Episode 050 - Lucretius - Book Four The Opening of Book Four - Images
Date: 12/27/20
Link: https://www.epicureanfriends.com/thread/1806-episode-fifty-opening-of-book-four-beginning-the-discussion-of-images/
Summary
Section titled “Summary”Episode 50 opens Book Four, recorded on December 20, 2020 (the Epicurean Twentieth — the annual celebration of Epicurus) with Elaine absent because she is among the first to receive the COVID-19 vaccine and is having a mild reaction. Charles reads the text, which opens with Lucretius’s repeated “honey and wormwood” metaphor from Book One, then provides a brief summary of what the first three books accomplished before introducing Book Four’s main subject: images, or simulacra — the tenuous figures that flow constantly from the surfaces of all bodies, carrying their shape through the air to our senses. Cassius frames this as Epicurus’s project of establishing a natural, non-supernatural mechanism for acquiring knowledge: just as the physics of atoms and void was established in Books One and Two, and the mortality of mind proved in Book Three, Book Four will show how information reaches us through material processes rather than divine revelation.
The main discussion turns on how the Epicurean image theory compares to modern science. Martin explains the physics of each sense: photons carry visual information (reflected or scattered from objects, then reconstructed by the brain); smell and taste involve actual molecules traveling from source to receptor; hearing is mechanical vibration propagating through air without any particles traveling from speaker to listener. Martin raises a geometric objection to the “membrane” model — a membrane flying outward perpendicular to a body’s surface would spread and dilate, delivering only a partial cross-section to the eye, insufficient to reconstruct the whole object. Cassius acknowledges the modern difference but notes it doesn’t undermine the Epicurean core point: there is a natural, material, analyzable process by which sensory information travels, and it is not supernatural. The pinhole camera and Archimedes’ mirrors are raised as ancient evidence that something physically travels through the air during vision. Ibn al-Haytham (c. 1000 AD) is identified by Martin as the first systematic theorist of optics, whose work was preserved in Arab scholarship but effectively lost to European tradition until later rediscovery.
The episode closes with Cassius framing the critical theme for Book Four: Epicurus is often criticized for claiming “all sensations are true,” but the entire substance of Book Four — which will cover distortions, illusions, the varying clarity of perception under different conditions, and the need to compare and test observations — shows that Epicurus fully understood sensory reports require analysis before conclusions can be drawn. The “true” in “all sensations are true” means the sensation is reported honestly by the sense organ, not that the immediate report is the final word on what is actually there. Book Four will continue through images, illusions, epistemology, and eventually to dreams, sex, and love at its close.
Transcript
Section titled “Transcript”Cassius: Welcome to Episode 50 of Lucretius Today. I’m your host, Cassius, and together with my panelists from the EpicureanFriends.com Forum, we’ll walk you through the six books of Lucretius’ poem and discuss how Epicurean philosophy can apply to you today. Be aware that none of us are professional philosophers and everyone here is a self-taught Epicurean. 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. For anyone who’s not familiar with our podcast, please check back to Episode 1 for a discussion of our goals and our ground rules. If you have any question about that, please be sure to contact us at EpicureanFriends.com for more information. In today’s episode, we begin Book 4 and we carry the discussion up to approximately Latin line 109. Let’s join the discussion with Charles reading today’s text.
Charles: Inspired, I wander over the Muses’ seats of difficult access, and yes, untrod. I love to approach the purest springs and thence to draw large draughts. I love to crop fresh flowers and make a noble garland for my head from thence, where yet the Muses never bound another’s temples with a crown like mine. And first I write of lofty things and strive to free the mind from the severest bonds of what men call religion. Then my verse I frame so clear, although my theme be dark, seasoning my lines with the poetic sweets of fancy — and reason justifies the method. For as physicians, when they would prevail on children to take down a bitter draught of wormwood, first tinge the edges of the cup with sweet and yellow honey, that so the children’s unsuspecting age, at least their lips may be deceived, and take the bitter juice — thus harmlessly betrayed but not abused. By tasting thus they rather have their health restored. So I, because this system seemed severe and harsh to such who have not yet discerned its truth, and the common herd are utterly averse to this philosophy, thought it fit to show these rigid principles in verse, smooth and alluring, and tinge them, as it were, with sweet poetic honey, thus to charm your mind with my soft numbers, till you view the nature of all things clearly and receive the usefulness and order they display.
