Thomas Aquinas
Commentary on Aristotle’s
De Sensu et Sensato
tr. Kevin White
Catholic University of America Press, 2005
CONTENTS
PROLOGUE 436A1–B8
436a1 Since it was determined about soul in itself and each virtue from the point of view of it, the next thing is to make a consideration about animals, and everything that has life, as to what are their proper and what their common operations. Accordingly let the things that were said about soul be underlying, and let us speak about the rest, and first about what is first.
436a6 The greatest both of the common and of the proper features of animals are seen to be common to both body and soul.
436a8 For instance, sense and memory, and anger and desire, and appetite as a whole, and with these pleasure and pain. For almost all of these are present in all animals. And with these, some things that are common to everything that participates in life, and some to some of the animals. Of these, the greatest are four pairs in number, namely wakefulness and sleep, and youth and old age, and inhalation and exhalation, and life and death. About these it must be considered what each of them is and for what causes it occurs. But it also belongs to the student of nature to discover first principles concerning health and sickness.
436a18 For it is impossiblefor either health or sickness to occur in ilhat lacks life. Therefore, in general, in the case of most students of nature, and of the physicians who pursue the art more philosophically, the former finish with what belongs to medicine, but the latter begin medicine with what belongs to nature.
436b1 That all the abovementioned are common to soul and body is not unclear. For with respect to all, some take place together with the sense-power, some through the sense-power. And with respect to certain ones, some exist as affections of it, some as conditions, some as protections and benefits, and some as destructions and privations. And that sense is present in the soul by means of the body is clear both through discussion and apartfrom discussion.
Commentary
As The Philosopher says in On the Soul III, “just as things are separable frorn matter, so also
is what pertains to intellect”:
for everything is intelligible inasmuch as it is separable from
matter. Hence what is by nature separate from matter is of its very self intelligible in actuality;
but what is abstracted by us from conditions of matter is made intelligible in actuality by the
light of our agent intellect. And because the habits of a power are specifically distinguished
according to differentiation of that which is the per se object of the power, the habits of the
sciences, by which intellect is perfected, are necessarily distinguished according to
differentiation of “the separable from matter,” and so the Philosopher in Metaphysics VI
distinguishes genera of science according to different manners of separation from matter:
what is separate from matter according to being and nature pertains to the metaphysician;
what is separate from matter according to nature and not according to being pertains to the
mathematician; and what includes sensible matter in its nature pertains to the natural
philosopher.
And just as different genera of science are distinguished according as things are in different
ways separable from matter, so also in individual sciences, and especially in natural science,
the parts of a science are distinguished according to different manners of separation and
concretion. And because universals are more separate from matter, in natural scicnce one
proceeds from universals to what is less universal, as the Philosopher teaches in Physics I
And so he began the teaching of natural science with what is most common to all natural
things, namely inovement and principles of movement, and from there proceeded by way of
concretion or application of common principles, to determinate mobile things, some of which
are living bodies.
Concerning these he also proceeded in a similar way, dividing this consideration into three parts. First he considered soul in itself, in an abstraction, as it were; second he has a consideration of what belongs to soul according to a concretion or application to body, but in general; third he bas a consideration that applies all this to individual species of animals and plants, determining what is proper to each species. Thus, the first consideration is contained in the book On the Soul; the third consideration is contained in books that he wrote on animals and plants; the intermediate consideration is contained in books that he wrote on sorne things that pertain in common either to all animals, or to several kinds of them, or even to all living things, and the present intention involves these books.
Hence it must be considered that in On the Soul II Aristotle determined four levels of living
things. The first consists of those that have only the nutritive part of soul, by which they are
alive, namely plants. But there are some living things that, together with this, also have a
sense-power but without progressive movement, namely imperfect animals, for instance
shellfish. And there are some that have in addition forward local movement, namely perfect
animals such as the horse and the cow. And some in addition have intellect, namely human
beings. For although the appetitive part is held to be a fifth genus of powers of soul, it does
not constitute a fifth level of living things, because it always accompanies the sensitive part.
Now among these powers, intellect is the actuality of no part of a body, as is proved in On the
Soul III,
and so it cannot be considered by a concretion or application to a body or to any
bodily organ, for its greatest concretion is in soul and its highest abstraction is in separate
substances. This is why Aristotle did not write, in addition to the book on the Soul, a book On
Intellect and the Intelligible, but if he had done so, it would not pertain to natural science, but
rather metaphysics, to which consideration of separate substances belongs. But all other parts
of soul are actualities of parts of a body, and so there can be a special consideration of them
by application to a body or bodily organs beyond the consideration made of them in the book
“On the Soul.”
Accordingly this intermediate consideration must be divided into three parts. One includes what pertains to a living thing inasmuch as it is living. This is contained in the following: the book that he wrote On Life and Death, in which he determines about “Inhalation and Exhalation,” by which life is preserved in some living things, and about “Youth and Old Age,” by which the stages of life are differentiated; likewise the book entitled On Causes of Length and Shortness of Life, and the book that he wrote On Health and Disease, which also pertain to the disposition of life; and also the book he is said to have written On Nutrition and the Nourishing. We do not yet have these last two books.
Another part of the consideration pertains to the moving part of soul This is contained in two books: the book On the Cause of Movement of Animals; and the book On the Progression of Animals, in which there is a determination about the parts of animals adapted for movement.
The third part of the consideration pertains to the sensitive part of soul, concerning which consideration can be made, first, of what pertains to the act of the internal or of the external sense-power, and to this extent consideration of the sensitive part is contained in the present book, which is entitled On Sense and What Is Sensed, that is, “On the Sensitive Part and the Sensible Object,” in which is also contained the treatise “On Memory and Recollection.” Again, what causes the difference between sensing and not-sensing that is brought about by sleep and wakefulness also pertains to consideration of the sensitive part, and this is determined in the book entitled On Sleep and Wakefulness.
But because one should pass through the more similar to the dissimilar, the order of these books seems reasonably to be such that after the book On the Soul, in which it is determined about soul in itself, there immediately follows the present book On Sense and What Is Sensed, because sensing itself pertains more to soul than to body. Next in order should be the book On Sleep and Wakefulness, which imply binding and freeing of the sense-power. Then follow the books that pertain to the moving part, which is next closest to the sensitive part. And last in order are the books that pertain to the general consideration of a living thing, because this consideration to the greatest extent involves bodily disposition.
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436a1 Accordingly the present book, which is entitled On Sense and What Is Sensed, is first divided into two parts: a prologue, and the treatise, which begins where he says About sense and sensing (Chapter 1, 436b8).
On the first point he does two things. First he makes clear his intention, showing what is to be treated. Second he gives the reason why it is necessary to treat of such things, where he says The greatest (436a6).
Accordingly he first says that it was already determined about soul in its very self in the book
On the Soul, that is, where he defined soul. Again, it was subsequently determined about each
virtue—that is, power—of it, I mean from the point of view of it.
For since powers of soul,
apart from intellect, are actualities of parts of a body, there can be consideration of them in
two ways: in one way according as they pertain to soul as certain powers or “virtues” of it,
and in another way from the point of view of body. Accordingly it was determined about
powers of soul themselves from the point of view of soul itself in the book On the Soul, but
now the next thing is to make a consideration about animals, and everything that has
life—which he adds because of plants—namely, by determining what are their proper
operations—that is, proper to particular species of animals and plants—and what are
common—that is, common to either all living things, or all animals, or many kinds of
animals. Accordingly let the things that were said about soul be underlying, or
supposed—that is, let us use them in what follows as suppositions that have already been
explained. And let us speak about the rest, and first about what is first—that is, first about
what is common and after about what is proper: for that is the order required in natural
science, as was determined at the beginning of the book The Physics.
436a6 Then, when he says The greatest, he shows the necessity of this subsequent consideration.
If the proper as well as common operations of animals and plants were proper to soul itself, the consideration of soul would suffice for this purpose; but because they are common to soul and body, it is necessary, after the consideration of soul, to determine about them so that it may be known what kinds of bodily dispositions are required for these operations or affections. And so the Philosopher here shows that all of them are common to soul and body.
On this point he does three things. First he presents what he intends. Second he enumerates the features with which the intention is concerned, where he says For instance, sense and memory (436a8). Third he proves the proposal, where he says That all the abovementioned (436b 1).
Accordingly he says first that of the features that pertain to animals and plants, those that are greatest—that is, the outstanding ones—whether they are common to all animals or several, or proper to individual species, are seen, even at very first sight, to be common to soul and body. Hence they require another consideration beyond the one about soul taken absolutely.
436a8 Then, when he says For instance, sense and memory, he enumerates the features with which the intention is concerned.
