Purity, Light and the Transparent: Aristotle's De Anima II.7 and Empedocles' Photons

Orientation #

He refers back to “the same reasoning as you brought out last time” on why one virtue is called purity (a student’s remark, prev. lecture), and says he will hand out a passage from Thomas’s commentary on the De Sensu et Sensato for the things seen in the dark; touch and the medium “we’ll see … when we get there.” Last time treated chapter 6 and the three kinds of sensible; next time treats the De Sensu on sight and hearing.

The class, in order #

1. Pre-class: purity, “the very wrath of love”, temper, life’s voyage (“they’re in the very wrath of love”) #

Loose opening exchange on words that name the moderation of a strong passion and then get confused with the passion itself.

• Student: Thomas uses pudicitia (from pudor, shame) rather than puritas, though the reasoning is the same. He: we say “pure” all the way up to God as pure act; but one virtue in particular is called purity because sensible pleasures most of all “contaminate the soul”, they “drown reason.”
• Shakespeare, As You Like It (Oliver and the cousin): “they’re in the very wrath of love, clubs cannot part them” — as two fighting dogs are parted only by a club, so this couple; a funny metaphor, but apt because lust and anger are both strong emotions needing moderation. Hence Thomas in the Summa Theologiae, after the four cardinal virtues, puts mildness (moderating anger) with temperance.
• “Temper, temper”: originally the temper was what moderates anger; now “temper” means the anger itself — the moderation confused with the excess, “just like here they’re confusing the end with the natural result of the end.”
• Student: does “wretched” connect with “wreck”? Yes, shipwreck. Life as a voyage trying to reach port (Romeo as sea captain; “life’s uncertain voyage”; the waves as symbol of this world in church documents; the fish put up on the shore in John’s Gospel, out of the tumult). Old sea insurance was a bet on whether you came back — dangerous days, so the metaphor was better.
• Asides: Conrad Lorenz could make the different bird calls (told “you’re talking goose” to ducks); cats have different meows we don’t discriminate; Father Groeschel’s father: “do you really feel safe flying without insurance?”
• Talking philosophy with a friend: in daily life you don’t distinguish seeing his color from seeing his shape; “it’s confused”; you have to really think out that distinction.

2. The transparent actual and potential; color moves the transparent in act (“the transparent is actually transparent”) #

Point: color is by nature a mover of the transparent in act, and the transparent is in act through light; hence color is not visible without light, and light must be treated first.

• When there is light in the transparent it is actually transparent (you see through it); when dark, only able to be. The color of the bricks moves the transparent all the way to his eyes — but the transparent in act, illuminated by the sun or the artificial lights.
• Note: Thomas in many other places speaks of color as a partaking of light; here neither he nor Aristotle stresses that. Here light is what makes the transparent actually transparent so color can reach the eye through it.

3. Number 190: what the transparent is; color at the end of the transparent (“where is the color that you see”) #

Point: the transparent is visible not in itself but through an extraneous color; he prefers “what you can see through”; color is the end or limit of the transparent (the red of the bricks, the black of the gown, at the end of the air between eye and thing).

• Against the moderns (his colleague “taken up with the modern doubts”), who say we sense only the effect of things on us: ask him “where is the color that you see — up here, or out there?” Experience says the color you see is at the end of the transparent, there is always a transparent between eye and color, so the color seems to be outside the eye.
• What convinces him the color is “in a way out there too”: we know the shapes of bodies through color, and it is hard to deny the shapes are in the bodies. The children’s plastic cube with round, triangular, square holes and matching blocks: try to put the round block through the triangular hole and it won’t go — the shapes are really in the objects. (Joke: his colleague had “a great illumination” that the senses deceive; he should buy one of these toys. De Koninck: a man who has never worked with his hands won’t understand philosophy.)

