Lecture 7 — How colors are generated

But to say, like the ancients, that color is an emanation, and is seen due to such a cause, is incoherent. For in any case it was necessary for them to make sensing occur through contact. Therefore it is better to say at once that sensing occurs by the medium of sensing being moved by the sensible object, than by contact and emanations.

Accordingly, in the position that bodies are juxtaposed, just as it is necessary to assume an invisible magnitude, so it is also necessary to assume a length of time imperceptible to sense, so that the movements escape notice as they arrive, and it is thought that they are one thing because they appear simultaneously.

But in the latter case there is no such necessity: rather, the color that is on the surface, being immobile, and moved by the one placed under it, will cause a movement that is dissimilar, and so something else will appear, and it will be neither white nor black.

Therefore if it cannot be that any magnitude is invisible, but any one is visible from some distance, this latter case, too, will be a mixture of colors. But also in the former way, nothing stands in the way of a common color appearing to those who are at a distance. For that there is no magnitude that is invisible is to be considered in what comes after.

But there is mixture of bodies not only in the way that some think there is: by minimal parts being juxtaposed, but being unapparent to us because of the sense power. There is also that of a whole being wholly mixed with a whole, as was said of all bodies in the discussions of mixture in general. For in the former way only those things can be mixed that can be divided into smallest parts, like men, horses, or seeds: men can be divided to a man, and horses to a horse. And so, by juxtaposition of these there is mixed together a multitude that consists simultaneously of both. But we do not say that one man is mixed with one horse. But whatever is not divided into a smallest part cannot be mixed in this way, but by being mixed from the whole, and such things are by nature mixed most thoroughly. How it is possible for this to occur was said before in the discussions on mixture.

But at the same time it is clear what necessity there is, when these are mixed, for colors also to be mixed. And this—not overlay, nor juxtaposition—is the principal cause of there being many colors: for it is not just from a distance, and not close up, that one of the mixed colors appears, but from anywhere.

And there will be many colors because what is mixed together can be mixed in many proportions, some on the basis of numbers, but some according to difference alone. And the other things that were said about colors placed beside one another, and about overlay, can similarly be said of mixtures also. But the cause of species of colors, and those of flavors and of sounds, being limited and not infinite, must be considered later.

What color is, then, and the cause of there being many colors, has been said. But about sound and voice something was said before in the discussions On the Soul.

105. But to say, like the ancients (440a15). Having presented two ways of generation of intermediate colors, here he compares the ways mentioned to one another. On this point, he does three things.

First, he eliminates a position from which one of the ways mentioned followed.

Second, he compares the ways mentioned to one another, where he says accordingly, in the position that bodies are juxtaposed (440a20; [108]).

Third, he shows how far each of the ways mentioned can be maintained, where he says therefore if it cannot be that any magnitude is invisible (440a26; [112]).

Accordingly, he first says that the ancients held that color is nothing but an emanation from bodies that are seen. For as was said above, (Cf. cc. 2–4, nn. 46–51, 60.) Democritus and also Empedocles held that vision occurs from such a cause as this, namely emanation of “idols” from bodies that are seen. And because everything is seen by means of its own color, they believed that color is nothing but this emanation. But to say this is completely incoherent.

106. For they could not hold that these bodies emanating from bodies seen enter inside the eye, because thus its substance would be destroyed. Hence in any case they had to hold that vision occurs through contact of the released bodies on the eye itself, which by this contact is altered to a state of seeing. Hence if such alteration suffices to cause vision, it is better to say that vision occurs by the medium being immediately, from the beginning, moved by the sensible object, than to say that vision occurs through contact and emanation: for nature provides for herself by means of as few things as possible.

107. But there are also other considerations that show the abovementioned position to be false.

First, because if vision occurred by contact, the sense of sight would not be distinct from touch, which is clearly false, for sight is not apprehensive of the contraries of touch.

Second, because bodies seen through continuous emanation would be diminished, and finally completely used up; or if their quantity were preserved by other emanations coming to them, <. . .>.