Now since I taught what are the first principles of all things, and how they differ in their figures, and wander of their own accord urged on by eternal motion, and how of them all beings are first formed, and I have shown the nature of the mind, of what seeds composed, and how it exerts itself united with the body, and separated from it, how it returns to its first principles again — I shall now begin to explain what is of the nearest concern to these inquiries, and prove that there are what we call the images of things, which, like membranes or films flowing from the surface of bodies, fly every way abroad through the air. These, while we are awake, often rush upon our minds and terrify us, and likewise sleeping, when we think we see strange phantoms — specters of the dead — which shake us horribly when fast asleep. For sure we are not to imagine that the souls are broke loose out of hell, or that the ghosts hover and play about the living, or that any part of us remains after death, since a soul and body once dissolved return severally to their first seeds from whence they were produced.
I say then that images or tenuous figures are always flowing or sent out from the surface of bodies, which may be called the membranes or the bark of things, and these several images bear the same shape and form as the particular body from whence they flow. This requires no extraordinary apprehension to conceive, for to give a plain instance: many things emit bodies from themselves — some more rare and diffused, as wood, from which issues smoke and fire of vapor; others more dense and compact, as when grasshoppers in summer cast their old coats, newborn drop the pellicules in which they are enclosed, or as the winding snake leaves a skin among the thorns, for the briars we often see adorned with their light spoils.
This being so, it follows that a very subtle image may fly off from the utmost surface of bodies, for there can be no reason given why these, and not others more thin than these, may not fall off and be discharged, especially since in every surface there are many minute corpuscles that may be cast off in the very same order they are arranged in the body, and so preserve their old form and figure. And they are the readier to fly off because they are small, and not so liable to be stopped, and are placed likewise upon the utmost surface.
For it is certain that many particles are not sent out and got loose only from the middle and inward parts, as we said before, but color itself is discharged from the surface of bodies. And so curtains, yellow or deep red or blue, as they hang in lofty theaters, waving and flowing on the pillars with the wind, do this — for they stain the stage, and scenes, and audience, senators, matrons, and the images of the gods, and cause them to wave in their own gaudy dye. And the more the walls of the theater are darkened and the daylight shut out, everything which is spread over and shines out with a brighter luster. Since therefore these curtains discharge their colors from the surface, all things by the same rule may emit subtle images, for those are thrown off from the surface as well as these.
There are therefore certain images of things, of a fine and subtle texture, that are always flying about and are impossible separately to be discovered by the eye. Besides, all smell, smoke, vapor, and other such things fly off from bodies in a diffused and scattered manner, because as they pass to the outside of bodies from within, they are broken and divided by the crooked pores they must make their way through. The road they are to take is full of windings as they attempt to rise and fly out.
On the contrary, when the membrane of color is thrown off, there is nothing to disorder it, because it lies disentangled upon the very surface. And then, since the forms that appear to us in looking-glass and water and all polished bodies are exactly like the things whose images they are, they must necessarily be composed of the images that flow from the substance of the things themselves. For why those particles should fall away and be discharged from bodies which are discovered by the eye, rather than these that are more thin and solid — no reason can be properly assigned.
Charles: That was an odd paragraph. I have more trouble with that one than usual.
Cassius: Yes. Okay. Well, thanks for reading that one, Charles. A couple of housekeeping matters as we get started today. First of all, Elaine is not with us. We’re recording this on December 20th of 2020, and the event that has kept Elaine away is that she’s one of the first to be taking the COVID-19 vaccinations, and she reported to us this morning that she’s having some reaction — which hopefully is minor and actually might be a good thing. But at any rate, she’s not with us this morning. So we’re starting off Book Four here with Charles and Martin and I. Elaine will hopefully be back next week.
And so today, as we go into what Charles has just read, most of it is something that we’ve covered before in principle. We probably ought to start Book Four sort of the same way that Lucretius is doing here — by reviewing where we’ve been and why we’re here — using the text as a jumping-off point for that.
