350 BC

                                  ON THE SOUL

                                  by Aristotle

                           translated by J. A. Smith

                              Book I ---- Part I/II

                                 1

  HOLDING as we do that, while knowledge of any kind is a thing to
be honoured and prized, one kind of it may, either by reason of its
greater exactness or of a higher dignity and greater wonderfulness
in its objects, be more honourable and precious than another, on
both accounts we should naturally be led to place in the front rank
the study of the soul. The knowledge of the soul admittedly
contributes greatly to the advance of truth in general, and, above
all, to our understanding of Nature, for the soul is in some sense the
principle of animal life. Our aim is to grasp and understand, first
its essential nature, and secondly its properties; of these some are
taught to be affections proper to the soul itself, while others are
considered to attach to the animal owing to the presence within it
of soul.

  To attain any assured knowledge about the soul is one of the most
difficult things in the world. As the form of question which here
presents itself, viz. the question 'What is it?', recurs in other
fields, it might be supposed that there was some single method of
inquiry applicable to all objects whose essential nature (as we are
endeavouring to ascertain there is for derived properties the single
method of demonstration); in that case what we should have to seek for
would be this unique method. But if there is no such single and
general method for solving the question of essence, our task becomes
still more difficult; in the case of each different subject we shall
have to determine the appropriate process of investigation. If to this
there be a clear answer, e.g. that the process is demonstration or
division, or some known method, difficulties and hesitations still
beset us-with what facts shall we begin the inquiry? For the facts
which form the starting-points in different subjects must be
different, as e.g. in the case of numbers and surfaces.

  First, no doubt, it is necessary to determine in which of the
summa genera soul lies, what it is; is it 'a this-somewhat, 'a
substance, or is it a quale or a quantum, or some other of the
remaining kinds of predicates which we have distinguished? Further,
does soul belong to the class of potential existents, or is it not
rather an actuality? Our answer to this question is of the greatest
importance.

  We must consider also whether soul is divisible or is without parts,
and whether it is everywhere homogeneous or not; and if not
homogeneous, whether its various forms are different specifically or
generically: up to the present time those who have discussed and
investigated soul seem to have confined themselves to the human
soul. We must be careful not to ignore the question whether soul can
be defined in a single unambiguous formula, as is the case with
animal, or whether we must not give a separate formula for each of it,
as we do for horse, dog, man, god (in the latter case the
'universal' animal-and so too every other 'common predicate'-being
treated either as nothing at all or as a later product). Further, if
what exists is not a plurality of souls, but a plurality of parts of
one soul, which ought we to investigate first, the whole soul or its
parts? (It is also a difficult problem to decide which of these
parts are in nature distinct from one another.) Again, which ought
we to investigate first, these parts or their functions, mind or
thinking, the faculty or the act of sensation, and so on? If the
investigation of the functions precedes that of the parts, the further
question suggests itself: ought we not before either to consider the
correlative objects, e.g. of sense or thought? It seems not only
useful for the discovery of the causes of the derived properties of
substances to be acquainted with the essential nature of those
substances (as in mathematics it is useful for the understanding of
the property of the equality of the interior angles of a triangle to
two right angles to know the essential nature of the straight and
the curved or of the line and the plane) but also conversely, for
the knowledge of the essential nature of a substance is largely
promoted by an acquaintance with its properties: for, when we are able
to give an account conformable to experience of all or most of the
properties of a substance, we shall be in the most favourable position
to say something worth saying about the essential nature of that
subject; in all demonstration a definition of the essence is
required as a starting-point, so that definitions which do not
enable us to discover the derived properties, or which fail to
facilitate even a conjecture about them, must obviously, one and
all, be dialectical and futile.