4. The transparent in many things; light as its form, darkness its lack (“light is like the color of the transparent”) #

Point: transparency is a common nature found in air, water, glass and the eternal body above; light is the act or form of the transparent, darkness its privation.

• Not as air or as water that they are transparent (else water would not be), but through some nature present in both and in the body above — the spheres carrying the stars, which you see through.
• Aristotle imagines the transparent as the subject of light, “that in which” either light or its contrary — really its lack — as form is in matter: clay molded into a sphere or a cube; health making the body actually healthy. The transparent is able to be enlightened or dark; darkness is the lack of light in the transparent; light “is like the color of the transparent” when it is in act due to fire or the body above.

5. Numbers 192–193: light is not a body — and the modern photon (“wave-particle duality”) #

Point: Aristotle rejects the ancient view, revived by modern science, that light is very subtle bodies moving through space.

• History aside: Newton (particles) vs. Huygens (wave); either hypothesis explained what was seen, Newton had more authority; a 19th-century experiment favoured the wave; then Einstein 1905, annus mirabilis, three Nobel-worthy papers (photoelectric effect, Brownian movement, special relativity) — the Nobel was for the photoelectric effect, explained if light is a shower of particles, “light quanta” (after Planck), later “photon” (Greek for light; photography = “draw with light”). Hence wave-particle duality (joke: wave on Mon/Wed/Fri, particle on Tue/Thu/Sat); de Broglie in the 1920s found electrons and protons wave-like too; quantum physics attempted to resolve the contradiction. So the view Aristotle rejects is “certainly closer to what we would know from modern science.”
• Aristotle’s first reason (193): light is neither fire nor any body nor a stream from a body, but the presence of fire or such in the transparent — a quality or form of the transparent. If light filling the room were a body, two bodies would be in the same place, which cannot be. “A very good reason.”
• Second consideration: light is contrary to darkness, darkness is not a body but a lack; so light is like a form, darkness the privation of that state of the transparent.

6. Number 195: against Empedocles — the “no time” argument examined (“illumination takes no time”) #

Point: Aristotle’s argument that illumination is not a locomotion is valid in form but has a false second premise.

1. If illumination is a locomotion (the spreading in place of very fine bodies), then illumination takes time — necessary.
2. But illumination takes no time — Aristotle grants it might escape us over a small distance (“the hand is thicker than the eye”), but east to west “is a very great departure”; incredible to him and to Thomas.
3. Therefore illumination is not a locomotion.

• Form: “if A then B; not B; therefore not A” — the form met long ago, Socrates argues so; the form is good. Matter: the second premise is only probable, and in fact false: subtle experiments like Michelson-Morley measure the time, about 186,000 miles per second.
• Compare Aristotle’s argument that the stars are incorruptible (unchanged as far back as men remember, changing only in place) — treated most formally in the second book of natural philosophy, the book on the universe, in Latin De Caelo et Mundo (Greek title is really “on the universe”, ouranos). Thomas in his commentary there says the argument is not necessary: the time for the stars to change may exceed many generations. Same weakness in both arguments: one takes too little time to be noticed, the other too long. (Supernovae might give evidence.)
• Aristotle at the start of the biological works: we are in a much better position with animals, which we can examine closely, than with sun, moon and stars — a better biologist than astronomer. Darwin’s letter on reading the Parts of Animals in the English translation (translator given as “Oglethorpe” in the recording [ed.: likely Ogle]): Linnaeus and Cuvier “mere schoolboys” compared to Aristotle.

7. Digression: common experience vs. private experience; Greeks vs. moderns (“on the basis of common experience”) #

Point: chapter 7 begins to depend on private experience; the Greeks erred by pushing common experience too far, the moderns, “more irrational”, by denying it can reach anything.