Cassius: So to start with this first passage: the one about being inspired and drinking from the fountain of the Muses is repeated from somewhere in Book One. The whole issue about Lucretius writing a poem to rim the cup with honey and make a philosophy that can be bitter to some more palatable is something we’ve discussed before. We probably don’t need to go too far into it today.
But what I would like to make sure we’re together on before we go further is that Lucretius next turns to his own summary of where we’ve been. I’d like for us to do that too, as we’re starting Book Four. What have we already covered in Books One, Two, and Three?
Book One — in the second paragraph of the text just read, Lucretius says: “now since I taught what are the first principles of all things and how they differ in their figures and wander in their own accord urged on by eternal motion and how they’re formed.” I think that’s basically Book One — the nature of the universe and atoms and void. Do you guys agree?
Charles: Generally, yes. And a bit about what was brought up in the first paragraph — a lot of the poetic imagery, especially when he talks about the legacy and reverence he has for Epicurus. Book One had a lot more of that.
Cassius: And, Charles, what you just said about the first paragraph — one line of it that I want to repeat is where he says “I write of lofty things and strive to free the mind from the severest bonds of what men call religion.” That is certainly a theme of everything. One of his purposes is to free people from the bonds of supernatural religion. That’s certainly something we need to keep in mind throughout the poem. And that’s also brought up quite a bit in Book One, especially with the very famous line about the evil that religion is able to persuade men to do.
Cassius: So if that’s basically what Book One started with, what did we accomplish in Book Two? In the first line of the second passage he goes on from discussing how things are formed, then starts talking about how he’s shown the nature of the mind and what seeds compose it, and says how it’s united with the body and separated from it. So he’s collapsing a lot of things there. Book Two — isn’t that a lot more detail about how atoms combine with each other and more detail about how atoms form everything?
Charles: Yes, atoms in void form everything. I think maybe I’ve noticed this before: I realized that the structure of the book and how Lucretius disseminates the topics mirror a lot of the order that Diogenes Laertius introduces Epicurus’s letters, and also how we on the forums view the right things to teach others about the philosophy first — starting off with the fundamentals, primarily the physics and the atoms, that there is no afterlife, there is no supernatural god, and then moving on from there.
Cassius: Right. Martin, feel free to jump in at any point. I noticed in looking at some of my notes on Book Two that he’s definitely continuing the theme there that there’s no supernatural force over nature. In Book One, he really introduced atoms and void. And Book Two continued the implications — to show how what he taught in Book One leads you to the conclusion that there’s no supernatural control over everything, that everything operates naturally without the control of a supernatural God, including the issue of human life arising from things that are nonliving. If he’s introduced in Book One that atoms and void exist and compose everything, one of the points he makes in Book Two is that these atoms and void are not themselves living things. So living things — which concern us the most — are composed of nonliving, non-supernatural elements.
And Charles, you made a point earlier about how Book Two begins to contrast Epicurus’s viewpoints against other philosophers in more detail than was done in Book One. The issue of whether living things are made of living particles, whether intelligent things are made of intelligent particles — particular philosophers were associated with different positions on those things in Book Two, showing how Epicurus differed from them.
Cassius: And so then Book Three, which is probably the easiest to characterize, was focused on how the mind or the spirit — however you want to characterize your conscious self — is not supernatural, but is indeed united with the body and cannot survive after death. That it is dissolved just like the rest of the body when you die and does not go to heaven to be rewarded or held to be punished. It simply ceases to exist at death.
So from a very broad point of view, everything we’ve discussed up to this point fits within the purpose that Lucretius is stating: to free your mind from religion. He’s setting up a theory of the universe that is entirely natural and not governed by supernatural forces — in which you’re not divine and do not continue after death or exist before birth. He’s setting up a theory that can free the mind from what he would consider to be superstition.
Cassius: So to keep pontificating for a few more minutes — we’re now in Book Four, and what we’re introducing today is the subject of images. That’s something I also want to talk about before we get too far into the details, because he’s set up the nature of life and how things operate, and now what he seems to be attacking is the issue of knowledge. How do we gain information about the universe? How do we gain information about ourselves and about other things? And how do we do that in a way that is natural and not supernatural?