  A further problem presented by the affections of soul is this: are
they all affections of the complex of body and soul, or is there any
one among them peculiar to the soul by itself? To determine this is
indispensable but difficult. If we consider the majority of them,
there seems to be no case in which the soul can act or be acted upon
without involving the body; e.g. anger, courage, appetite, and
sensation generally. Thinking seems the most probable exception; but
if this too proves to be a form of imagination or to be impossible
without imagination, it too requires a body as a condition of its
existence. If there is any way of acting or being acted upon proper to
soul, soul will be capable of separate existence; if there is none,
its separate existence is impossible. In the latter case, it will be
like what is straight, which has many properties arising from the
straightness in it, e.g. that of touching a bronze sphere at a
point, though straightness divorced from the other constituents of the
straight thing cannot touch it in this way; it cannot be so divorced
at all, since it is always found in a body. It therefore seems that
all the affections of soul involve a body-passion, gentleness, fear,
pity, courage, joy, loving, and hating; in all these there is a
concurrent affection of the body. In support of this we may point to
the fact that, while sometimes on the occasion of violent and striking
occurrences there is no excitement or fear felt, on others faint and
feeble stimulations produce these emotions, viz. when the body is
already in a state of tension resembling its condition when we are
angry. Here is a still clearer case: in the absence of any external
cause of terror we find ourselves experiencing the feelings of a man
in terror. From all this it is obvious that the affections of soul are
enmattered formulable essences.

  Consequently their definitions ought to correspond, e.g. anger
should be defined as a certain mode of movement of such and such a
body (or part or faculty of a body) by this or that cause and for this
or that end. That is precisely why the study of the soul must fall
within the science of Nature, at least so far as in its affections
it manifests this double character. Hence a physicist would define
an affection of soul differently from a dialectician; the latter would
define e.g. anger as the appetite for returning pain for pain, or
something like that, while the former would define it as a boiling
of the blood or warm substance surround the heart. The latter
assigns the material conditions, the former the form or formulable
essence; for what he states is the formulable essence of the fact,
though for its actual existence there must be embodiment of it in a
material such as is described by the other. Thus the essence of a
house is assigned in such a formula as 'a shelter against
destruction by wind, rain, and heat'; the physicist would describe
it as 'stones, bricks, and timbers'; but there is a third possible
description which would say that it was that form in that material
with that purpose or end. Which, then, among these is entitled to be
regarded as the genuine physicist? The one who confines himself to the
material, or the one who restricts himself to the formulable essence
alone? Is it not rather the one who combines both in a single formula?
If this is so, how are we to characterize the other two? Must we not
say that there is no type of thinker who concerns himself with those
qualities or attributes of the material which are in fact
inseparable from the material, and without attempting even in
thought to separate them? The physicist is he who concerns himself
with all the properties active and passive of bodies or materials thus
or thus defined; attributes not considered as being of this
character he leaves to others, in certain cases it may be to a
specialist, e.g. a carpenter or a physician, in others (a) where
they are inseparable in fact, but are separable from any particular
kind of body by an effort of abstraction, to the mathematician, (b)
where they are separate both in fact and in thought from body
altogether, to the First Philosopher or metaphysician. But we must
return from this digression, and repeat that the affections of soul
are inseparable from the material substratum of animal life, to
which we have seen that such affections, e.g. passion and fear,
attach, and have not the same mode of being as a line or a plane.

                                 2

  For our study of soul it is necessary, while formulating the
problems of which in our further advance we are to find the solutions,
to call into council the views of those of our predecessors who have
declared any opinion on this subject, in order that we may profit by
whatever is sound in their suggestions and avoid their errors.

  The starting-point of our inquiry is an exposition of those
characteristics which have chiefly been held to belong to soul in
its very nature. Two characteristic marks have above all others been
recognized as distinguishing that which has soul in it from that which
has not-movement and sensation. It may be said that these two are what
our predecessors have fixed upon as characteristic of soul.