First he presents what pertains to the sensitive part, namely sense and memory. He makes no
mention of the other sense-powers, namely imagination and the estimative power, because
these are not distinguished from sense from the point of view of the thing known, since they
are of present things, or of things taken as present. But memory is so distinguished by the fact
that it is of past things inasmuch as they are past.
Second he presents what pertains to the locomotive part. Now the proximate principle of
movement in animals is sensitive appetite, which is divided into two powers, namely
“irascible” and “concupiscible,” as was said in On the Soul III.
Accordingly he mentions anger, which pertains to the irascible power, and desire, which
pertains to the concupiscible. It is from these two passions, as from what is more evident, that
the two powers are named: for the concupiscible power is named from “desire” and the
irascible power from “anger” (ira).
But because there are other passions of the soul
pertaining to the appetitive power, he adds and appetite as a whole, to include everything that
pertains to the appetitive power. But all passions of the soul, whether they are in the irascible
or the concupiscible power, are followed by pleasure and pain, as is said in Ethics II.
And so
he adds, and with these, pleasure and pain, the final and ultimate passions, as it were.
He adds that these features that have been enumerated are almost all found in all kinds of
animals. He says “almost all” because most of them, narnely sense, desire, appetite, and
pleasure and pain, are found in all animals, perfect as well as imperfect. For imperfect
animals have, of the senses, only touch; they also have imagination, desire, and pleasure and
pain, although these are indeterminate in them; and they are moved in an indeterminate way,
as was said in On the Soul III.
But memory and anger are not found in them at all, but only
in perfect animals.
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The reason for this is that not everything belonging to a lower genus, but only what is highest
or more perfect, achieves a participation of likeness in what is proper to a higher genus.
Now the sense-power differs from intellect and reason because intellect or reason is of universals, which are everywhere and always, but the sense-power is of individuals, which are here and now. And so sense, according to its proper nature (ratio) is apprehensive only of what is present. But if there is a power of the sensitive part that extends to something not present, this is according to participation by likeness in reason or intellect. Hence memory, which is able to know things past, belongs only to perfect animals, being something supreme in sensitive knowledge.
Likewise, the sensitive appetite that follows from sense is, according to its proper nature (ratio) appetite for what is pleasant according to sense, and this appetite pertains to the concupiscible power that is common to all animals. But if an animal tends by appetite to something laborious, such as fighting or something similar, this contains a likeness to rational appetite, to which it is proper to desire some things for the sake of an end that are not in themselves desirable. And so anger, which is appetite for retribution, belongs only to perfect animals, because of an approach to the genus of what is rational.
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436a11 Then he presents what pertains in any way to the nature of life.
He says that with the foregoing, other features are found in animals, some of which are common to everything that participates in life, that is, not only animals but also plants; but some pertain only to some kinds of animals. And the outstanding of these are listed in four pairs. The first pair he presents is wakefulness and sleep, which are found in all animals, but not in plants. The second is youth and old age, which are found in animals as well as plants, for the life of anything subject to death and birth is divided into different ages. The third is inhalation and exhalation, which are found in certain kinds of animals, namely all that have lungs. The fourth is life and death, which are found in all living things in this lower world. And he says that about all of these it must be considered what each of them is, and what is its cause.
436a17 Because he said that the abovementioned features are the .greatest,” he adds something about some that are not so outstanding namely health and disease, which are not both found in all individual of the genera in which they exist by nature, as does happen with th( abovementioned, but which are by nature found in all living things, an imals as well as plants.
He says that it also pertains to the natural philosopher to discover first and universal principles of health and sickness. Consideration of particular principles pertains to the physician, the artisan who makes health, as it pertains to any operative art to consider particulars about its own business, because operations take place in particulars.
436a18 He proves in two ways that the former consideration does pertain to the natural philosopher, where he says For it is impossible (436al8).
First he does so by argument. Health or sickness can be found only in what has life, from which it is clear that the living body is the proper subIcci of health and disease. But the principles of a subject are also the principles of its proper attribute (passio). Hence, since it pertains to the natural philosopher to consider the living body and its principles, he must also consider the principles of health and disease.
Second bc proves the same thing by a sign or example that he conludes to from an argument that he presents. Most natural philosophers finish their study with what belongs to medicine, and likewise most physicians—that is, those who pursue the art of medicine more philosophically, not only applying experience, but inquiring into causes—begin their consideration of medicine with what is natural. From this it is clear that consideration of health and disease is common to both physicians and natural philosophers.
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The reason for this is that health is sometimes caused by nature alone, and because of this it pertains to the consideration of the natural philosopher, to whom it belongs to consider the workings of nature; but sometimes it is caused by art, and in this respect it is considered by the physician. But because the art causes health not principally, but by as it were helping nature and ministering to it, the physician necessarily gets the principles of his science from the natural philosopher as from one who is prior, as a ship’s captain gets his principles from an astronomer. This is the reason why physicians who pursue their art well start with what belongs to natural philosophy.
But anything artificial that is made by art alone, for instance a house or a boat, in no way pertains to the natural philosopher’s consideration, just as what is made by nature alone in no way pertains to the consideration of art except inasmuch as art makes use of a natural thing.
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436b1 Then, when he says That all the abovementioned, he proves the proposal, namely that all the abovementioned are common to soul and body.
He uses the following argument. All the abovementioned pertain to the sense-power. But the sense-power is common to soul and body, for sensing pertains to the soul through the body. Therefore all the abovementioned are common to soul and body.
He makes the first premise clear by an induction, as it were. of the abovementioned features, some take place together with the sense-power, namely those that pertain to sensitive apprehension, such as sense, imagination, and memory. Some take place through the sense-power, for instance those that pertain to the appetitive power, which is moved by the apprehension of sense-power. Of the others, which pertain even more clearly to the body, some are affections of the sense-power, namely sleep, which is a binding of sense-power, and wakefulness, which is its freeing; some are conditions of the sense-power, namely youth and old age, which have to do with whether the sense-power is in good condition or is weak; some are protections of and benefits to the sense-power, namely breathing, life, and health; and some are destructions and privations of it, namely death and sickness.
He says that the second premise, that sense is common to soul and body, is clear both by argument and without argument.
The argument is ready to hand. Since a sense-power is affected by something sensible, as was
shown in the book On the Soul,
and sensible things are bodily and material, what is affected
by the sensible is necessarily bodily.
Even without argument this is clear from experience, because if the bodily organs are disturbed, the operation of the sense-power is impeded; and if they are removed, the sense-power is completely removed as well.
CHAPTER 1
436B8–437A19
436b8 About sense and sensing—what it is and why this affection occurs in animals—something was said before in the discussions On the soul.
436b10 Any animal as animal necessarily has sense-power, for by this we determine that something is an animal or non-animal.
436b12 Taking each of them by itself, touch and taste accompany all necessarily, touch for the cause stated in the discussions On the soul, but taste because of food: for by this it distinguishes the pleasant (good-tasting) and unpleasant (bad-tasting) with respect to food, so as to avoid the latter, but pursue the former. And in general, flavor is the affection of the nutritive part of soul.
436b18 But the senses that go through what is external—such as smell, hearing, sight—are in those of them that advance. And they are in all that have them because of health, so that, pre-sensing, they might pursue food, but avoid what is bad and harmful.
437a1 And they are in those that have prudence for the sake of the “well”: for they announce many differences, from which there arises in them discernment of what can be contemplated and what can be done.
437a3 Of these, sight is better for what is necessary and of itself, but hearing for understanding and by accident.
437a5 For the power of sight announces many and many kinds of differences, because all bodies participate in color. Hence the common objects are also better perceived by this; I call size, shape, movement, and number “common.” But hearing announces only differences of sound, but to a few also those of voice.
437a11 But by accident hearing contributes a greater share to prudence. For discussion, being audible, is a cause of learning, not in itself but by accident; for it consists of words, and each of the words is a symbol. Hence of those deprived from birth of one of the two senses, the blind are wiser than deaf-mutes.
437a18 The power that each sense has has now been discussed.
Commentary
436b8 Having presented a prologue in which he has shown his intention, here the Philosopher begins to follow up his proposal.
First he determines about what pertains to the external sense-power. Second he determines about certain things pertaining to inner sensitive cognition, namely memory and recollection, where he says About memory and remembering (449b4), for the treatise On memory and recollection is part of the present book according to the Greeks.
On the first point he does three things. First he takes up some things that were said about the sense-power in the book On the soul and that are to be used as suppositions, as was said above. Second, he determines the truth that he intends about the workings of the senses and of sensible objects, where he says At present some inquire (Chapter 2, 437a19). Third, he solves certain difficulties about the foregoing, where he says But someone will raise an objection (Chapter 14, 445b3).
