Aristotle

by Various Works [lit]

  soul is to seek in the case of each of its forms for the most

  appropriate definition.

  4

  It is necessary for the student of these forms of soul first to find

  a definition of each, expressive of what it is, and then to

  investigate its derivative properties, c. But if we are to express

  what each is, viz. what the thinking power is, or the perceptive, or

  the nutritive, we must go farther back and first give an account of

  thinking or perceiving, for in the order of investigation the question

  of what an agent does precedes the question, what enables it to do

  what it does. If this is correct, we must on the same ground go yet

  another step farther back and have some clear view of the objects of

  each; thus we must start with these objects, e.g. with food, with what

  is perceptible, or with what is intelligible.

  It follows that first of all we must treat of nutrition and

  reproduction, for the nutritive soul is found along with all the

  others and is the most primitive and widely distributed power of soul,

  being indeed that one in virtue of which all are said to have life.

  The acts in which it manifests itself are reproduction and the use

  of food-reproduction, I say, because for any living thing that has

  reached its normal development and which is unmutilated, and whose

  mode of generation is not spontaneous, the most natural act is the

  production of another like itself, an animal producing an animal, a

  plant a plant, in order that, as far as its nature allows, it may

  partake in the eternal and divine. That is the goal towards which

  all things strive, that for the sake of which they do whatsoever their

  nature renders possible. The phrase 'for the sake of which' is

  ambiguous; it may mean either (a) the end to achieve which, or (b) the

  being in whose interest, the act is done. Since then no living thing

  is able to partake in what is eternal and divine by uninterrupted

  continuance (for nothing perishable can for ever remain one and the

  same), it tries to achieve that end in the only way possible to it,

  and success is possible in varying degrees; so it remains not indeed

  as the self-same individual but continues its existence in something

  like itself-not numerically but specifically one.

  The soul is the cause or source of the living body. The terms

  cause and source have many senses. But the soul is the cause of its

  body alike in all three senses which we explicitly recognize. It is

  (a) the source or origin of movement, it is (b) the end, it is (c) the

  essence of the whole living body.

  That it is the last, is clear; for in everything the essence is

  identical with the ground of its being, and here, in the case of

  living things, their being is to live, and of their being and their

  living the soul in them is the cause or source. Further, the actuality

  of whatever is potential is identical with its formulable essence.

  It is manifest that the soul is also the final cause of its body.

  For Nature, like mind, always does whatever it does for the sake of

  something, which something is its end. To that something corresponds

  in the case of animals the soul and in this it follows the order of

  nature; all natural bodies are organs of the soul. This is true of

  those that enter into the constitution of plants as well as of those

  which enter into that of animals. This shows that that the sake of

  which they are is soul. We must here recall the two senses of 'that

  for the sake of which', viz. (a) the end to achieve which, and (b) the

  being in whose interest, anything is or is done.

  We must maintain, further, that the soul is also the cause of the

  living body as the original source of local movement. The power of

  locomotion is not found, however, in all living things. But change

  of quality and change of quantity are also due to the soul.

  Sensation is held to be a qualitative alteration, and nothing except

  what has soul in it is capable of sensation. The same holds of the

  quantitative changes which constitute growth and decay; nothing

  grows or decays naturally except what feeds itself, and nothing

  feeds itself except what has a share of soul in it.

  Empedocles is wrong in adding that growth in plants is to be

  explained, the downward rooting by the natural tendency of earth to

  travel downwards, and the upward branching by the similar natural

  tendency of fire to travel upwards. For he misinterprets up and

  down; up and down are not for all things what they are for the whole

  Cosmos: if we are to distinguish and identify organs according to

  their functions, the roots of plants are analogous to the head in

  animals. Further, we must ask what is the force that holds together

  the earth and the fire which tend to travel in contrary directions; if

  there is no counteracting force, they will be torn asunder; if there

  is, this must be the soul and the cause of nutrition and growth. By

  some the element of fire is held to be the cause of nutrition and

  growth, for it alone of the primary bodies or elements is observed

  to feed and increase itself. Hence the suggestion that in both

  plants and animals it is it which is the operative force. A concurrent

  cause in a sense it certainly is, but not the principal cause, that is

  rather the soul; for while the growth of fire goes on without limit so

  long as there is a supply of fuel, in the case of all complex wholes

  formed in the course of nature there is a limit or ratio which

  determines their size and increase, and limit and ratio are marks of

  soul but not of fire, and belong to the side of formulable essence

  rather than that of matter.