  Some say that what originates movement is both pre-eminently and
primarily soul; believing that what is not itself moved cannot
originate movement in another, they arrived at the view that soul
belongs to the class of things in movement. This is what led
Democritus to say that soul is a sort of fire or hot substance; his
'forms' or atoms are infinite in number; those which are spherical
he calls fire and soul, and compares them to the motes in the air
which we see in shafts of light coming through windows; the mixture of
seeds of all sorts he calls the elements of the whole of Nature
(Leucippus gives a similar account); the spherical atoms are
identified with soul because atoms of that shape are most adapted to
permeate everywhere, and to set all the others moving by being
themselves in movement. This implies the view that soul is identical
with what produces movement in animals. That is why, further, they
regard respiration as the characteristic mark of life; as the
environment compresses the bodies of animals, and tends to extrude
those atoms which impart movement to them, because they themselves are
never at rest, there must be a reinforcement of these by similar atoms
coming in from without in the act of respiration; for they prevent the
extrusion of those which are already within by counteracting the
compressing and consolidating force of the environment; and animals
continue to live only so long as they are able to maintain this
resistance.

  The doctrine of the Pythagoreans seems to rest upon the same
ideas; some of them declared the motes in air, others what moved them,
to be soul. These motes were referred to because they are seen
always in movement, even in a complete calm.

  The same tendency is shown by those who define soul as that which
moves itself; all seem to hold the view that movement is what is
closest to the nature of soul, and that while all else is moved by
soul, it alone moves itself. This belief arises from their never
seeing anything originating movement which is not first itself moved.

  Similarly also Anaxagoras (and whoever agrees with him in saying
that mind set the whole in movement) declares the moving cause of
things to be soul. His position must, however, be distinguished from
that of Democritus. Democritus roundly identifies soul and mind, for
he identifies what appears with what is true-that is why he commends
Homer for the phrase 'Hector lay with thought distraught'; he does not
employ mind as a special faculty dealing with truth, but identifies
soul and mind. What Anaxagoras says about them is more obscure; in
many places he tells us that the cause of beauty and order is mind,
elsewhere that it is soul; it is found, he says, in all animals, great
and small, high and low, but mind (in the sense of intelligence)
appears not to belong alike to all animals, and indeed not even to all
human beings.

  All those, then, who had special regard to the fact that what has
soul in it is moved, adopted the view that soul is to be identified
with what is eminently originative of movement. All, on the other
hand, who looked to the fact that what has soul in it knows or
perceives what is, identify soul with the principle or principles of
Nature, according as they admit several such principles or one only.
Thus Empedocles declares that it is formed out of all his elements,
each of them also being soul; his words are:

  For 'tis by Earth we see Earth, by Water Water,

  By Ether Ether divine, by Fire destructive Fire,

  By Love Love, and Hate by cruel Hate.

  In the same way Plato in the Timaeus fashions soul out of his
elements; for like, he holds, is known by like, and things are
formed out of the principles or elements, so that soul must be so too.
Similarly also in his lectures 'On Philosophy' it was set forth that
the Animal-itself is compounded of the Idea itself of the One together
with the primary length, breadth, and depth, everything else, the
objects of its perception, being similarly constituted. Again he
puts his view in yet other terms: Mind is the monad, science or
knowledge the dyad (because it goes undeviatingly from one point to
another), opinion the number of the plane, sensation the number of the
solid; the numbers are by him expressly identified with the Forms
themselves or principles, and are formed out of the elements; now
things are apprehended either by mind or science or opinion or
sensation, and these same numbers are the Forms of things.

  Some thinkers, accepting both premisses, viz. that the soul is
both originative of movement and cognitive, have compounded it of both
and declared the soul to be a self-moving number.

  As to the nature and number of the first principles opinions differ.
The difference is greatest between those who regard them as
corporeal and those who regard them as incorporeal, and from both
dissent those who make a blend and draw their principles from both
sources. The number of principles is also in dispute; some admit one
only, others assert several. There is a consequent diversity in
their several accounts of soul; they assume, naturally enough, that
what is in its own nature originative of movement must be among what
is primordial. That has led some to regard it as fire, for fire is the
subtlest of the elements and nearest to incorporeality; further, in
the most primary sense, fire both is moved and originates movement
in all the others.