On the first point he does two things. First he states what was said about the sense-power in the book On the soul. Second he takes up some of these points, where he says Any animal as animal (436b 10).
Accordingly he first says that in the book on the soul, something was said about sense and
sensing—that is, about the sensitive power and its act. Two things were said about them,
namely what each of them is, and the cause why they occur in animals. He calls sensing an
“affection” (passio) because the action of sense cornes about in a being-affected (paciendo),
as was proved in On the Soul II.
Near the end of On the Soul II he showed what sense is and
why animals sense by the fact that animals are able to receive the forms of sensible things
without matter.
436b 10 Then, when he says Any animal as animal, he takes up three things that were said about sense in the book On the Soul. The first pertains to sense in general. The second pertains to the senses that are common to all animals; he takes this up where he says Taking each of them by itself (436bl2). The third pertains to the other senses, which are found in perfect animals; he takes this up where he says But the senses that go through what is external (436b 18).
Accordingly he first says that every animal, inasmuch as it is animal, necessarily has some sense-power: for the nature (ratio) of animal, by which it is distinguished from what is non-animal, consists in its being sensitive.
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The reason is this. An animal reaches the lowest level of knowing things, which surpass things that lack knowledge by being able to contain several beings in themselves, by which their power is shown to be more open and to extend to more things. And inasmuch as a knower has a more universal grasp of things, its power is more absolute, immaterial, and perfect. Now the sensitive power that is in animals is certainly open to what is outside, but only in the singular. Hence it also has an immateriality inasmuch as it is receptive of forms of sensible things without matter, but it has the lowest immateriality in the order of knowers, inasmuch as it can receive these forms only in a bodily organ.
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436b12 Then, when he says Taking each of them by itself he presents what pertains to the senses that are common and necessary to animals.
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On this point it must be considered that the senses that are common and necessary to every animal are those that apprehend what is necessary to an animal. Now there are two ways in which something sensible is necessary to an animal: in one way inasmuch as the animal is a mixed body, composed of the four elements, and thus there is necessary to it the required balance of hot and cold, moist and dry, and other such differences of mixed bodies; and something else is necessary to the animal inasmuch as its body is a living thing capable of being nourished, and thus suitable food is necessary to it. By the contraries of these an animal is destroyed. And although the first is necessary to every mixed body, and the second is also necessary to plants, an animal has something more than these in being able to have knowledge of what is necessary, for the reason already stated, according to the level of its nature. Accordingly, in order for it to apprehend what is necessary or harmful to it according to its nature (ratio) as a mixed body, it has the sense of touch, which apprehends the above-mentioned differences; and in order for it to apprehend suitable nourishment, the sense of taste is necessary to it, by which it apprehends what tastes good and bad, which are signs of suitable and unsuitable nourishment.
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This is why he says that touch and taste necessarily accompany all animals. Concerning touch, the cause was given in the book On the soul, namely that touch is cognitive of the things of which an animal is composed. But taste is necessary to an animal because of food, because by taste an animal distinguishes the pleasant and unpleasant, or good-tasting and badtasting, in food, so as to pursue one of these as suitable and avoid the other as harmful. And flavor as a whole is the affection of the nutritive part of soul—not that it is the object of the nutritive power, but that it is directed to the act of the nutritive power as its end, as was said.
But Alexander says in the commentary that in some manuscripts in Greek the text reads:
“flavor is the affection of the tasting part of the nutritive part of the soul.”
For flavor is
apprehended by taste, which is ordered to nourishment.
436b 18 Then when he says But the senses that go through what is external, he follows up on the senses that are only in perfect animals.
First he gives the general cause of these senses being in all animals of this kind. Second he gives the special cause of their being in the more perfect of them, where he says And they are in those that have prudence (437a1).
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On the first point it must be known that animals are called “perfect” in which there is not merely a sensitive part without forward movement, as in oysters, but which in addition have a moving part with respect to forward movement. And it must be considered that such animals surpass imperfect, that is, immobile animals as the latter surpass plants and other mixed bodies: for plants and inanimate bodies have no awareness of what is necessary to them; immobile animals have knowledge of what is necessary only inasmuch as it is immediately presented to them; but forward-moving animals also receive knowledge of what is necessary front a distance, and so they more closely approach intellectual knowledge, which is not confined to the here and now.
And just as in all animals taste is ordered to knowing the necessary pertaining to nourishment
inasmuch as it is immediately presented, so smell is ordered to knowing it front a distance as
well. For odor and flavor have an affinity, as will be said below,
and just as by flavor the
suitability of food taken in is known, so by odor the suitability of food at a distance is known.
But the other two senses, sight and hearing, are ordered to knowing from a distance
everything necessary or harmful to an animal, whether in its nature (ratio) as a mixed body or
in its nature as a living body capable of being nourished, for it is clear that by sight and
hearing animals avoid whatever is harmful and pursue what is healthy.
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And so he says that the senses that are actualized through external media, as was said in On
the Soul II,
namely smell, hearing, and sight, are in those among the animals that
advance—that is, move with forward movement—in all of them for one general cause,
namely because of health—that is, so that they might know what is necessary from a distance,
just as by taste and touch they know it when present. And he adds: so that, pre-sensing—that
is, sensing from a distance—they might pursue suitable food and avoid whatever is bad and
harmful. For instance, a sheep flees a wolf as something harmful, but a wolf pursues a sheep
that is seen, heard, or smelled, as suitable food.
437a1 Then, when he says And they are in those that have prudence, he gives another, specific cause why these senses are in some more perfect animals.
First he presents this cause. Second he compares the senses with refcrence to the causes mentioned, where he says Of these, sight is better (437a3).
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On the first point it must be considered that prudence is directive in what is to be done. Universal prudence is directive with respect to anything to be done whatsoever, and so it is in none of the animals except human beings, who have reason, which is able to know universals. But there are certain particular prudences in other animals for certain predetermined acts, for instance in the ant, which in summer gathers food on which it lives in winter.
Now the above-mentioned senses, but especially hearing and sight, are advantageous to
animals for particular prudences of this kind, and to human beings for universal prudence, in
order that something might be done well. But smell seems to be wholly subservient to the
need for nourishment, and not at all to prudence, and so this sense is extremely weak in all
those who have perfect prudence, as is said in the book On the soul.
He shows how the above-mentioned senses serve prudence by the fact that they show many
differences among things, froin which the human being goes on to discern what can be
contemplated and what can be done. For by sensible effects the human being is raised to
consideration of what is intelligible and universal; and also by what is sensible—that is, by
what he has heard and seen—he is instructed about what is to be done. Other animals do not
participate in any contemplation, although they do participate in action in a particular way, as
is said in Ethics X.
These two senses announce many differences because their objects are found in bodies as consequences of what is common to all bodies, both lower and higher. For color is a consequence of light and the transparent (dyaphanum), which lower bodies have in common with the heavenly body; and sound is a consequence of local movement, which is also found in both kinds of body. But odor is a consequence only of the mixed bodies by which an animal is naturally nourished.
437a3 Then, when he says But of these, sight is better, he compares sight and hearing with reference to the above-mentioned causes.
First he presents the comparison. Second he proves it, where he says For the power of sight (437a 5).
On the first point he says that sight surpasses hearing in two ways. In one way with respect to what is necessary, for instance in seeking food and avoiding what is harmful, things that are apprehended with more certainty by sight, which is altered by things themselves, than by hearing, which is altered by sounds, which are consequences of the movements of some things. in another way sight is also of itself superior to hearing, because it is more able to know, and able to know more ihings, than is hearing. But hearing surpasses sight inasmuch as it serves understanding, although this is by accident, as will be shown below.
437a5 Then he clarifies what he said, where he says For the power of sight announces.
First that sight is in itself better. Second that hearing is better accidentally, where he says But by accident hearing contributes (437a 11).
Accordingly he first says that sight is in itself better because the power of sight by its apprehension announces to us inany différences arriong things and among various kinds of things. This is because its object, which is the visible, is found in all bodies: for a thing becoines visible by the transparent being illuminated in actuality by a shining body, and the lower bodies have this in common with the higher ones. And so he says that all bodies participate in color, the higher as well as the lower ones, because in all bodies either there is color itself in its proper nature (ratio) in the case of bodies in which there is a bounded transparent; or there are at least the principles of color, which are the transparent and light. And so more things are manifested by sight than by hearing.