This is where I definitely want to get Martin’s participation. So we’ve set up a universe based on particles in the void. And I think Lucretius sees the need to come up with a procedure or a mechanism by which we interface with, come into contact with, and gain information about the rest of the universe — also not supernatural. In other words, we’re not going to have divine revelation. We don’t gain information about the things around us because God implants it in our heads. We have to have some method of observing things.
Since everything is made of particles and void in the Epicurean universe, particles — or some kind of transmission of matter from that thing to us or from us to that thing — are going to have to be involved. The term that we’ll probably use the most is “images.” The discussion for a lot of the rest of Book Four is going to be the nature of how particles move across space from the things we see to us, or from us to those things we see. And then there are implications — the particles can get distorted or pushed in a way that sometimes we observe things more clearly than others, and we have to determine under what conditions we can trust our observations, and what kinds of distortions could cause misunderstandings.
Cassius: Okay. And with all that, this is where I want to get Martin involved — from the point of view of the current science about light. Honestly, it’s more clear to me that when we smell something, we are actually receiving particles. Like if you smell something, intuitively I understand that maybe there’s some kind of particle of scent coming out of the flower that travels through the air and comes into our noses. That seems pretty uncontroversial. But when we see something — are there actual particles moving from the thing we see into our eye? I presume there are particles from us flying in all directions at all times as well, but in terms of sight, which I think is predominantly what we’ll be talking about in Book Four, are there actual particles that fly from the other thing to us or not?
Martin: Yes, there are photons. I mean, it may not be obvious in every model — we need to be aware that it’s a model. But taking this seriously, we can really consider photons as, as far as we know, elementary particles. They’re not subdivided. Those are among the smallest entities Epicurus has been talking about. An example to illustrate: obviously when we look at the sun or are out in the sun, we feel warmth. Is that because some particle from the sun has impacted our body — actually traveled those many miles from the sun to us? Yes. We absorb these photons. Our skin absorbs them, or deeper tissue, because they can penetrate a bit, and that excites the atoms in their structures to vibrate more — which means temperature increases. That’s why we feel the warming effect when exposed to direct sunlight.
Cassius: Okay. But to bring it back to this particular text: the first sentence of the second paragraph says “I say then that images or tenuous figures are always flowing or sent out from the surface of bodies, which may be called the membranes or the bark of things, and these several images bear the same shape and form as the particular body from whence they flow.”
Now, there’s going to be a lot to parse out there, because the issue of whether those things travel in the same shape and form as the body from which they flow may not be obvious and may not be exactly correct. But I want to start with the basic issue: do we today think that there are particles flowing from things outside of us towards us? If I’m at a table across from Charles, are there actual particles flowing from Charles towards me that are received by my eye?
Martin: Yes. I mean, normally we’re not hot enough to emit light by ourselves, or we don’t have chemical reactions on our surface which would produce it. So we need a light source, which originates those photons. They hit the surface and get scattered, or reflected, or absorbed and then re-emitted. And the portions of those which reach our eyes — the information encoded in them is then reconstructed by the brain as an image.
Cassius: Okay, and so in the situation where we’re not generating a light source ourselves, it’s basically reflected or bounced off of us. But so the current science is: it’s not just that the air between me and Charles vibrates with a vibration that started with Charles and nothing is transmitted except the vibration or the wave. We actually do think that there are particles of light that move from Charles to my eye.
Martin: Yes, though it’s a bit more complicated, because the wave model is also complementarily used. The light which travels from one place to another can also be described, depending on the circumstances, as an electromagnetic field fluctuation. But even to the extent that electromagnetic field fluctuations exist, modern science has not eliminated the possibility that there are particles flowing. Modern science uses both models depending on which aspect we’re looking at and which model makes more sense in that circumstance.
Cassius: You know, maybe we should hit the five senses for just a minute. Does everybody agree that when you smell something, there’s some kind of particle that has come from the flower to your nose?
Martin: I mean, in this case it’s not a particle in an Epicurean sense — it’s a molecule. Molecules are coming from the flower, and we have cells which respond to different chemicals such that if the molecule matches what the cell is designed for, it sends a signal to the nerve, which then goes to the brain to process as a smell.
Cassius: But it is still a material transmission from the flower to our nose?
Martin: Yes, and in this case there is no complementary model. It really is a molecule coming.