• Absurdity of the modern view: as if we could not know a whole is more than its part until we know a water molecule is more than a hydrogen atom — but you must already know the first to know the second.
• The Greeks more reasonable: no one could know beforehand how far common experience reaches. If earth, air, fire and water were the first forms of matter, common experience would suffice; if there are forms before them, only ingenious experiment could bring them to light. Where the line falls isn’t clear in advance; reasonable to go as far as you can and start experiment where it breaks down.
• A principle of simplicity for experience: don’t demand more experience than is necessary — the chemical lab is needed to know water is H₂O, not to know a whole is more than a part. Sociologists’ long surveys concluding that boys and girls have different interests; the liberationist mother who bought her daughter a toy truck and found her putting it to bed; boys who make a gun of anything (Thomas on Matthew: a boy always wants something military).
• Aristotle knew biology needs private experience: he did anatomy, Alexander sent him animals and plants from the Near East; before Politics V (on revolution) he studied 150 Greek city-states. The Greeks are “less culpable.”

8. Telescope and microscope; definition and demonstration as reason’s tools (“syllogism … is a bit like the telescope”) #

Point: the moderns invented tools for the senses (telescope, microscope) but neglect the two tools logic gives reason.

• Telescope: seeing at a distance (tele, scope from Greek “look”; televisio in his high-school Latin reader); microscope: seeing small things, blowing them up. The Greeks lacked both, but “would have looked through them.”
• Definition ~ microscope: it blows a thing up so you see it distinctly — “square” becomes “equilateral and right-angled quadrilateral.”
• Republic: after Book I concludes the just man is happier, in Book II a speaker asks whether Socrates wants to seem to have convinced them or really; Socrates blows up the soul by the proportion of its parts to the parts of the city, so big you can hardly miss it. Lesser cases: reason is to the emotions as a man to a horse (emotions ruling reason = the runaway horse dragging the rider over the rocks); should reason rule the emotions as a master rules a slave or as a father his children? — as a father.
• Demonstration ~ telescope: our reason is not to the statements we want to know as a circle’s center to its circumference (equally distant from all) but as a straight line to its points; in Euclid Book I the conclusion of one proof is the premise of the next, until the 47th, the Pythagorean theorem, at some distance from the mind, while “quantities equal to the same are equal to each other” is obvious at once.
• Moderns neglect both: Mill says there are no definitions of things; some writers on the Posterior Analytics (his brother Richard is translating it) deny syllogisms — and one proves it by a second-figure syllogism (“every argument is from part to part, no syllogism is from part to part”). Thomas: logic supplies reason the tools it needs. Moderns miss much for lack of definition and demonstration; Greeks for lack of telescope and microscope — “but again, they’re more excusable.”

9. Back to the text: how many reasons against Empedocles (“basically there are two reasons”) #

Student: is this his third reason? He: basically two — 194 only recalls and emphasises what was said. First, two bodies not in one place; second, fine bodies (today, photons) would take time, but apparently it takes none. Aside: modern talk of a single photon reacting with something in the eye leads back to the photoelectric effect.

10. Number 196: the uncolored receives color (“the uncolored is receptive of color”) #

Point: the transparent lacks color of its own, which is why it can receive and convey it; likewise the sense powers and media must lack their object.

• The liquid inside the eye is colorless; a red liquid there would make everything look red or pink; a sugary tongue couldn’t taste dry wine. Problem flagged for later: the organ of touch cannot be wholly denuded of hot and cold, hard and soft.

11. Numbers 197–202: things seen in the dark; Democritus and the void; fire; media of other senses (“if what is in between should come to be void”) #

Point: the second, unnamed visible of 188 is what is seen in darkness; 198 sums up the account and refutes Democritus.