Also, the common sensibles are better known by this sense, because inasmuch as sight has a power of knowing that is more universal and extends to more things, it is more effective in knowing, because the more universal any power is, the more powerful it is. And those are called “common” sensibles that are known not by one sense only, as are the proper sensibles, but by several, for instance size, shape, inovement, and number. For the qualities that are the proper objects of the senses are forms in a continuum, and so the continuum itself, inasmuch as it is the subject of these qualities, must move the sense-power not accidentally, but as the per se and common subject of all sensible qualities. And all the so-called common sensibles do in some way pertain to the continuum: whether with respect to measurement of it, in the case of size; or with respect to division of it, in the case of number; or with respect to limitation of it, in the case of shape; or with respect to distance and nearness, in the case of motion.
But hearing announces to us only differences among sounds, which are not found in all
bodies, and are not expressive of the many diversities of things. But to a few animals hearing
does show differences of voice. Voice is sound projected with an imagining from an animal’s
mouth, as is said in On the soul II,
and so the voice of an animal as such naturally indicates
the animal’s inner feeling (passio), as the barking of dogs indicates their anger. Thus the more
perfect animals know one another’s inner feelings from voices, a knowledge that is not in
imperfect animals.
Therefore hearing of itself knows only differences among sounds, such as high and low and so on, or differences among voices inasmuch as they are indicative of varions feelings. And so the knowledge of hearing does not of itself extend to as many differences among things as does that of sight.
437a11 Then when he says But by accident hearing contributes, he shows that hearing is accidentally better for understanding.
He says that hearing contributes much te prudence. Here “prudence” is taken to rnean any
intellectual knowledge, not just “right reason about possible action,” as it is described in
Ethics VI.
But this is by accident, because discussion, which is audible, is a cause of
learning not of itself—that is, not by differences themselves among sounds—but by accident,
that is, inasmuch as words of which discussion (sermo)—that is, speech (locutio) is composed
are symbols—that is, signs—of meanings (intentiones) understood, and consequently of
things. Thus a teacher teaches a student inasmuch as, through discussion, he signifies what
his intellect con ceives to the student. And a human being can know more by learning from
someone else, for which hearing is useful, even though accidentally, than he can by
discovering for himself, for which sight is especially useful.
Hence it is that, among those deprived from birth of one of the two senses—that is, sight or hearing—the blind, who lack sight, are wiser than deaf-mutes, who lack hearing. He adds “mutes” because everyone who is deaf from birth is necessarily mute, for he cannot learn to form the signifying words that signify by convention, and so he stands in relation to the speech of the whole human race as one who has never heard a particular language stands in relation to that language. But it is not necessary, conversely, that every mute be deaf, for it can happen that someone is mute from some other cause, for instance obstruction of the tongue.
437al8 Finally, adding an epilogue, he concludes that the power that each sense has has been discussed.
CHAPTER 2
437A19–438A5
437a19 At presentsome inquire about the organs of the body in which these are actualized with reference to the elements of bodies. But not being able to adapt them to four, since there are five, they are concerned about the fifth.
437a22 But all of them have sight be made of fire, because they do not know the cause of a certain affection: when the eye is squeezed and moved, fire seems to shine. This happens in darkness, or when the eyelids are lowered, which also makes it dark.
437a26 But this presents another difficulty. For if something visible cannot escape the notice of one who is sensing and seeing, it will be necessary that the eye always be seeing fire. Why then does it not happen when it is at rest?
437a30 Now the cause of this—both for the objection and for the view that sight is made of fire—is to be understood as follows. Smooth things naturally shine in darkness, but they do not produce light; and the so-called black part and center of the eye is smooth. And what appears, appears to an eye that is moved because what happens is that what is one becomes as though it were two, and the speed of the movement makes it seem that what sees and what is seen are different. Hence it does not happen unless quickly.
437b5 This happens in darkness, for a smooth thing in darkness naturally shines, as do certain heads of fish, and the ink of the cuttle-fish. And when the eye is gently moved, it does not happen that what sees and what is seen seem simultaneously to be one and two. But in the other case, the eye itself sees itself, as it does in refraction.
437b10 If it were fire, as Empedocles says, and as is written in the Timaeus, and seeing took place by a light going out, the way it does from a lamp, why does sight not also see in darkness?
437b14 To say that in going ont it is “extinguished” in darkness is completetly foolish.
437b15 For what is “extinction” of light? What is hot and dry is extinguished by either moisture or cold, as can be seen in the case of the embers of a fire, and flame. But neither appears to be the case with light.
437b19 If it were the case, but the light escapes our notice because of “weakness,” it would have to be extinguished by day, and in water, and it would be more darkened where there is ice, for flame and burning bodies are affected in this way. But no such thing happens in this case.
437b23 Empedocles seems to think, as was said before, that seeing takes place by light going out. For he says:
As when someone contemplating going out on a winter night prepares a lamp, he kindles a light of burning fire in such a way as to block the force of all winds, for he deflects the breath of blowing winds. But the light breaks out: however farther it expands it illuminates with rays subdued by a covering— Likewise ancient light guarded in membranes—fine linens pours out around in a circle through the pupil, which will reveal a depth of water flowing around. But the light comes out, however farther it expands. Sometimes, then, he says that seeing is like this, but sometimes that it takes place by emanations from what is seen.
Commentary
437a19 After The Philosopher has summarized what is necessary for the present consideration of sensitive powers themselves, now he proceeds to his principal proposal in this book by applying the consideration of sense-powers to what is bodily.
First with respect to sense-organs. Second with respect to sensible objects, where he says Concerning sensible objects (Chapter 5, 439a6).
On the first point he does two things. He assigns sense-organs to elements, first disproving arguments of others; second determining what might more probably be the case, where he says If, then, what happens in these cases (Chapter 4, 438b 16).
On the first point he docs two things. First he touches in general on the way in which the Ancients assigned sense-organs to elements. Second he focuses specifically on the organ of sight, about which many were mistaken, where he says But all of them have sight be made of fire (437a22).
Accordingly he first says that previous philosophers asked, with reference to the elements of bodies, What are the kinds of bodily organs in which, and by which, the operations of the sense-powers are exercised?
They did so because, as was said in On the Soul I, they held that like is known by like, and
hence they held that the soul itself has the same nature as the principles of things, so that
thereby it might know all things, being as it were conformed to all things, since all things
share in the principles.
For the same reason they assigned sense-organs to elements of bodies, because all bodily things are known through sense-organs. But immediately one difficulty occurred to them: there are five senses and four elements. And so they looked for something to which they could assign the organ of the fifth sense.
Now between air and water there is an interniediary, denser than air but finer than water, which is called “smoke” or “vapor,” and some held that it is also a first principle, to which they assigned the organ of smell, since odor is perceived by means of a smoky evaporation. And they assigned the other four senses to the four elements: touch to earth, taste to water (since flavor is perceived by means of moisture), hearing to air, and sight to fire.
437a22 Then, when he says But all of them have sight be made of fire, he proceeds specifically to the organ of sight, which they assigned to fire.
First he disproves the cause they gave for their position. Second he disproves the position itself, where he says If it were fire (437b 10).
On the first point he does three things. First he presents the cause that moved some to assign the organ of sight to fire. Second he raises a difficulty, where he says But this presents another difficulty (437a26). Third he determines the truth about both points, where he says Now the cause of this (437a30).
Accordingly he first says that all who assign the organ of sight to fire do so because they do not know the cause of a certain affection that occurs in the eye: if the eye is pressed and forcefully moved, it seems that fire shines. if the eyelids are open, this happens only when the surroundings are dark; it also happens when the surroundings are bright if the eyelids are first closed, because thus one makes it dark to the closed eye. They thought that this affection is a clear sign that the organ of sight pertains to fire.
437a26 Then, when he says But this presents another difficulty, he raises a difficulty about the foregoing.
For it is clcar that a sense-power apprehends a sensible thing that is present, and hence that sight apprehends a visible thing that is present; and fire, because of its light, is something visible. Therefore, if fire is always present to sight, that is, to the organ of sight, since it exists in it, it seems that sight should always be seeing fire.
But this does not follow from the principles that Aristotle has established, for he holds that a
sense-power is in potentiality to a sensible thing, and that it must be altered by the thing
through a medium. According to him, then, a sensible thing placed on top of a sense-power is
not perceived, as is said in On the Soul II,
so that if the organ of sight were made of fire, for
this very reason sight would not see fire.
But according to the other philosophers sight and the other senses perceive sensible things inasmuch as they actually are of the same kind as—that is, like—the sensible things, because they have the same nature as the principles of things, as was said. According to them, then, just because the organ of sight is made of fire, it follows that it sees fire in the way described.
But then there remains the difficully that Aristotle here introduces: Why does an eye at rest not sec fire, as does an eye that is moved?
437a30 Then, when he says Now the cause of this, he gives the cause of the above-mentioned appearance, by which the difficulty raised is solved, and it is shown how foolish of them it was to think that sight is made of fire.
