reaching for other frames of reference — the fire observation, the clarity argument. The fundamental problem from his point of view is that the size of the sun cannot be known, because we can’t measure it and we can’t get close enough to appreciate its changing scale. We’re tethered to the earth no matter how far east or west or north or south you go — at no point do you really get close enough or far enough away to appreciably change the scale of the sun’s appearance.
And if you’re going to take the position Epicurus takes — that our senses are how we know what is true about the real world, not the astronomy or astrology of his predecessors and contemporaries — then it is simply not possible to know how big the sun is. At no point in any Epicurean text does Epicurus or any of his successors make the claim Cicero makes that the sun is a foot in diameter. So that is where we need to start: there is what the size of the sun appears to be to us, and then there is what the size of the sun is absolutely or objectively. And we can’t bridge that gap.
Cassius: Joshua, you used a word repeatedly that I think is extremely useful — “scale.” Our ultimate measurements are comparisons of one thing to another. You can go to Wikipedia and get a measurement of the sun using modern technology, but it will all be in terms of some kind of scale — miles, kilometers, whatever. But what is a mile or a kilometer? At one point I was reading that the meter was just a consensus based on a standard arbitrarily set — something in Paris, a rod of some kind. Is that correct? That a meter was just a consensus based on a standard that was arbitrarily set?
Martin: That is part of the history. They did have brass rods. The problem with metal for this rod is thermal expansion — when it gets hot, the rod gets bigger; when it gets cold, it gets smaller.
Joshua: Right now I think the meter or the kilometer has something to do with the circumference of the earth at the equator — one kilometer is one second of one minute of one degree of circumference at the equator, or something like that.
Martin: No. That is outdated. Since long it has been defined based on atomic physics. Let me find this.
Cassius: Let me give one more example here, probably also outdated by now. Thomas Jefferson came up with an idea for a metric system and proposed it to the British, and they together proposed it to the French, but they couldn’t get the French to agree to his system. Jefferson wanted to use the foot as the basis, defined as the length of a pendulum whose swing takes exactly one second. It was at that point that the French decided, no, we’re going to go measure the circumference of the earth. But Martin, you’re saying that’s outdated.
Martin: Yes. It has become more complicated since the time I started this, so let me give the current definition. The speed of light has been defined as 299,792,458 meters per second. And the definition of a second is 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. That is definitely something where you need a fairly sophisticated laboratory to reproduce this basic definition. What we do in practice is buy clocks which have been calibrated through a chain of standards back to a NIST laboratory or another laboratory which can reproduce the second based on this definition. And then the meter is defined as the length of the path traveled by electromagnetic radiation in a vacuum during a time interval of one of 299,792,458 of a second — so roughly one three-hundred-millionths of a second. Again, to measure this way you need laboratory equipment. In practice you again buy calibrated standards which come through a chain referenced back to some laboratory which can reproduce the standard based on the definition. On some satellites they may have actual atomic clocks on board that go back to this definition in real time.
Cassius: And this reminds me of a point that was new to me when I first read the DeWitt book — that the word canon, as in the Epicurean “canon of truth,” is not necessarily a list of principles but is equivalent to a ruler or straight edge, something you compare other things to. The kanon is not from Epicurus’s point of view a list of conclusions about particular subjects — it’s a discussion of the method of measuring and the method of proceeding toward a conclusion. What you’ve been talking about in terms of selecting units of measurement — the implication is that it is you who decide what unit of measure to use, whether a meter or a yard or a foot. Once you’ve selected the measure, you’ve got to apply it. Just the fact that a meter is a particular length is of not much significance on its own — the question is what it is you’re measuring.
Martin: Yes. And this is really no different than using dollars versus euros versus pounds sterling. We come up as humans with a standard of measurement that means something to us and use it for our transactions from day to day. Historically that thing would have been the human foot — but every person has a different length of foot, so if we’re building a house together and my foot is bigger than yours we’re going to have some problems.
Cassius: And why do we care so much about repeatability and reproductibility? One of the reasons is that there are people in this world who will shave the edge off a coin, who will put their thumb on the scale, who will manipulate positions to suit their own purposes even in philosophy. You want something that removes as much as possible the possibility of corruption or bias. You want something as uniform as possible to serve as your standard.
Joshua: You’re absolutely right. And what Thomas Jefferson really wanted was for commerce to be done in square volume — instead of a round wine bottle, a square bottle — so that any farmer who went into town to trade needed only a ruler to tell whether the merchant was trying to cheat him. On that subject, I think it was Isaac Newton who was given a notional post at the Royal Mint — it may have been an excuse to give him money, but he apparently took it quite seriously. It was because of him that they started putting ridges on the edge of coins. If you look at the side of a dime, for example, it has those ridges etched into it. When money was made of actual precious metal, the point was that you could tell just by looking at the side whether someone had clipped the coin, because that factory edge would be missing.