  Democritus has expressed himself more ingeniously than the rest on
the grounds for ascribing each of these two characters to soul; soul
and mind are, he says, one and the same thing, and this thing must
be one of the primary and indivisible bodies, and its power of
originating movement must be due to its fineness of grain and the
shape of its atoms; he says that of all the shapes the spherical is
the most mobile, and that this is the shape of the particles of fire
and mind.

  Anaxagoras, as we said above, seems to distinguish between soul
and mind, but in practice he treats them as a single substance, except
that it is mind that he specially posits as the principle of all
things; at any rate what he says is that mind alone of all that is
simple, unmixed, and pure. He assigns both characteristics, knowing
and origination of movement, to the same principle, when he says
that it was mind that set the whole in movement.

  Thales, too, to judge from what is recorded about him, seems to have
held soul to be a motive force, since he said that the magnet has a
soul in it because it moves the iron.

  Diogenes (and others) held the soul to be air because he believed
air to be finest in grain and a first principle; therein lay the
grounds of the soul's powers of knowing and originating movement. As
the primordial principle from which all other things are derived, it
is cognitive; as finest in grain, it has the power to originate
movement.

  Heraclitus too says that the first principle-the 'warm exhalation'
of which, according to him, everything else is composed-is soul;
further, that this exhalation is most incorporeal and in ceaseless
flux; that what is in movement requires that what knows it should be
in movement; and that all that is has its being essentially in
movement (herein agreeing with the majority).

  Alcmaeon also seems to have held a similar view about soul; he
says that it is immortal because it resembles 'the immortals,' and
that this immortality belongs to it in virtue of its ceaseless
movement; for all the 'things divine,' moon, sun, the planets, and the
whole heavens, are in perpetual movement.

  of More superficial writers, some, e.g. Hippo, have pronounced it to
be water; they seem to have argued from the fact that the seed of
all animals is fluid, for Hippo tries to refute those who say that the
soul is blood, on the ground that the seed, which is the primordial
soul, is not blood.

  Another group (Critias, for example) did hold it to be blood; they
take perception to be the most characteristic attribute of soul, and
hold that perceptiveness is due to the nature of blood.

  Each of the elements has thus found its partisan, except earth-earth
has found no supporter unless we count as such those who have declared
soul to be, or to be compounded of, all the elements. All, then, it
may be said, characterize the soul by three marks, Movement,
Sensation, Incorporeality, and each of these is traced back to the
first principles. That is why (with one exception) all those who
define the soul by its power of knowing make it either an element or
constructed out of the elements. The language they all use is similar;
like, they say, is known by like; as the soul knows everything, they
construct it out of all the principles. Hence all those who admit
but one cause or element, make the soul also one (e.g. fire or air),
while those who admit a multiplicity of principles make the soul
also multiple. The exception is Anaxagoras; he alone says that mind is
impassible and has nothing in common with anything else. But, if
this is so, how or in virtue of what cause can it know? That
Anaxagoras has not explained, nor can any answer be inferred from
his words. All who acknowledge pairs of opposites among their
principles, construct the soul also out of these contraries, while
those who admit as principles only one contrary of each pair, e.g.
either hot or cold, likewise make the soul some one of these. That
is why, also, they allow themselves to be guided by the names; those
who identify soul with the hot argue that sen (to live) is derived
from sein (to boil), while those who identify it with the cold say
that soul (psuche) is so called from the process of respiration and
(katapsuxis). Such are the traditional opinions concerning soul,
together with the grounds on which they are maintained.

                                 3

  We must begin our examination with movement; for doubtless, not only
is it false that the essence of soul is correctly described by those
who say that it is what moves (or is capable of moving) itself, but it
is an impossibility that movement should be even an attribute of it.

  We have already pointed out that there is no necessity that what
originates movement should itself be moved. There are two senses in
which anything may be moved-either (a) indirectly, owing to
something other than itself, or (b) directly, owing to itself.
Things are 'indirectly moved' which are moved as being contained in
something which is moved, e.g. sailors in a ship, for they are moved
in a different sense from that in which the ship is moved; the ship is
'directly moved', they are 'indirectly moved', because they are in a
moving vessel. This is clear if we consider their limbs; the
movement proper to the legs (and so to man) is walking, and in this
case the sailors tare not walking. Recognizing the double sense of
'being moved', what we have to consider now is whether the soul is
'directly moved' and participates in such direct movement.