  Nutrition and reproduction are due to one and the same psychic

  power. It is necessary first to give precision to our account of food,

  for it is by this function of absorbing food that this psychic power

  is distinguished from all the others. The current view is that what

  serves as food to a living thing is what is contrary to it-not that in

  every pair of contraries each is food to the other: to be food a

  contrary must not only be transformable into the other and vice versa,

  it must also in so doing increase the bulk of the other. Many a

  contrary is transformed into its other and vice versa, where neither

  is even a quantum and so cannot increase in bulk, e.g. an invalid into

  a healthy subject. It is clear that not even those contraries which

  satisfy both the conditions mentioned above are food to one another in

  precisely the same sense; water may be said to feed fire, but not fire

  water. Where the members of the pair are elementary bodies only one of

  the contraries, it would appear, can be said to feed the other. But

  there is a difficulty here. One set of thinkers assert that like

  fed, as well as increased in amount, by like. Another set, as we

  have said, maintain the very reverse, viz. that what feeds and what is

  fed are contrary to one another; like, they argue, is incapable of

  being affected by like; but food is changed in the process of

  digestion, and change is always to what is opposite or to what is

&
nbsp; intermediate. Further, food is acted upon by what is nourished by

  it, not the other way round, as timber is worked by a carpenter and

  not conversely; there is a change in the carpenter but it is merely

  a change from not-working to working. In answering this problem it

  makes all the difference whether we mean by 'the food' the

  'finished' or the 'raw' product. If we use the word food of both, viz.

  of the completely undigested and the completely digested matter, we

  can justify both the rival accounts of it; taking food in the sense of

  undigested matter, it is the contrary of what is fed by it, taking

  it as digested it is like what is fed by it. Consequently it is

  clear that in a certain sense we may say that both parties are

  right, both wrong.

  Since nothing except what is alive can be fed, what is fed is the

  besouled body and just because it has soul in it. Hence food is

  essentially related to what has soul in it. Food has a power which

  is other than the power to increase the bulk of what is fed by it;

  so far forth as what has soul in it is a quantum, food may increase

  its quantity, but it is only so far as what has soul in it is a

  'this-somewhat' or substance that food acts as food; in that case it

  maintains the being of what is fed, and that continues to be what it

  is so long as the process of nutrition continues. Further, it is the

  agent in generation, i.e. not the generation of the individual fed but

  the reproduction of another like it; the substance of the individual

  fed is already in existence; the existence of no substance is a

  self-generation but only a self-maintenance.

  Hence the psychic power which we are now studying may be described

  as that which tends to maintain whatever has this power in it of

  continuing such as it was, and food helps it to do its work. That is

  why, if deprived of food, it must cease to be.

  The process of nutrition involves three factors, (a) what is fed,

  (b) that wherewith it is fed, (c) what does the feeding; of these

  (c) is the first soul, (a) the body which has that soul in it, (b) the

  food. But since it is right to call things after the ends they

  realize, and the end of this soul is to generate another being like

  that in which it is, the first soul ought to be named the reproductive

  soul. The expression (b) 'wherewith it is fed' is ambiguous just as is

  the expression 'wherewith the ship is steered'; that may mean either

  (i) the hand or (ii) the rudder, i.e. either (i) what is moved and

  sets in movement, or (ii) what is merely moved. We can apply this

  analogy here if we recall that all food must be capable of being

  digested, and that what produces digestion is warmth; that is why

  everything that has soul in it possesses warmth.

  We have now given an outline account of the nature of food;

  further details must be given in the appropriate place.

  5

  Having made these distinctions let us now speak of sensation in

  the widest sense. Sensation depends, as we have said, on a process

  of movement or affection from without, for it is held to be some

  sort of change of quality. Now some thinkers assert that like is

  affected only by like; in what sense this is possible and in what

  sense impossible, we have explained in our general discussion of

  acting and being acted upon.

  Here arises a problem: why do we not perceive the senses

  themselves as well as the external objects of sense, or why without

  the stimulation of external objects do they not produce sensation,

  seeing that they contain in themselves fire, earth, and all the

  other elements, which are the direct or indirect objects is so of

  sense? It is clear that what is sensitive is only potentially, not

  actually. The power of sense is parallel to what is combustible, for

  that never ignites itself spontaneously, but requires an agent which

  has the power of starting ignition; otherwise it could have set itself

  on fire, and would not have needed actual fire to set it ablaze.