Cassius: Okay. And I guess with touch and taste it’s probably easy to conclude that in both cases your skin or your tongue is coming into contact with another material substance — so I think those are uncontroversial. What about hearing?
Martin: Hearing — those are mechanical vibrations of the air. So unlike light, where we can look at it from the aspect of electromagnetic radiation, what we hear is mechanical vibrations. Air is itself molecules flying around, so we have density fluctuations of these molecules — these fluctuations then excite the receiving part in the ears and induce mechanical vibrations in those structures, which are then sensed by cells which convert this into a signal in the nerve.
Cassius: Okay, let me ask the question a different way. When Charles sitting across the table from me speaks to me, are there actual particles or molecules or any other material substance that flows from Charles to my ear?
Martin: Not for the hearing, no. I mean, of course a few molecules do come out, but those don’t contribute meaningfully to what you hear. The molecules which are excited to vibrate in these density fluctuations — they don’t reach you. It’s just that they push the neighboring molecules, and then they push the next ones. And so this propagates like a longitudinal wave and reaches you. So there, it’s just the mechanical excitation which comes over, not the actual particles.
Cassius: So we do see a significant distinction between sound and vision in terms of whether particles are actually transmitted?
Martin: Yes.
Cassius: That’s interesting. So maybe we’ll see differences in the way that’s analyzed as we go forward. So then, Martin, what do you think about that same sentence: “I say then that images or tenuous figures are always flowing or sent out from the surface of bodies, and that these several images bear the same shape and form as the particular body from whence they flow”?
Martin: It’s just — it’s not happening that way. Well, let’s talk about vision specifically. Are the photons bearing in some way the shape of what they came from?
Cassius: Yes, let’s be more clear. How does that work?
Martin: I mean, for this I would need to do drawings about how objects are imaged by lenses, and that would make it clear. So in some way, this shape is encoded in how the photons flow, but it’s not that the photons fly like a membrane. That’s not happening.
Cassius: Right. And of course, when you use the word “membrane,” that’s exactly the example he’s giving — he’s talking about grasshoppers shedding their coats, and newborn calves within the sack they’re born in, and the snake leaving its skin among the thorns. He is presenting real-life examples we’re familiar with of how a body can give off something that truly is its original shape. But that’s not — we would not say that the shape itself is preserved in the photons.
Martin: Yeah, essentially it’s encoded in how the photons fly in what pattern, and then decoded again on the other side. But it doesn’t go simply like what’s called here. And if you would think of it in this model — given the direction in which it would make sense that this membrane would fly, it would fly perpendicular to the respective area of the surface. And then that means, for a shape like that of an existing body, it would grow — the membrane would dilate. And what reaches the eye would only be a small section. So that means a membrane figured like a membrane would not aid at all in seeing a whole object. It would not be able to explain how we can see a whole object. We would not get any meaningful information from which we could reconstruct the whole object.
Cassius: Hmm. I wonder if there’s any reason to consider how images can be projected using lenses. Even in the ancient world, you can reflect an image using a mirror. I don’t know that they had glass lenses, but even holding glass up to a lighted object — or the old-style cameras that are basically pinhole. That’s a great example right there: with simply a pinhole and a closed box, you can see an image form at the other end of the box. I don’t know whether the Greeks had that or not. Martin, if the Greeks had access to a pinhole camera, or just images reflecting through glass in any way, would they relate that to what we’re talking about?
Martin: Probably. I mean, they definitely would support in some way that something is moving there, something is transported. So that is agreeable both for modern science and from practical observations at the ancient level.
Cassius: Charles, you haven’t said much lately. Any commentary on the pinhole camera?
Charles: No, not really. I know there’s something about how pinhole cameras work with how the light gets obscured in the box and all that. The only thing I can think of besides what’s being talked about right now is I’m pretty sure Aristotle didn’t experiment on that — but that’s not really related to all this.
Cassius: Well, today I just wanted to introduce the topic and get us started, because we’re going to be devoting a lot of time in Book Four to the way images work and what we can conclude from them. Even the ancient Greeks would have probably seen examples of images being projected. The mirror — looking at a pool of water and seeing a reflection — those are clearly examples they’re talking about. And if you think about what must be happening, it’s probably logical to think that something is flowing through the air.