On this point it must be understood that smooth—that is, polished and clean—bodies have, from a property of their nature, a certain shine, one that does not occur in rough and uneven bodies because some parts rise above others and overshadow the latter. And although such bodies in a way shine in themselves, they do not have enough shine to be able to make a medium bright in actuality, as do the sun and such bodies.
Now it is clear that the center of the eye, which is called the black part of the eye, is as it were smooth and polished. Hence it has a shine by reason of its smoothness, not from the nature of fire, as the others thought. This already removes any need to assign the organ of sight to fire, since the cause of the brightness that appears can be attributed to something other than fire.
But whether it is caused by fire or the pupil’s smoothness, there remains a difficulty common to both positions: why an eye that is moved sees this shining, but an eye at rest does not.
So he gives the cause of this, and says that shining of this kind appears to an eye that is moved because what happens through the movement of the eye is that what is one becomes as though it were two. For the shining and seeing pupil is one and the same in subject: but inasmuch as it shines, it projects its shine outward; and inasmuch as it sees, it apprehends the shining by, as it were, receiving it from without.
When the eye is still, therefore, it emits the shine outward, and so sight does not receive the shine in such a way as to see it. But when it is quickly moved, its black part is brought, before the brightness fades, to the “external” place to which the pupil emitted its brightness. Thus the pupil, having been quickly brought to the second place, receives its own brightness as if from without, and so it seems that what sees and what is seen are different, although they are the same in subject. So this appearance of the shining does not happen unless the eye is quickly moved, because if it is moved slowly, the impression of the shining will fade from the “external” place the shining went to before the pupil gets there.
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But it seems that no speed of movement would suffice for this to happen. For however rapid local movement may be, it must be in time. But emission of shine at the presence of a shining body, and its cessation at the absence of it, occur instantaneously. Therefore it does not seem possible, however quickly the eye is moved, for the pupil to reach the “external” place before the shining, which came there from the pupil existing in the other place, ceases.
According to Alexander in the commentary, we must say in response that the pupil is a body, divisible into parts. Hence if the eye is quickly moved, when part of the pupil begins to reach the other place, the shining is still coming there from the rest of the body of the pupil that has not yet gotten to that place. This is why the pupil begins to see a shining that is, as it were, shining from elsewhere. A sign of this is that the shining does not seem to fade: rather, when it passes, the sight of it ceases abruptly.
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437b5 He also gives the reason why this kind of operation happens in darkness and not in light, namely because the shining of smooth bodies is so small that it is obscured by great brightness, although it is seen in darkness. This also happens with other things that have a small amount of light, and for this reason are seen in darkness but net in light, for instance certain heads of fish, and the dark fluid of the fish called the cuttle-fish. He adds that if the eye is gently—that is, slowly—moved, the above-mentioned appearance does not happen by what sees and what is seen seeming simultaneously to be one and two, as was said. But in the other case—that is, when the eye is quickly moved—then the eye sees itself being as it were affected by itself in its other position. This also happens in “refraction”—that is, reflection—for instance when an eye sees itself in a mirror from which, as from without, the form of the eye returns to the eye itself by way of reflection, just as, in the above-mentioned appearance the shining of the eye returns to the eye itself, as was said.
437b 10 Then when he says If it were fire, he proceeds to disprove the position itself: first inasmuch as those philosophers assigned sight to fire; second inasmuch as they held that sight sees by extromission, where he says It is altogether irrational (Chapter 3, 43 8a25).
On the first point he does three things. He presents first the opinion of Plato; second the opinion of Empedocles, where he says Empedocles seems to think (437b23); and third the opinion of Democritus, where he says Democritus says correctly (Chapter 3, 438a5) .
On the first point he does two things. First he raises an objection against Plato. Second he disproves Plato’s response, where he says To say that in going out (437b 14).
Concerning the first point it must be known that Empedocles, and Plato in the Timaeus, agreed on two things: one is that the organ of sight pertains to fire; the second is that vision occurs by a light going out from the eye as from a lamp. From these two positions the Philosopher concludes that sight should see in darkness, just as it does in light: for light can be emitted from a lamp to light up the medium in the dark; and so, if the eye saw by emission of light, it would follow that the eye should also be able to see in the dark.
437bl4 Then, when he says To say that in going out, he disproves the response of Plato, who says in the Timaeus that when light goes out from the eye, if it encounters light in the medium it is preserved by it as by something like itself, and because of this vision occurs; but if it does not encounter light, but darkness, then because of the unlikeness of darkness to light, the light going out from the eye is “extinguished,” and so the eye does not see. But Aristotle says that to give this cause is foolish.
437bl5 And he proves this where he says For what is “extinction” of light?
For no reason can be given why the light of the eye is “extinguished” by darkness. The
Platonists said that there are three species of fire, namely light, flame, and ember.
Since fire
is naturally hot and dry, it is extinguished by either cold or moisture, and this clearly happens
in the case of embers and flame. But neither is a cause of extinction in the case of light, for it
is destroyed neither by cold nor by moisture. Therefore it is incorrect to say that light is
extinguished in the way fire is.
But Alexander says in the commentary that there is another reading, as follows:
437bl5 ... as is seen in fire in embers and flame. But neither seems to belong to darkness. For it is neither moisture nor cold by which the “extinction “ occurs.
And on this reading Aristotle’s argument seems to be more to the point: the fire-light that appears in embers and flames is found to be extinguished by cold and moisture; but darkness is neither something cold nor something moist; therefore the fire-light that goes out from the eye cannot be extinguished by darkness.
437b19 Someone might say that the fire-light going out from the eye is not “extinguished” in darkness, but that, because it is not “strengthened” by external light, and so is weak, it escapes our notice, and that this is why vision does not occur.
But Aristotle disproves this where he says If it were the case.
On this point it must be known that fire-light is “extinguished” or darkened in two ways: in one way with respect to a property of light, namely that a little light is extinguished by the presence of a greater light; in another way with respect to a property of fire, which is extinguished in water.
Accordingly if the weak light going out front the eye were made of fire, it would have to be extinguished in daylight, because of the greater brightness; and in water, because of its contrariety to fire; and the light of the visual power would be even more darkened where there is ice, for we see that this is what happens in the case of flame and burning bodies. But it does not happen in the case of sight, and so it is clear that the abovementioned response is foolish.
437b23 Then, when he says Empedocles seems to think, he relates the opinion of Empedocles, the disproof of which has already been touched on.
He says that Empedocles seems to think, as was said, that vision occurs by light going out.
And he gives the words of Empedocles, which were composed in meter. Empedocles said that what happens in vision is like when someone thinking of going out along a road on a winter night—that is, when wind is blowing—prepares a lamp. He kindles a light of burning fire, and to block the force of all winds he puts the light kindled in a lantern, and by this means he deflects the blowing of breathing winds—that is, he prevents their blowing from reaching the light of the fire. But the light contained within goes out, and however farther outward it expands, it illuminates the air more, but in such a way that the rays going out are subdued—that is, weakened—by a covering on the lamp, for instance skin or some such thing; for the air is not as brightly illuminated by the lamp as it would be by unshielded fire.
And he says that something similar happens in the eye, in which ancient light—that is, light there since the eye’s formation—is guarded—that is, safely preserved—for sensing, in membranes—that is, corneas of the eye—through which, as if through fine linens, light pours out around in all directions through the pupil. These corneas reveal, by the rays emitted through them, a depth of water flowing around the fire kindled in the pupil, water for nourishing, or rather tempering, the fire gathered in the depth. And so the light reaches out, however farther it expands, starting from inside.
Alternatively, his mention of “around in a circle” should be understood with reference to the roundness of the pupil.
It should be noted that he said, significantly, “with rays subdued by a covering,” to indicate the reason why a thing is not seen in darkness, namely that the light going out is weakened by passing through the above-mentioned coverings, so that it cannot completely illuminate the air.
Having presented the words of Empedocles, he adds that sometimes he said that vision occurs by emission of light, as was said, but sometimes he said that vision occurs by certain bodies emanating from visible things and coming to sight. And perhaps his opinion was that the two are united for vision.
CHAPTER 3
438A5-B2
438a5 Democritus says correctly that it is water, but not correctly that he thought that the appearance is the seeing itself. For this occurs because the eye is smooth. And it is not in that, but in what is doing the seeing. For the affection is a reflection. But it seems that it was not yet clear to him about appearances and reflection.
438a10 But it is inconsistent that it also did not occur to him to wonder why only the eye sees, and none of the other things in which “idols “ appear.
438a12 For it is indeed true that sight is made of water, but seeing does not occur according as it is water, but according as it is transparent, which is something common to it and air. But water is more preservable than air and denser, which is why the pupil and eye are made of water.