  There are four species of movement-locomotion, alteration,
diminution, growth; consequently if the soul is moved, it must be
moved with one or several or all of these species of movement. Now
if its movement is not incidental, there must be a movement natural to
it, and, if so, as all the species enumerated involve place, place
must be natural to it. But if the essence of soul be to move itself,
its being moved cannot be incidental to-as it is to what is white or
three cubits long; they too can be moved, but only incidentally-what
is moved is that of which 'white' and 'three cubits long' are the
attributes, the body in which they inhere; hence they have no place:
but if the soul naturally partakes in movement, it follows that it
must have a place.

  Further, if there be a movement natural to the soul, there must be a
counter-movement unnatural to it, and conversely. The same applies
to rest as well as to movement; for the terminus ad quem of a
thing's natural movement is the place of its natural rest, and
similarly the terminus ad quem of its enforced movement is the place
of its enforced rest. But what meaning can be attached to enforced
movements or rests of the soul, it is difficult even to imagine.

  Further, if the natural movement of the soul be upward, the soul
must be fire; if downward, it must be earth; for upward and downward
movements are the definitory characteristics of these bodies. The same
reasoning applies to the intermediate movements, termini, and
bodies. Further, since the soul is observed to originate movement in
the body, it is reasonable to suppose that it transmits to the body
the movements by which it itself is moved, and so, reversing the
order, we may infer from the movements of the body back to similar
movements of the soul. Now the body is moved from place to place
with movements of locomotion. Hence it would follow that the soul
too must in accordance with the body change either its place as a
whole or the relative places of its parts. This carries with it the
possibility that the soul might even quit its body and re-enter it,
and with this would be involved the possibility of a resurrection of
animals from the dead. But, it may be contended, the soul can be moved
indirectly by something else; for an animal can be pushed out of its
course. Yes, but that to whose essence belongs the power of being
moved by itself, cannot be moved by something else except
incidentally, just as what is good by or in itself cannot owe its
goodness to something external to it or to some end to which it is a
means.

  If the soul is moved, the most probable view is that what moves it
is sensible things.

  We must note also that, if the soul moves itself, it must be the
mover itself that is moved, so that it follows that if movement is
in every case a displacement of that which is in movement, in that
respect in which it is said to be moved, the movement of the soul must
be a departure from its essential nature, at least if its
self-movement is essential to it, not incidental.

  Some go so far as to hold that the movements which the soul
imparts to the body in which it is are the same in kind as those
with which it itself is moved. An example of this is Democritus, who
uses language like that of the comic dramatist Philippus, who accounts
for the movements that Daedalus imparted to his wooden Aphrodite by
saying that he poured quicksilver into it; similarly Democritus says
that the spherical atoms which according to him constitute soul, owing
to their own ceaseless movements draw the whole body after them and so
produce its movements. We must urge the question whether it is these
very same atoms which produce rest also-how they could do so, it is
difficult and even impossible to say. And, in general, we may object
that it is not in this way that the soul appears to originate movement
in animals-it is through intention or process of thinking.

  It is in the same fashion that the Timaeus also tries to give a
physical account of how the soul moves its body; the soul, it is there
said, is in movement, and so owing to their mutual implication moves
the body also. After compounding the soul-substance out of the
elements and dividing it in accordance with the harmonic numbers, in
order that it may possess a connate sensibility for 'harmony' and that
the whole may move in movements well attuned, the Demiurge bent the
straight line into a circle; this single circle he divided into two
circles united at two common points; one of these he subdivided into
seven circles. All this implies that the movements of the soul are
identified with the local movements of the heavens.