Martin: Yes, but we need to be aware that a number of these things probably were not known to the ancient Greeks. The oldest reference I know of where someone systematically analyzed these things and put them in a concise form that is still valid today — that is Ibn al-Haytham, from about 1,100 years ago. In the textbooks, it’s usually credited to later European scientists, but this is because at that time, in Europe, the knowledge about Ibn al-Haytham’s work was lost. It wasn’t lost everywhere though — the educated Arab world knew about it, and those who came into contact with Arab knowledge would then rediscover this. Those who deal with the history of science have figured this out as well. Before Ibn al-Haytham, there was probably no accurate concept of how vision actually worked.
Cassius: Oh, one example I can think of — isn’t there some story about someone who came up with the idea of trying to burn attacking ships in the harbor by using big mirrors to focus light on them?
Martin: Archimedes.
Cassius: Archimedes. So from a practical perspective, they knew how to use mirrors. But were they using lenses?
Martin: I’m not aware if they knew how to use lenses. I mean, they certainly would have had transparent materials — jewelry, for instance — so they could play around with refraction. And like the example of a straight body looking like it has a kink at the surface of water when placed into it — so they were aware, at least qualitatively, of how refraction works. But they apparently did not make the step from there to how vision could work by reflection at the curved surface of a lens.
Cassius: Well, maybe we ought to begin to bring the discussion for today to a conclusion. But one thing I do want to begin talking about as we conclude is that Epicurus is often slammed for having made statements to the effect that all sensations are true. But I think one of the things we’re really going to get out of Book Four here is that we’re going to be spending all of Book Four talking about how sensations can be distorted and how you have to take things into account. We’ll be talking about all sorts of illusions as we go through Book Four. And the fact that he’s discussing it shows that he was fully aware that when you see something, you can’t always trust exactly what you see at first. It’s reported honestly, but it might be reported in a way that is not true to the ultimate facts.
What Book Four is doing is alerting us that there’s a process involved here that we have to understand in order to unwind the information we’ve received and produce an intelligent summary of it that is true. So that’s a very broad, high-level statement at this point in the discussion. But we’re probably getting to the end of a normal episode. So let’s talk about if anybody has any closing thoughts today, and then we’ll continue in more detail next week when Elaine is back.
Martin: I think we need to resume the last paragraph because I don’t understand the last paragraph. So to figure this one out, we need to go more in detail next time.
Cassius: Okay. Do you see immediately a way of framing your question about it that we can think about?
Martin: I just — it’s so blurred by the poetry. I just cannot put it together into something consistent.
Cassius: Okay. It was difficult reading, and yes, that’s fair. Actually, I think what I’m going to suggest next week is that this paragraph is addressing exactly what I just said a moment ago — that Epicurus is observing how the light can play tricks on us under certain conditions, and then under other conditions, such as a mirror, things can be reflected in a way that’s very exact. So we can discuss that next week, because I think the critical theme we’re going to have to follow here is that Epicurus did not teach that we should just blindly accept every sensation as being true to the ultimate fact. Once we understand the nature of how the senses work, we realize we have to test with multiple observations and even compare our observations with those from other people before we can be confident that the conclusions we draw are going to be accurate.
So Charles has been saying several times that Book Four is going to be more interesting than some of the others. And of course, we’re going to cover in Book Four all the way from images to illusions to basic issues of epistemology — all the way to sex and dreams and love at the end. The images are — beyond the concept of the Epicurean gods, I’d say images are my weakest point. But images really are the whole issue. This is epistemology. This is the issue of how we know anything. We talk in terms of images and other words that seem mysterious, but in the end, ultimately, what we’re talking about is just how we can be confident about anything based on the information we receive through the senses. So there’s a lot of really good material in this chapter.
Charles: I don’t have any closing thoughts.
Cassius: Okay. Martin, anything else in closing?
Martin: I have nothing further.
Cassius: Okay. Well, again, today is December 20th, and some of us will be getting together later today to observe the Twentieth celebration that Epicurus and the ancient Epicureans followed. So hopefully we’ll talk later today, but we’ll come back next week and continue in Book Four. All right. Thanks a lot.
Charles: Okay, thanks. Bye.
Martin: Bye.