438a17 This is manifested in the very workings. For when eyes are destroyed, water can be seen flowing out. And in completely new-formed ones, there is extreme cold and brightness. And in those that have blood, the white of the eye is fat and thick, to keep the moisture unfrozen; and so the eye is the part of the body that feels cold least, for no one has ever felt cold inside the eyelids. The eyes of bloodless animals are made of hard skin, and this provides protection.
438a25 It is altogether irrational that sight should see by something going out, whether it extends all the way to the stars, or, as some say, it goes only so far and “coalesces.”
438a27 For in the latter case it is better for it to be united at the beginning, that is, in the eye.
438a29 But this is also foolish. For what is it for light to be “united” to light? Or how is it possible, since not just anything is united with anything? And how is the inner light united with the outer, since the membrane is between?
Commentary
438a5 After the opinions of Plato and Empedocles, here, in the third place, The Philosopher follows up the opinion of Democritus.
On this point he does thrce things. First he shows what Democritus said correctly and what he said incorrectly. Second he follows up what he said incorrectly, where he says But it is inconsistent (438a10). Third he follows up what he said correctly, where he says For it is indeed true that sight is made of water (438al2).
Accordingly he first says that Democritus spoke correctly in assigning sight to water, but he spoke incorrectly in saying he thought that vision is nothing but the appearance in the pupil of the thing seen. For such an appearance occurs in the pupil because of the bodily disposition of the eye, that is, because the eye is smooth, that is, polished and clean, as it were. So it is clear that seeing itself is not located in the appearance of this form in the eye, but in what is doing the seeing, that is, in what has the power of sight: for the eye is a seeing thing not because it is smooth, but because it has the power of sight. For that affection—the appearing of the form of the thing seen in the eye—is a reflection; that is, it is caused by the reflection or rebound of the form from a polished body.
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We see something like this happen in a mirror also. For when the alteration of the transparent caused by a visible body reaches a body that is net transparent, the alteration can go no further, but is somehow turned back, like a ball thrown at a wall and bounced back, and because of this rebound the form of the thing seen goes back in the opposite direction. Thus in a mirror one can see oneself, or even some other thing not directly presented to ones sight.
This takes place only if two things coincide. One is that the body be smooth on its surface, and therefore somewhat bright, as was explained above; the form reflected in it is manifested by this moderate brightness. The other is that the body be terminated within at some point so that the above-mentioned alteration does not go beyond; thus we see that this kind of appearance does net occur, unless glass is covered with lead or something similar to block its transparency, so that the alteration does not go beyond.
Now both of these coincide in the eye: it is moderately bright because of its smoothness, as was established above, and it has something in its depth that terminates its transparency. So it is clear that this event of the form of the thing scen appearing in the eye happens merely because of reflection, which is a bodily affection caused by the determinate disposition of a body.
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But it was not yet clear to Democritus about these reflections and about the forms that appear in mirroring bodies because of reflection. Vision itself, according to the truth of the matter, is not a bodily affection: rather, its principal cause is a power of soul. But Democritus held that soul is something bodily, and so it is no wonder that he called an operaion of soul nothing but a bodily affection.
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It should be known, however, that the above-mentioned appearance is a cause of vision with respect to initial reception of the form. For vision is an act of soul only through a bodily organ, and so it is no wonder that it has a cause from the point of view of a bodily affection, but in such a way that the bodily affection is not the same thing as the vision: rather, it is a cause of it with respect to the initial “impact,” if I may so call it, of the visible form on the eye. The subsequent reflection conributes nothing to the eye’s seeing of the thing seen through the form appearing in it, but rather contributes to the form’s being able to appear to someone else; thus the eye that sees the thing by means of the form that appears in it does not see this form itself.
438a10 Then, when he says But it is inconsistent, he follows up what Democritus said incorrectly.
He says that since Democritus held that vision is nothing but the above-mentioned appearance, it seems very inconsistent that the following difficulty did not occur to him: Why do other bodies in which forms, which he called “idols”—of visible things appear as in a mirror not see, but only the eye? From this it is clear that the above-mentioned appearing is not the whole essence (ratio) of vision, but that there is something else in the eye that causes vision, namely the power of sight.
438a12 Then, when he says For it is indeed true that sight is made of water, he follows up what Democritus said correctly.
First he presents the truth. Second he clarifies it by signs, where he says This is manifested (43 8a 17).
Accordingly he first says that what Democritus said in assigning the organ of sight to water is
true. However, it niust be known that vision is assigned to water not according as it is water,
but by reason of transparency, which water and air have in common: for a visible object is
something that moves the transparent, as is said in the book On the Soul.
However, vision is
assigned to water rather than to air for two reasons. First, water can be preserved better than
air (air is easily dispersed), and so it is more suitable for the preservation of sight than is air,
and nature always does what is better. Second, water is denser than air, and by reason of its
density it allows the form of a thing seen to appear in it by reflection, which is proper to the
organ of sight. What is proper to the medium of sight is to be transparent, which is common
to air and water. So he concludes that the eye and pupil are to be assigned to water rather than
to air.
The heavenly body is also transparent, but because it does not enter into the composition of the human body, he passes over it here.
438a17 Then, when he says This is manifested, he shows that the organ of sight is made of water by three signs that are manifested in the very workings.
The first is that if the eyes are destroyed, there visibly appears water flowing out of them.
The second is that the new-formed eyes of embryos—eyes that, as it were, still retain much of the power (virtus) of their origin—have abundant cold and brightness, both of which are connatural to water.
The third sign is that in animals that have blood, in which there is the possibility of generating, so to speak, fat from the blood, the pupil is surrounded by the white of the eye, which has fatness and oiliness so that its heat will keep the water-moisture of the pupil from freezing, which would diminish the transparency of the water, and thus impede vision. And so, by reason of the above-mentioned fat, the eye, because of its heat, does not freeze: for no one has ever suffered cold in the whole of what is contained inside the eyelids. In animals that are bloodless, in which there is no fat, nature made eyes of hard skin to protect the water-moisture that is in the pupil.
438a25 Then, when he says it is altogether irrational, bc goes on to disprove what some held, namely that vision occurs by extromission, which was the reason for their assigning sight to fire. Thus, once the latter is eliminated, the former will be too.
On this point he does two things. First he presents two opinions of those who held that we see by extromission. Second he disproves the second opinion, where he says For in the latter case (438a27).
Accordingly he first says that it seems irrational that sight should see by something going out from it, which was held to occur in two ways.
In one way such that what goes out from the eye extends all the way to the thing seen, from which it would follow that even when we see the stars, what goes out from sight extends all the way to the stars.
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This involves an obvious impossibility. Since “going out” pertains only to bodies, it would follow that some body going out from the eye would reach all the way to the stars, which is clearly illogical, for many reasons.
First because it would follow that there are several bodies in the same place, both because what goes out from the eye would be in the same place as the air, and because these things going out from eyes would have to be multiplied in the same medium according to multiplicity of those who are seeing through the same medium.
Second because any projection of a body is stronger at the beginning but weaker at the end, which is why flame proceeding from a burning body tends towards an apex. But here the contrary happens, for the mathematicians, whose position this is, say that the apex of the body going out from the eye is inside the eye and the base at the thing seen.
Third because the size of an eye is insufficient for a body going out from it to be big enough to reach all the way to the stars, however much the body rnight be rarefied, for there is a limit to the rarefaction of natural bodies; besides, the more rarefied it became, the more easily it would be destroyed.
Again, the body emitted from the eye would have to be either air or fire. There is no need for air to be emitted from the eye because it is abundant outside the eye. And if it were fire we would also see at night; on the other hand, we would not be able to sec through the medium of water; and we would only be able to see upwards, where the movement of fire tends.
But it cannot be said that the bodily thing that goes out from the eye is light, because light is not a body, as was proved in the book On the soul.
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The other opinion is that of Plato, who held that light going out from the eye does not go all the way to the thing seen, but only so far, that is, some determinate distance, namely to where it “coalesces” with the external light; and that vision occurs by reason of this coalescence, as was said before.
438a27 Then, when he says For in the latter case, he passes over the first opinion as clearly unreasonable, and disproves the second in two ways.
First because it posits something uselessly and unnecessarily, which is just what he says: that it would be better to say that the inner light is united with the outer at the surface of the eye itself rather than outside at some distance. This is because if there is no outer light in the intermediate space, the inner light will be extinguislied by darkness according to Plato’s opinion, as was said above. But if light reaches all the way to the eye, it is better for the two to be united immediately, because what can occur without a medium is better than what occurs through a medium, since it is better for sornething to occur by means of fewer things than more.