    Now, in the first place, it is a mistake to say that the soul is a
spatial magnitude. It is evident that Plato means the soul of the
whole to be like the sort of soul which is called mind not like the
sensitive or the desiderative soul, for the movements of neither of
these are circular. Now mind is one and continuous in the sense in
which the process of thinking is so, and thinking is identical with
the thoughts which are its parts; these have a serial unity like
that of number, not a unity like that of a spatial magnitude. Hence
mind cannot have that kind of unity either; mind is either without
parts or is continuous in some other way than that which characterizes
a spatial magnitude. How, indeed, if it were a spatial magnitude,
could mind possibly think? Will it think with any one indifferently of
its parts? In this case, the 'part' must be understood either in the
sense of a spatial magnitude or in the sense of a point (if a point
can be called a part of a spatial magnitude). If we accept the
latter alternative, the points being infinite in number, obviously the
mind can never exhaustively traverse them; if the former, the mind
must think the same thing over and over again, indeed an infinite
number of times (whereas it is manifestly possible to think a thing
once only). If contact of any part whatsoever of itself with the
object is all that is required, why need mind move in a circle, or
indeed possess magnitude at all? On the other hand, if contact with
the whole circle is necessary, what meaning can be given to the
contact of the parts? Further, how could what has no parts think
what has parts, or what has parts think what has none? We must
identify the circle referred to with mind; for it is mind whose
movement is thinking, and it is the circle whose movement is
revolution, so that if thinking is a movement of revolution, the
circle which has this characteristic movement must be mind.

  If the circular movement is eternal, there must be something which
mind is always thinking-what can this be? For all practical
processes of thinking have limits-they all go on for the sake of
something outside the process, and all theoretical processes come to a
close in the same way as the phrases in speech which express processes
and results of thinking. Every such linguistic phrase is either
definitory or demonstrative. Demonstration has both a starting-point
and may be said to end in a conclusion or inferred result; even if the
process never reaches final completion, at any rate it never returns
upon itself again to its starting-point, it goes on assuming a fresh
middle term or a fresh extreme, and moves straight forward, but
circular movement returns to its starting-point. Definitions, too, are
closed groups of terms.

  Further, if the same revolution is repeated, mind must repeatedly
think the same object.

  Further, thinking has more resemblance to a coming to rest or arrest
than to a movement; the same may be said of inferring.

  It might also be urged that what is difficult and enforced is
incompatible with blessedness; if the movement of the soul is not of
its essence, movement of the soul must be contrary to its nature. It
must also be painful for the soul to be inextricably bound up with the
body; nay more, if, as is frequently said and widely accepted, it is
better for mind not to be embodied, the union must be for it
undesirable.

  Further, the cause of the revolution of the heavens is left obscure.
It is not the essence of soul which is the cause of this circular
movement-that movement is only incidental to soul-nor is, a
fortiori, the body its cause. Again, it is not even asserted that it
is better that soul should be so moved; and yet the reason for which
God caused the soul to move in a circle can only have been that
movement was better for it than rest, and movement of this kind better
than any other. But since this sort of consideration is more
appropriate to another field of speculation, let us dismiss it for the
present.

  The view we have just been examining, in company with most
theories about the soul, involves the following absurdity: they all
join the soul to a body, or place it in a body, without adding any
specification of the reason of their union, or of the bodily
conditions required for it. Yet such explanation can scarcely be
omitted; for some community of nature is presupposed by the fact
that the one acts and the other is acted upon, the one moves and the
other is moved; interaction always implies a special nature in the two
interagents. All, however, that these thinkers do is to describe the
specific characteristics of the soul; they do not try to determine
anything about the body which is to contain it, as if it were
possible, as in the Pythagorean myths, that any soul could be
clothed upon with any body-an absurd view, for each body seems to have
a form and shape of its own. It is as absurd as to say that the art of
carpentry could embody itself in flutes; each art must use its
tools, each soul its body.