  In reply we must recall that we use the word 'perceive' in two ways,

  for we say (a) that what has the power to hear or see, 'sees' or

  'hears', even though it is at the moment asleep, and also (b) that

  what is actually seeing or hearing, 'sees' or 'hears'. Hence 'sense'

  too must have two meanings, sense potential, and sense actual.

  Similarly 'to be a sentient' means either (a) to have a certain

  power or (b) to manifest a certain activity. To begin with, for a

  time, let us speak as if there were no difference between (i) being

  moved or affected, and (ii) being active, for movement is a kind of

  activity-an imperfect kind, as has elsewhere been explained.

  Everything that is acted upon or moved is acted upon by an agent which

  is actually at work. Hence it is that in one sense, as has already

  been stated, what acts and what is acted upon are like, in another

  unlike, i.e. prior to and during the change the two factors are

  unlike, after it like.

  But we must now distinguish not only between what is potential and

  what is actual but also different senses in which things can be said

  to be potential or actual; up to now we have been speaking as if

  each of these phrases had only one sense. We can speak of something as

  'a knower' either (a) as when we say that man is a knower, meaning

  that man falls within the class of beings that know or have knowledge,

  or (b) as when we are speaking of a man who possesses a knowledge of

  grammar; each of these is so called as having in him a certain

  potentiality, but there is a difference between their respective

  potentialities, the one (a) being a potential knower, because his kind

  or matter is such and such, the other (b), because he can in the

  absence of any external counteracting cause realize his knowledge in

  actual knowing at will. This implies a third meaning of 'a knower'

  (c), one who is already realizing his knowledge-he is a knower in

  actuality and in the most proper sense is knowing, e.g. this A. Both

  the former are potential knowers, who realize their respective

  potentialities, the one (a) by change of quality, i.e. repeated

  transitions from one state to its opposite under instruction, the

  other (b) by the transition from the inactive possession of sense or

  grammar to their active exercise. The two kinds of transition are

  distinct.

  Also the expression 'to be acted upon' has more than one meaning; it

  may mean either (a) the extinction of one of two contraries by the

  other, or (b) the maintenance of what is potential by the agency of

  what is actual and already like what is acted upon, with such likeness

  as is compatible with one's being actual and the other potential.

  For what possesses knowledge becomes an actual knower by a

  transition which is either not an alteration of it at all (being in

  reality a development into its true self or actuality) or at least

  an alteration in a quite different sense from the usual meaning.

  Hence it is wrong to speak of a wise man as being 'altered' when

  he uses his wisdom, just as it would be absurd to speak of a b
uilder

  as being altered when he is using his skill in building a house.

  What in the case of knowing or understanding leads from potentiality

  to actuality ought not to be called teaching but something else.

  That which starting with the power to know learns or acquires

  knowledge through the agency of one who actually knows and has the

  power of teaching either (a) ought not to be said 'to be acted upon'

  at all or (b) we must recognize two senses of alteration, viz. (i) the

  substitution of one quality for another, the first being the

  contrary of the second, or (ii) the development of an existent quality

  from potentiality in the direction of fixity or nature.

  In the case of what is to possess sense, the first transition is due

  to the action of the male parent and takes place before birth so

  that at birth the living thing is, in respect of sensation, at the

  stage which corresponds to the possession of knowledge. Actual

  sensation corresponds to the stage of the exercise of knowledge. But

  between the two cases compared there is a difference; the objects that

  excite the sensory powers to activity, the seen, the heard, c., are

  outside. The ground of this difference is that what actual sensation

  apprehends is individuals, while what knowledge apprehends is

  universals, and these are in a sense within the soul. That is why a

  man can exercise his knowledge when he wishes, but his sensation

  does not depend upon himself a sensible object must be there. A

  similar statement must be made about our knowledge of what is

  sensible-on the same ground, viz. that the sensible objects are

  individual and external.

  A later more appropriate occasion may be found thoroughly to clear

  up all this. At present it must be enough to recognize the

  distinctions already drawn; a thing may be said to be potential in

  either of two senses, (a) in the sense in which we might say of a

  boy that he may become a general or (b) in the sense in which we might

  say the same of an adult, and there are two corresponding senses of