438a29 Second, where he says But this is also foolish, he disproves the union of inner light with outer even on the supposition that it occurs at the beginning, i.e. in the eye itself. He docs this in three ways.
First because “being united and separated” is proper to bodies, each of which has subsistence
per se, but not to qualities, which exist only in a subject. Hence, since light is not a body but
an accident, it is meaningless to say that light is “united” to light, unless what is meant is that
a luminous body is united to a luminous body. Howver, it is possible for light to be
intensified in the air by multiplication of luminous bodies, as heat is imensified by increase in
the cause of heat, although this is not by addition, as is clear from Physics IV.
Second he disproves the point as follows: even granted that both lights are bodies, it would still not be possible for them to be united, since they are not of the same nature. For not just any body is naturally united with just any body, but only those that are in some way homogenous.
Third, since an intervening body, namely the membrane—that is, the cornea of the eye—comes between the inner and the enter light, there cannot be a union of the two lights.
CHAPTER 4
43SB2-439A5
438b2 That it is impossible to see without light was said elsewhere. But whether it is light or air that is between the thing seen and the eye, the movement through it causes seeing.
438b5 It is reasonable that what is inside be made of water, for water is transparent. And it seems that, as what is outside is not without light, so also what is inside. Therefore it must be transparent. Therefore it is necessarily water, because it is not air
438b8 For the soul, or the sensitive part of soul, is net at the limit of the eye, but clearly inside. Hence the inside of the eye needs to be transparent and receptive of light.
438b11 This is also clear from what happens. For when some are wounded in war about the temples in such a way that the passages of the eye are cut off, they experience a darkening as when a lamp is extinguished, because the transparent thing called the pupil is, like a torch, cut off.
438bl6 If then, what happens in these cases is as we have said, it is clear that, if one must, following this method, attribute and assign each one of the sensitive parts to one of the elements, one should think that eyesight is of water, what is perceptive of sounds is of air, and smelling is of fire.
438b21 For what smelling is in actuality the olfactory part is in poientiality. For a sensible object makes a sense-power act, and so the latter necessarily exists first in potentiality. But odor is smoky evaporation. But smoky evaporation is from fire.
438b25 For this reason the proper sensitive part of smell is in a place around the brain: for the potentially hot is the matter of what is cold.
438b27 And the generation of the eye also has the same mode: for it stems from the brain, and the brain is coldest and moistest of all parts of the body.
438b30 But the tactile part is of earth, and the tasting part is a kind of touch.
439a1 And so the sensitive part for these, namely taste and touch, is near the heart: for the heart is opposite the brain, and is the warmest of the parts.
439a4 Let it be determined in this way about the sensitive parts of the body.
Commentary
438b2 After the Philosopher has disproved the opinion of those who hold that vision occurs by extromission, here he determines the truth.
On this point he does three things. First he makes clear how vision occurs according to his own thought. Second, on this basis, he gives the cause of something mentioned above concerning the organ of sight where he says It is reasonable (438b5). Third he shows the cause by sign, where he says This is also clear (438b11).
Accordingly he first takes up something that was said in the book On the Soul, that it is
impossible to see without light.
For because vision occurss through a medium that is
transparent, vision requires light, which makes a body be transparent in actuality, as was said
in the book On the Soul.
And so, whether the medium that is between the thing seen and the
eye is air that is illuminaied in actuality, or whether it is light—light existing not in itself,
since it is not a body, but in something else that is a body, such as glass or water—the
movement that occurs through this medium causes vision.
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This movement should not be taken to be local movement, as if, as Democritus and Empedocles held, it were a movement of bodies emanating from the thing seen to the eye, because then it would follow that the bodies that are seen would be reduced by this emanation until they were totally worn away. It would also follow that the eye would be injured by the continuons striking of these bodies. Again, it would not be possible for a whole body to be seen by anyone, but only as much as could be taken in by the pupil.
Rather, this is “movement” according to alleration: the alteration is a movement towards a form that is a quality of the thing seen. inasmuch as it is bright in actuality, the medium is in potentiality to this form; the medium is an unbounded transparent (color is a quality of a bounded transparent, as will be said below), and what is unbounded is related to what is bounded as potentiality to actuality, for form is a boundary of matter.
Now because of the different nature (ratio) of the transparent in a transparent medium, the medium receives the form of a color in a mode that is different from the mode in which it exists in the colored body, where there is a bounded transparent, as will be said below; for actualities are in receivers according to the mode of the latter. Thus color is in a colored body as a quality complete in its natural being, but it is in the medium incompletely, according to an intentional being. Otherwise something black and something white could not be seen through the same medium. For whiteness and blackness cannot simultaneously be in the same thing as forms complete in their natural being, but with respect to the above-mentioned incomplete being they do exist in the same thing: for this mode of being, because of its imperfection, approaches the mode by which something exists in something else in potentiality, and opposites are simultaneously in potentiality in the same thing.
438b5 Then, when he says It is reasonable, in keeping with what was said he gives the cause of the necessity of assigning sight to water, which he showed above only by signs.
He says that, because what causes vision is the alteration of a medium made bright by the body seen, it is reasonable that what is inside the pupil, which is the organ of sight, be made of water: for water is one of the transparent things. But the external medium is a transparent thing that has been illuminated, and nothing can be seen without this illuminaition: so the light must also be inside the eye. And because there can be light only in what is transparent, there must also be something transparent inside the eye. It is not the heavenly body, because this does not enter into the composition of the human body: and so it is necessarily water which is casier to preserve and thicker than air, as was said.
438b8 Then, when he says For the soul, he makes clear why light within is required for seeing.
If the power of sight were on the outer surface of the eye, the light of the external transparent, through which the alteration by the color reaches the outer surface of the pupil, would alone suffice for seeing. But the soul, or the sensitive part of soul, is not on the outer surface of the eye, but inside.
It should be noted that he significantly adds “or sensitive part of soul.” Since the soul is the form both of the whole body and of its individual parts, it is necessarily in the whole body and in each of its parts, because a form is necessarily in that of which it is the form. Now the sensitive part of the soul is called the sensitive “power,” being the principle of sensitive operation; and the principle of an operation of soul that is exercised by means of the body must be in a determinate part of the body. Thus the principle of sight is within, near the brain, where two nerves coming from the eyes meet.
Therefore, inside the eye there must be something transparent, receptive of light, so that there is uniform alteration from the thing seen all the way to the principle of sight.
438b11 Then, when he says This is also clear, he makes clear what he said by means of a sign, namely something that happens in some who are wounded around the temples in battle: when the passages that connect the pupil to the principle of sight are cut off, a darkening suddenly occurs through loss of sight, as if a lamp were extinguished. The pupil is like a torch lit up by an external light; thus, when the passages connecting the pupils to the principle of sight are cut off, the light of this torch cannot reach all the way to the principle of sight, and so sight is darkened.
438b16 Then, when he says If, then, what happens in these cases, having eliminated false opinions of others, he procceds to the principal proposal.
First with respect to the organs of the non-necessary senses. Second with respect to the organs of the necessary senses, where he says But the tactile part (438b30).
On the first point he does two things. First he coordinates sense-organs with elements. Second he clarifies what he said, where he says For what smelling is in actuality (438b21).
On the first point it must be considered that it was not in keeping with the thought of Arisiotle
to assign the sense-organs to elements, as is clear in the book On the Soul.
But because other
philosophers did assign the sense-organs to the four elements, therefore, condescending Io
them, as it were, in this matter, he says that, presupposing what was said about sight, if one
must, following what others say, assign each of the sensitive parts—that is, sense-organs—to
one of the elements, as others do, one should think that eyesight is to be assigned to water,
what is perceptive of sounds to air, and smelling to fire.
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But this seems to be contrary to what was said in on the Soul: “The pupil is of water, hearing
of air, and smell is of either of these; but fire either belongs to none or is common to all.”
In response to thisbemust be said that what the sense of smell is can be taken in two ways: in
one way according to potentiality, and thus the organ itself of smell is made either of air or of
water, as is said in On the soul III;
in another way according to actuality, and thus what is
said here is true, as he himself will prove. Thus it is significant that he did not say that the
“sense of smell” is made of fire, as be did say that “the part perceptive of sounds” is made of
air and “eyesight” is made of fire. Rather he says that “smelling” is made of fire. For “sense
of smell” refers to the potentiality, but “smelling” to the actuality.
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438b21 Then, when he says For what smelling is in actuality, he proves what he has said about the organ of smell.
On this point he does three things. First he shows that the act of smelling in actuality is related to fire. Second bc concludes to what should be the quality and place of the organ of smell, which is the act of smelling in potentiality, where he says For this reason (438b25). Third be shows a resemblance of the organ of smell to the organ of sight, where he says And the generation of the eye (438b27).