Third, because since these bodies emanating from things seen would be extremely fine, they would be driven by the winds, and so direct vision would not occur.

Fourth because sight would not need light for seeing, since vision would occur through contact of the visible.

And many other such inconsistencies follow, which, because they are obvious, the Philosopher passed over.

108. Then when he says accordingly, in the position that bodies are juxtaposed (440a20), he compares the two ways mentioned to one another.

Here it must be considered that the first way of generation of intermediate colors was given by those who held that color is an emanation; and so, after Aristotle shows the falsity of the position in itself, he concludes to an inconsistency that follows for them in this way of explaining the generation of colors.

He says that in holding that intermediate colors are generated by the extreme colors being juxtaposed, it is necessary for them to say not only that there is a magnitude that is invisible, but also that there is a length of time that is imperceptible, to maintain their proposal. For because they held that vision occurs through local motion of emanating bodies, and because nothing is moved any distance by local motion except in time, they must assign some time in which the emanation from the thing seen to the eye occurs, and they must posit a greater time to the extent that there is greater distance.

109. Now it is clear that there is not the same distance to the eye for all the infinitesimal bodies juxtaposed, and thus there must be different lengths of time in which the movements from them reach the eye. Therefore the whole composed of such bodies will not be seen as one thing, as was held above, unless the time in which one movement precedes another escapes notice, in which case it is necessary to posit an imperceptible length of time in this way of explaining the generation of colors.

But in the latter case—that is, in the second way—there is no necessity for an imperceptible length of time to be posited, because it is not held that vision occurs through emanation by local movement. But although the color placed on the surface remains immobile with respect to place, it is nevertheless changed by way of alteration by the color underneath, so that it affects sight in a way dissimilar to that in which either the color placed on top or the one placed underneath would of itself. Hence another, intermediate color will appear, and it will be neither white nor black.

110. Now it must be considered that, even if we set aside the generation of intermediate colors that they posit, it follows for those who hold that sight occurs through emanation and contact that there is a length of time that is imperceptible. For they must say that any whole body is not seen all at once, but only through a succession of time, since they hold that sight occurs by contact, and it is not possible for a whole large body or its emanation to be touched all at once by the pupil, because of its smallness. And so it follows that there is an imperceptible length of time, since in the case of some things, it does seem to us that we see the whole of them all at once.

111. But it must be considered that a body that presents itself to sight can be considered in two ways.

In one way according as it is one whole in actuality, and its individual parts existing in it are in a way in potentiality: thus vision is directed to the whole all at once, as a unit, but not determinately to any part of it.

In the other way, a body that presents itself to sight can be considered according as a part of it is taken as determinate in itself, and distinct, as it were, from other parts. And thus sight is not directed to the whole all at once, but to one part after another. And this time by which the sight of the whole is measured is not simply imperceptible, since the soul, in sensing before and after in movement, senses time, as is clear from Physics 4. (Aristotle, Physics 4.14, 223a21–29; cf. Aquinas, Commentary on Physics, bk. 4, lect. 16–17.) But this time is more perceptible to the extent that the sense power is sharper, and greater attentiveness is applied.

112. Then, when he says therefore if it cannot be that any magnitude is invisible (440a26), he shows how the two ways of generation of colors can be maintained, and how far they extend, namely to appearance.

He concludes from what was said above that, if it cannot be that any magnitude is invisible, but any magnitude is visible from some distance, it indeed follows that there will be a mixture of colors, that is, by layered colors. And also in the former way—that is, by placing of colors next to one another—nothing prevents a common color from appearing from a certain distance from which neither of the simple colors can be seen because of the smallness of the bodies. But that no magnitude is simply invisible because of smallness he says is to be made clear in what follows.

113. Then, when he says but there is mixture of bodies not only (440a31), he presents the way of the generation of intermediate colors that is according to existence, not just appearance.