                                 4

  There is yet another theory about soul, which has commended itself
to many as no less probable than any of those we have hitherto
mentioned, and has rendered public account of itself in the court of
popular discussion. Its supporters say that the soul is a kind of
harmony, for (a) harmony is a blend or composition of contraries,
and (b) the body is compounded out of contraries. Harmony, however, is
a certain proportion or composition of the constituents blended, and
soul can be neither the one nor the other of these. Further, the power
of originating movement cannot belong to a harmony, while almost all
concur in regarding this as a principal attribute of soul. It is
more appropriate to call health (or generally one of the good states
of the body) a harmony than to predicate it of the soul. The absurdity
becomes most apparent when we try to attribute the active and
passive affections of the soul to a harmony; the necessary
readjustment of their conceptions is difficult. Further, in using
the word 'harmony' we have one or other of two cases in our mind;
the most proper sense is in relation to spatial magnitudes which
have motion and position, where harmony means the disposition and
cohesion of their parts in such a manner as to prevent the
introduction into the whole of anything homogeneous with it, and the
secondary sense, derived from the former, is that in which it means
the ratio between the constituents so blended; in neither of these
senses is it plausible to predicate it of soul. That soul is a harmony
in the sense of the mode of composition of the parts of the body is
a view easily refutable; for there are many composite parts and
those variously compounded; of what bodily part is mind or the
sensitive or the appetitive faculty the mode of composition? And
what is the mode of composition which constitutes each of them? It
is equally absurd to identify the soul with the ratio of the
mixture; for the mixture which makes flesh has a different ratio
between the elements from that which makes bone. The consequence of
this view will therefore be that distributed throughout the whole body
there will be many souls, since every one of the bodily parts is a
different mixture of the elements, and the ratio of mixture is in each
case a harmony, i.e. a soul.

  From Empedocles at any rate we might demand an answer to the
following question for he says that each of the parts of the body is
what it is in virtue of a ratio between the elements: is the soul
identical with this ratio, or is it not rather something over and
above this which is formed in the parts? Is love the cause of any
and every mixture, or only of those that are in the right ratio? Is
love this ratio itself, or is love something over and above this? Such
are the problems raised by this account. But, on the other hand, if
the soul is different from the mixture, why does it disappear at one
and the same moment with that relation between the elements which
constitutes flesh or the other parts of the animal body? Further, if
the soul is not identical with the ratio of mixture, and it is
consequently not the case that each of the parts has a soul, what is
that which perishes when the soul quits the body?

  That the soul cannot either be a harmony, or be moved in a circle,
is clear from what we have said. Yet that it can be moved incidentally
is, as we said above, possible, and even that in a sense it can move
itself, i.e. in the sense that the vehicle in which it is can be
moved, and moved by it; in no other sense can the soul be moved in
space.

  More legitimate doubts might remain as to its movement in view of
the following facts. We speak of the soul as being pained or
pleased, being bold or fearful, being angry, perceiving, thinking. All
these are regarded as modes of movement, and hence it might be
inferred that the soul is moved. This, however, does not necessarily
follow. We may admit to the full that being pained or pleased, or
thinking, are movements (each of them a 'being moved'), and that the
movement is originated by the soul. For example we may regard anger or
fear as such and such movements of the heart, and thinking as such and
such another movement of that organ, or of some other; these
modifications may arise either from changes of place in certain
parts or from qualitative alterations (the special nature of the parts
and the special modes of their changes being for our present purpose
irrelevant). Yet to say that it is the soul which is angry is as
inexact as it would be to say that it is the soul that weaves webs
or builds houses. It is doubtless better to avoid saying that the soul
pities or learns or thinks and rather to say that it is the man who
does this with his soul. What we mean is not that the movement is in
the soul, but that sometimes it terminates in the soul and sometimes
starts from it, sensation e.g. coming from without inwards, and
reminiscence starting from the soul and terminating with the
movements, actual or residual, in the sense organs.