• 197: things that are fiery and shining in the dark — fungi, horns, scales and eyes of fish, the cat’s eyes; not proper color; the cause “is another story” — treated in the book On Sense and the Sensible; he will hand out a passage of Thomas’s commentary on the De Sensu et Sensato.
• 198 summary: what is seen in light is color, whose being is to be motive of the transparent in act, and light is that actuality. Sign: put a color on the eye and you see nothing — there must be the transparent between; the color moves the air, and the continuous air moves the organ.
• Democritus (atoms and the void) thought that if the between were empty we’d see more exactly — an ant in the heavens. Aristotle: seeing is the sensitive undergoing something, which cannot be by the color itself but by what is in between; with a void, not better sight but none at all. Compare sound in a true vacuum. (The void does fit the shower-of-particles idea, already rejected.)
• 200: fire is seen both in darkness and in light, by necessity, because its light makes the transparent to some extent actually transparent.
• 201: aside that other organs likewise require a medium; touch seems the exception, but Aristotle holds the skin is the medium and touch is more within — “we don’t have to get too much involved in that.” 202 goes into details for the De Sensu; the recording ends there.

His words #

• purity / pudicitia: the virtue so named because sensible pleasures most contaminate the soul, “drown reason.”
• temper: originally the moderation of anger, now the anger itself — moderation confused with excess.
• transparent (diaphanes not uttered): “what you can see through”; visible not in itself but through an extraneous color; that in which light or its lack is, as form in matter.
• in act / able to be: transparent actually transparent (lit) vs. only able to be (dark). [ed.: act / potency]
• lack: his English for privation (“to use the English word, the lack”).
• illumination: the coming-to-be of light in the transparent; Aristotle: not a locomotion.
• the book on the universe / second book of natural philosophy: De Caelo et Mundo.
• common (ordinary) experience vs. private experience: what anyone has vs. what needs experiment or special observation.
• definition ~ microscope; demonstration (syllogism) ~ telescope: logic’s two tools for reason.
• “the sensitive suffering or undergoing something”: his rendering of seeing as a being-acted-on.

Texts #

Read in class

• Aristotle, De Anima II, ch. 7, numbered paragraphs 190, 192–198, 200–202 of the class translation (light, the transparent, Empedocles, Democritus). Mentioned
• Thomas Aquinas, Summa Theologiae, cardinal virtues and allied virtues (mildness under temperance).
• Shakespeare, As You Like It (“the very wrath of love”); Romeo and Juliet (Romeo as sea captain).
• Gospel of John (fish put up on the shore).
• Aristotle, De Caelo et Mundo and Thomas’s commentary (incorruptibility of the stars).
• Aristotle, biological works (opening; Parts of Animals); Darwin’s letter on the translation.
• Thomas Aquinas, Commentary on Matthew (boys and military things).
• Aristotle, Politics V (the 150 city-states).
• Plato, Republic I–II; other dialogues (man and horse).
• Euclid, Elements I (the 47th, Pythagorean theorem).
• John Stuart Mill (no definitions of things); Aristotle, Posterior Analytics (his brother Richard’s translation).
• Aristotle, On Sense and the Sensible, with Thomas’s commentary (handout promised).

His questions #

• Why is one virtue in particular called purity? Because sensible pleasures most of all contaminate the soul and drown reason.
• Where is the color that you see — up here, or out there? At the end of the transparent, so outside the eye; confirmed by knowing shapes through color.
• Why is the transparent not transparent as air or as water? Because then the other would not be transparent; it is a common nature present in both and in the body above.
• What is Aristotle’s reason that illumination is not the locomotion of subtle bodies? Any locomotion takes time, but illumination takes no time.
• Is the form of the argument good? What about the matter? Form good (if A then B; not B; so not A); the premise “takes no time” only probable and in fact false — light’s speed has been measured.
• Are there three reasons against Empedocles? Basically two: two bodies not in one place; particles would take time. 194 only recalls.
• What are the two logical tools like the telescope and microscope? Definition (microscope) and demonstration (telescope).
• Is our reason to the statements we want to know like a circle’s center to its circumference? No, like a straight line to its points — one proof’s conclusion is the next one’s premise.
• With a void between, would you see more exactly, as Democritus says? No: nothing at all would be seen, since color acts only through the transparent in between.