First, he determines the generation of intermediate colors;

second, he gives the reason for their distinction according to this way of generation, where he says and there will be many colors (440b18; [116]).

But because this way of the generation of intermediate colors is understood in relation to mixture of bodies,

first, he prefaces something about mixture of bodies,

and second, he adds something about mixture of colors, where he says but at the same time it is clear (440b13; [115]).

Accordingly, he first says that mixture of bodies with one another does not occur only in the way that some thought—namely by some infinitesimals being juxtaposed with others, all of them being unapparent to our senses because of their smallness. Rather, some bodies can be totally mixed into one another, in such a way that whole is mixed with whole, as was said in the book On Generation, (Aristotle, On Generation and Corruption, 1.10, 327a30–328b22; cf. Aquinas, Commentary on Aristotle’s On Generation and Corruption, bk. 1, lect. 25.) where there was treatment of mixture of bodies in general.

But it is true that some things are mixed in the former way—that is, by juxtaposition of minimal parts—namely whatever can be divided down to smallest parts, as a multitude of men is divided down to one man as its one smallest part, and a multitude of horses down to one horse, and a multitude of seeds down to one seed, i.e., one grain of wheat or some such thing. Hence it can certainly be said that a multitude of such things is mixed by the smallest parts being juxtaposed, for instance if men are confusedly mixed with horses or seeds of wheat with seeds of barley. However, the mixture of such things will not be total, for individual parts of the multitudes will remain unmixed, because one man will not be mixed with one horse, nor any other such thing with any other.

114. But whatever is not divided into a smallest part—that is, bodies that are continuous and have similar parts, such as wine and water—is not mixed in the above-mentioned way—that is, by juxtaposition of smallest parts—because one cannot take a smallest part in them. Rather, it happens by a whole being mixed with a whole in such a way that no part remains unmixed. And such things are by nature most thoroughly—and most truly—mixed. How this can occur was determined in the book On Generation. (Aristotle, On Generation and Corruption 1.10, 328a18–b22.)

115. Then, after mixture of bodies, he touches on mixture of colors, when he says but at the same time it is clear (440b13).

He says that from what was determined above it is clear what necessity there is that when bodies are mixed, colors are mixed. For it was said above (Cf. ch. 5, nn. 90–92.) that the transparent, according as it exists in bodies, makes colors be participated, and that the transparent is found in bodies in different ways, namely according to more and less, as is also likewise brightness. And so when bodies, in which there are brightness and the transparent, are mixed, a mixture of colors necessarily occurs, and this is the principal cause of there being many colors besides white and black. The principal cause is not overlay—that is, one color being placed over another—nor is it juxtaposition—that is, infinitesimal colored bodies being placed next to one another—because an intermediate color besides white and black appears not just from afar and not close up, but from any distance. Thus it is clear that this is the way of the generation of intermediate colors according to their existence, but that the other two ways pertain only to their appearance.

116. Then, when he says and there will be many colors (440b18), he gives the cause of the distinction of intermediate colors according to the way of generation just described.

He says that many intermediate colors are generated because bodies can be mixed together in many proportions, and consequently so can colors themselves: some according to determinate numbers, but some according to incommensurable difference alone. And all the other things must similarly be said here about mixture that were said above in the other two ways, namely juxtaposition of colors and imposition of one color over another. (Cf. ch. 6, nn. 97–104.)

There is one thing that remains to be determined later, namely why species of colors, flavors, and sounds are finite and not infinite. (1.6, 445b20–29, 446a16–20; cf. ch. 14, nn. 208–23.)

117. Finally, by way of epilogue, he concludes that it has now been said what color is and the cause of there being many colors (440b26). He excuses himself from a determination of sound and voice because a determination was already made about these in the book On the Soul. For the account of their generation is the same as that of the alteration by which they alter the sense power, which pertains to the consideration of the book On the Soul. (Aristotle, On the Soul 2.8, 419b4–421a6; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 16–18, nn. 439–78.)