Cassius: And of course in ancient Greece they had the klepsydra — a water clock — used in the courts of law to give each side equal speaking time. You’d have this water tank with an allotment for how long you could speak. They’d pull the plug and you’d start talking. When the water ran out, you had to stop. Without short-circuiting our discussion, I really do think that’s the direction we’re going in here. The lesson to be taken from all this is that whatever size the sun is, you get it by observing it through your senses — the appearances. The word “appearance” can have negative connotations, as if the appearance can be wrong. Of course the appearance can be wrong. But nevertheless, it is your sense observation and sense testing that is the basis. It’s not some arbitrary decree — not “God said it, I believe it, that settles it.” You could be very dogmatic and say the sun is X miles in diameter, but those assertions are based on a scale of measurement we ourselves selected through the senses and decided was the best way to measure. To begin to cite some specifics of the Geller Goade article: he does a very good job of summarizing the background of the issue and reaches some conclusions of his own about how the Epicureans continued to use this formulation. The same formulation appears in Lucretius several hundred years after Epicurus, without much change, and the Epicureans clearly saw it as serving a couple of different purposes. Geller Goade says it becomes a sort of litmus test — a shibboleth — and that it is an in-your-face statement that if you’re going to understand Epicurean philosophy, you’ve got to understand that the senses are ultimately at the root of all efforts to determine what is true.
Joshua: There are two main points I want to articulate here on the size of the sun. The first: while we can’t get closer to the sun, we can set things against it to create another frame of reference. Greece has a lot of coastline and a lot of mountains. If you set a trireme on the horizon against the setting sun and the sun is larger than the trireme, you know the sun is at minimum bigger than a trireme. If the sun sets over a distant mountain and doesn’t get eclipsed by it, you know the sun is bigger than that mountain. But Epicurus can only carry that so far — he can’t set everything against the sun — and we keep circling back to the fundamental problem: we simply cannot get close enough to either of these bodies to have any confidence about our conclusion.
The second point concerns a passage that I believe comes later in this letter — on eclipses. One of the explanations he gives for a lunar eclipse is the interposition of the earth between the sun and the moon. That explanation really only makes sense if the scale of the moon and sun is at least comparable to that of the earth. If the sun were a foot in diameter, that explanation doesn’t work at all. So embedded in the multiple-explanation approach is the clear allowance that the sun and moon may be much larger than they appear — which is exactly what he says here: “In reality it is either slightly greater than what we see, or slightly less, or the same size.” We simply can’t know. That is the main point.
Cassius: And as to the reasons this issue is important — positively, it affirms the basis for proper reasoning from observation. From a confrontational point of view, it’s important to understand because it is used against Epicurus to ridicule him: “Ha — he thought the sun was no bigger than a foot, and anyone so ridiculously stupid obviously has nothing important to say about anything.” Every time someone makes an argument like that, what they’re really saying is that this person is so stupid he cannot even observe the things we ourselves observe — and that’s what you were just saying, Joshua. You see the sun setting behind a mountain, you see the sun larger than a ship at the horizon, and you know the sun has to be larger than those objects. So why would anyone take the position that it could be no bigger than your foot? You always have to ask when dealing with lawyers what their biases and motives are — and Cicero was trying to make Epicurean positions look ridiculous because he wanted to make all of Epicurean philosophy look ridiculous. He doesn’t give a balanced presentation. I can’t say enough good things about the Geller Goade article on this. He talks about the history of argumentation on this issue, does a very good job of marshaling the evidence, and carries it to what I think is the right conclusion — that this is something the Epicureans were using as a litmus test, a method of teaching the essence of Epicurean epistemology: you don’t back down on something just because it sounds funny the way you say it. And that is something that comes up repeatedly in Epicurean philosophy — think about how Epicurus had a very different definition of “god,” or that he used words in non-standard ways.
Martin: I pretty much agree with everything said. Nothing to add at this point.
Cassius: Martin, in your own work in science — is it accurate to say that our ultimate measurements are always comparisons of one thing to another, and that the unit of measure is ultimately something we selected using the senses and deciding what was the best standard?
Martin: Yes, it’s correct. And I think DeWitt captures the issue — the confusion of the bricks of the wall versus the ruler or the straight edge that you use to construct a wall that is uniform and stands up. Those are two different things.
Cassius: Thank you, Martin, for correcting me on the current definition of the meter. Now there are two other points I’d like to get in — one about culture and one about methods of instruction — and both come primarily from the Geller Goade article. On methods of instruction: by the time you’ve been reading Lucretius’s long-form didactic poem and you get to this passage where he claims the size of the sun is to us as it appears, it presents what Geller Goade calls a didactic challenge to the reader. You’ve gotten this far, you’ve understood “nothing from nothing,” you’ve grasped atomism, you’ve worked through some of the problems with religion — and now you read something that makes you stop and do a double take. He compares it to the plague at the very end of Book 6, which closes without giving you a summary conclusion about what to think, but instead leaves you with a shocking example from real life that you’re implicitly challenged to analyze in terms of everything you’ve already learned. That’s what this passage does in a similar way — it challenges you to go back and think: why would he say this? What direction is he going in? For every ten readers who decide he’s just an idiot and walk away, if he reaches a few who say “this man is too smart to have said something obviously wrong — he must have a point behind this,” that’s what he’s after.