Accordingly he first says that the olfactory part—that is, the organ that lias power to smell—must be in potentiality what actual smelling is in actuality. He clarifies this as follows: a sensible object makes a sense-power actthat is, be in actuality, or again, operate. But the sensitive part must be in potentiality the sensible object: otherwise it would not be affected by it. Hence it remains that the sensitive part is in potentiality what sensing is in actuality.
Now it is clear that odor is smoky evaporation. Not that “smoky evaporation” is the very
essence of odor, for this was disproved in On the Soul it on the grounds that odor spreads
farther than does smoky evaporation.
Rather this is said because smoky evaporation is a
cause of odor being perceived. But smoky evaporation comes front fire, or whatever is hot.
Therefore the sense of smell is brought to actuality by heat, which is in fire as in its principle.
This is why flowers have stronger odor in hot times and places.
438b25 Then, when he says For this reason, he concludes from the foregoing that the organ of smell should be in a place near the brain.
For the organ of smell is, in potentiality, odor in actuality; odor in acuality exists by heat or fire; therefore the organ of smell must be hot in potentiality. But the potentially hot is the matter of what is cold, because the matter of contraries is the same, and it cannot be in potentiality to one of them without being in actuality under the other, either perfectly or, when it is under the form of an intermediate, imperfectly. So the substance of the organ of smell must be something that is cold and moist in actuality, and this is especially the case around the brain. Hence the organ of smell is around the brain.
438b27 Then, when he says And the generation of the eye, he shows a point of agreement between the organ of smell and the organ of sight.
He says that the generation of the eye also has the same mode, inasmuch as it stems front the brain. It does so because the brain is the coldest and moistest of all parts of the body, and so it has the nature of water, which is naturally cold and moist. Thus the brain fits both with the organ of smell, which should be hot in potentiality, and with the organ of sight, which should be made of water.
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But then it scenis that Plato fittingly assigned sight to fire, as Aristotle here assigns smell to fire.
To this it must be said that the organ of smell is made of water inasmuch as water is potentially hot, heat being a feature of fire. But the organ of sight is made of water inasmuch as water is transparent, and consequently luminous in potentiality.
But because fire is also luminous in actuality, as well as hot, someone might then say that sight is fittingly assigned to fire.
To this it must be said that, just as Aristotle assigned smell to fire, so nothing prevents sight from being assigned to fire—not according to the proper qualities of fire, which are heat and dryness, but according as fire is luminous in actuality.
The other philosophers seem to have focused on this, basing their argument on the shining that appears when the eye is moved. Aristotle disproved their opinion in this regard not because they held that sight in actuality is fire, which in a way would be true, inasmuch as sight in actuality does not occur without light, as the act of smelling in actuality does not occur without heat; rather, he did so because they held that the organ of sight is luminous in actuality, holding as they did that sight occors not by a taking in, but by an extromission.
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438b30 Then, when he says But the tactile part, he makes a determination about the organs of the necessary senses.
First he shows the element to which they are to be assigned. Second he shows the place where they are situated, where he says And so the sensitive part (439a1).
Accordingly he first says that the organ of touch is assigned to earth, and similarly the organ
of taste, which is a kind of touch, as was said in On the soul II.
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Now this is not to be taken to mean that the organ of touch or taste is simply made of earth,
for we do not perceive by means of hair, which contains even more earth. It is rather that, as
is said in On the Soul III, carth is mixed into the organs of these senses to the greatest
degree.
With respect to the organ of touch, the reason, as is said in On the Soul II, is this.
In order
for the organ of touch to be in potentiality to conirary tangible qualities, it has to have a
composition that is intermediate. Therefore, it has to have the greatest amount of earth, which
has less active power than do the other elements.
With respect to the organ of taste, the reason is clear. The organ of smell has to contain water in order to be in potentiality the hot thing without which there is no smelling in actuality. Similarly, the organ of taste has to contain earth in order to be in potentiality the moist thing without which there is no tasting in actuality.
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439a1 Then, when he says And so the sensitive part, he shows where the organ of taste and touch is based.
He says that it is near the heart, and be gives the reason, namely that the heart is opposite the brain with respect to position and quality. As the brain is the coolest part of the body, the heart is the warmest of all the parts of the body. For this reason they are placed in opposition to one another in order for the heart’s heat to be moderated by the brain’s coolness.
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This is why those who have heads that are small in proportion to their other parts are impetuous, as if the heat from the heart were net being pushed back down enough by the brain. Conversely, those who have unusually big heads are very slow and dull, as if the heat from the heart were being impeded by the size of the brain.
Since the organ of touch is made of earth, it must be in the body’s warmest place as in its principle, so that by the heart’s heat the coolness of the earth can be brought to a moderate temperature. This does not prevent an animal from perceiving by means of touch through the whole of its body, because as other senses perceive through an external medium, touch and taste perceive through an internal medium, namely flesh. And just as the principle of sight is not on the surface of the eye, but within, the principle of touch is also within, near the heart, a sign of which is that the most painful wounds are those around the heart.
But it cannot be said that there are two sensitive principles in an animal, one near the brain,
where the visual, olfactory, auditory principle is established, and one near the heart, where the
tactile and gustatory principle is established. The sensitive principle is primarily in the heart,
which is also where the source of heat is located in the body of an animal, because nothing is
sensitive without heat, as is said in On the Soul.
The sensitive power flows front the heart to
the brain, and front there it proceeds to the organs of three senses, sight, hearing, and smell.
But touch and taste are relayed to the heart itself through a medium united to the body, as was
said.
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439a4 Finally, by way of an epilogue, he says let it be determined in this way about the sensitive parts of the body—that is, as was done above.
CHAPTER 5
439A6–B14
439a6 Concerning sensible objects, in relation to each sensitive part—I mean, for instance, color and sound and odor and taste and touch—it was said in a gencral way in the discussions On the soul what their action is; and what it is to operate in relation to each sensitive part. But it is necessary to say what each of them is; that is, it must be considered what color is, what sound is, what odor is, what flavor is, and similarly also concerning touch. And first concerning color.
439a12 Each, then, is spoken of in two ways: on one hand in actuality, on the other in potentiality. Accordingly, what color in actuality is, and sound, how they are the same as or other than the sense-powers in actuality, namely seeing and hearing, has been said in the discussions On the soul. But let us now say what each of them is that it should cause sensing and actuality.
439a18 Accordingly, as was said about light in those discussions, it is the color of the transparent accidentally. For when something lit up exists in the transparent, the presence is light, and the privation darkness.
439a21 But what we call the transparent is not a property of air or water or any of the bodies mentioned, but is a common nature and power. It is not separate, but it is present in these and in other bodies, in some to a greater extent, in some to a lesser.
439a25 Therefore, as there is necessarily a limit of bodies, so there also is of this. Now the nature of light is in the unlimited transparent. But it is obvious ihat there will be a limit of the transparent that is in bodies, and that this is color is clear from what happens: for color is on the limit or is the limit. Hence the Pythagoreans called color an “epiphany”; for it is on the limit of a body, but it is not the limit of the body.
439a33 Now one must think that it is the same nature that is colored from without and intrinsically. Air and water appear as colored things, for the dawn is such a thing. But in this case, because it is in something indeterminate, neither the air nor the sea has the same color to those who approach close up and from afar. But in bodies, unless something containing makes a change, there is a determinate fantasia of color. Therefore it is clear that both in the former and in the latter it is the same thing that is receptive of color. Therefore the transparent, according as it exists in bodies—and it exists in all of them, to a greater or lesser extent—is what causes colors to be participated in. But because color is on the limit, it will be a limit of this.
439bl 1 Therefore color will be the limit of the transparent in a determinate body.
439b12 And in transparent things such as water and any other such thing, and in whatever seems to have a color of its own—in all these it is likewise at the limit.
Commentary
439a6 After The Philosopher has applied the consideration about sense-powers of animals to sense-organs, here he applies it to sensible objects themselves.
First be states his intention. Second he carries out his proposal, where he says Accordingly, as was said about light (439a18).
On the first point be does two things. First he proposes his intention. Second be clarifies what be said, where he says Each, then, is spoken of in two ways (439a12).
Accordingly be first speaks of proper sensible objects, those perceived in relation to each sensitive part, that is, each individual sense-organ, which he saysto distinguish them from common sensibles. The proper sensibles are color, sound, and odor, which are sensed through sight, hearing, and smell; and taste and touch—that is, the objects of these senses. He says that it was said in On the soul in a general way both how these act on a sense-power and the nature of the sense-power’s operation in relat