The second point is the shibboleth argument. Prior to Epicurus you have Anaxagoras, who did give an approximate measurement of the size of the sun — he said the sun is a mass of blazing metal larger than the Peloponnese. And Anaxagoras was more than an outlier on that point. It was partly because of his astronomical claims that he was sentenced to death — condemned to die by the leaders of Athens — and it was only by fleeing to Lampsacus that he was able to preserve his life. Then a generation after Anaxagoras you have Socrates, again accused of impiety, again condemned to die. And about a generation after Socrates you have Epicurus. He knows he is making claims that are countercultural, that are abhorrent to the authorities who have power over his body and his ability to go on living. And it might occur to him — dovetailing with the shibboleth argument — that this formulation is a way to express his opinions about astronomy in a way his students will understand but that will not be an overt threat to established authority and its orthodoxy.
Joshua: Cassius, I’m curious how you would take that line of thinking, because I know it’s quite important to you that Epicurus said what he meant and meant what he said. And yet, on this — if you’re going to accept that the size of the sun becomes a shibboleth for Epicureans, that they continue to say this knowing that people outside Epicureanism will hear it and come to exactly the wrong conclusion, that does present something of a problem. But I’d be curious to know your opinion.
Cassius: I think you’ve articulated it very well, Joshua, and I didn’t have any problem with what I was hearing — it’s almost like the issue of talking favorably about pigs as a slogan and mascot for Epicurean philosophy. I think it serves several purposes at once. And that’s also why it’s so good to have you back on the podcast. These stories you bring — and Geller Goade makes the point as well — is that saying the size of the sun is as it appears is a way of doing what the plague at the end of Lucretius Book 6 does: it closes without telling you what to conclude. It challenges you to say: why in the world would he say something like this? And for those who think it through, the conclusion is that maybe meters, feet, miles, and kilometers are not handed down from God on Olympus or Mount Sinai — that the real important truths of life come through observation, and saying the size of the sun is as it appears serves as a shocking challenge that leads you in the direction of understanding that ultimately observation is the better course for determining what is true.
Joshua: And you’ve just touched on what I wanted to close with. This idea of being mocked rather than killed may have had some influence here, because prior to Epicurus — and well after — the fruit of speaking frankly on some things was to come to an end like Giordano Bruno. During the Renaissance, Bruno reads Lucretius, is convinced by it, falls for this idea of an infinite and eternal universe made of atoms and void with other worlds like ours that are inhabited. And like Anaxagoras before Epicurus, he comes to an end Epicurus managed to avoid. According to his captors, Bruno was unwilling to recant — unwilling to go against anything he said. He was questioned for nine years, imprisoned by the Church, and ultimately killed in the Campo dei Fiori in Rome — burned at the stake by Cardinal Bellarmino because of views like this one. So for Epicurus to express this in the way that he expressed it, and for Geller Goade to isolate this thread — the shibboleth, the way of speaking to Epicureans in a way that outsiders may not understand — that is the fruit of Frank speech under certain conditions. I have to hammer home that this article by T.H.M. Geller Goade is absolutely essential reading on the size of the sun. That will be my closing statement.
Cassius: And I’ll echo that — this article is a very thorough, academically vetted presentation of the issue. It’s one thing for those of us who are more casually into philosophy to do the best we can, but we haven’t gone through the rigors of advanced degrees in these issues, haven’t had the time to collect all the citations and read what people have previously said. This is the kind of well-cited, well-referenced discussion that comes to a very assertive conclusion about what’s going on here. If you just read that Epicurus held the size of the sun was about a foot or about the size of a basketball and you walk away from Epicurus because of that, then this passage really does serve as a test — a litmus test — a puzzle you’ve got to be able to work through before you’re going to get the benefit of what Epicurus had to say.
This is one of those intersections of physics and ethics that’s so important to understand. Ultimately it’s the senses — and although it’s beyond the scope of today to discuss whether pleasure and pain and feelings are really the same as a sense or not — ultimately this is one of those areas that connects our ethics, which is based on the feeling of pleasure as we feel it ourselves, with how physics also operates: according to our observations, with the ultimate standard for what we conclude to be true coming from whether we can reproduce it and prove it through observation. In ethics it’s the experience of pleasure and pain that is the ultimate standard. The word “experience” is very important — if you cannot feel it, sense it, validate it through your personal faculties, it’s not as real to you as something you do validate yourself.
We’ve gone on a little bit long today. We’ll come back next week and continue with the Letter to Pythocles. Before we close — Joshua, is there anything else in the rest of the text you wanted to address?
Joshua: No, I don’t think we’ll get to it today. I do need to look into the second paragraph of section 92 — there seems to be a lacuna, a corruption in the text, and I need to find out how that affects how we read the line. We can come back to that next week.
Cassius: Yes, and we can address that next week as well — the whole letter continues with these astronomical and celestial atmospheric issues, so we’ll continue with the moon and reflected light and so forth. Thanks very much, everyone. Martin, anything to add for today?
Martin: Nothing to add.
Cassius: And Joshua, anything else?
Joshua: Just that it’s great to be back. I’ve enjoyed this conversation. Thanks and bye.
Cassius: See you soon. Goodbye.
Martin: Thank you. Bye.