  The case of mind is different; it seems to be an independent
substance implanted within the soul and to be incapable of being
destroyed. If it could be destroyed at all, it would be under the
blunting influence of old age. What really happens in respect of
mind in old age is, however, exactly parallel to what happens in the
case of the sense organs; if the old man could recover the proper kind
of eye, he would see just as well as the young man. The incapacity
of old age is due to an affection not of the soul but of its
vehicle, as occurs in drunkenness or disease. Thus it is that in old
age the activity of mind or intellectual apprehension declines only
through the decay of some other inward part; mind itself is
impassible. Thinking, loving, and hating are affections not of mind,
but of that which has mind, so far as it has it. That is why, when
this vehicle decays, memory and love cease; they were activities not
of mind, but of the composite which has perished; mind is, no doubt,
something more divine and impassible. That the soul cannot be moved is
therefore clear from what we have said, and if it cannot be moved at
all, manifestly it cannot be moved by itself.

  Of all the opinions we have enumerated, by far the most unreasonable
is that which declares the soul to be a self-moving number; it
involves in the first place all the impossibilities which follow
from regarding the soul as moved, and in the second special
absurdities which follow from calling it a number. How we to imagine a
unit being moved? By what agency? What sort of movement can be
attributed to what is without parts or internal differences? If the
unit is both originative of movement and itself capable of being
moved, it must contain difference.

  Further, since they say a moving line generates a surface and a
moving point a line, the movements of the psychic units must be
lines (for a point is a unit having position, and the number of the
soul is, of course, somewhere and has position).

  Again, if from a number a number or a unit is subtracted, the
remainder is another number; but plants and many animals when
divided continue to live, and each segment is thought to retain the
same kind of soul.

  It must be all the same whether we speak of units or corpuscles; for
if the spherical atoms of Democritus became points, nothing being
retained but their being a quantum, there must remain in each a moving
and a moved part, just as there is in what is continuous; what happens
has nothing to do with the size of the atoms, it depends solely upon
their being a quantum. That is why there must be something to
originate movement in the units. If in the animal what originates
movement is the soul, so also must it be in the case of the number, so
that not the mover and the moved together, but the mover only, will be
the soul. But how is it possible for one of the units to fulfil this
function of originating movement? There must be some difference
between such a unit and all the other units, and what difference can
there be between one placed unit and another except a difference of
position? If then, on the other hand, these psychic units within the
body are different from the points of the body, there will be two sets
of units both occupying the same place; for each unit will occupy a
point. And yet, if there can be two, why cannot there be an infinite
number? For if things can occupy an indivisible lace, they must
themselves be indivisible. If, on the other hand, the points of the
body are identical with the units whose number is the soul, or if
the number of the points in the body is the soul, why have not all
bodies souls? For all bodies contain points or an infinity of points.

  Further, how is it possible for these points to be isolated or
separated from their bodies, seeing that lines cannot be resolved into
points?

                                 5

  The result is, as we have said, that this view, while on the one
side identical with that of those who maintain that soul is a subtle
kind of body, is on the other entangled in the absurdity peculiar to
Democritus' way of describing the manner in which movement is
originated by soul. For if the soul is present throughout the whole
percipient body, there must, if the soul be a kind of body, be two
bodies in the same place; and for those who call it a number, there
must be many points at one point, or every body must have a soul,
unless the soul be a different sort of number-other, that is, than the
sum of the points existing in a body. Another consequence that follows
is that the animal must be moved by its number precisely in the way
that Democritus explained its being moved by his spherical psychic
atoms. What difference does it make whether we speak of small
spheres or of large units, or, quite simply, of units in movement? One
way or another, the movements of the animal must be due to their
movements. Hence those who combine movement and number in the same
subject lay themselves open to these and many other similar
absurdities. It is impossible not only that these characters should
give the definition of soul-it is impossible that they should even
be attributes of it. The point is clear if the attempt be made to
start from this as the account of soul and explain from it the
affections and actions of the soul, e.g. reasoning, sensation,
pleasure, pain, &c. For, to repeat what we have said earlier, movement
and number do not facilitate even conjecture about the derivative
properties of soul.

  Such are the three ways in which soul has traditionally been
defined; one group of thinkers declared it to be that which is most
originative of movement because it moves itself, another group to be
the subtlest and most nearly incorporeal of all kinds of body. We have
now sufficiently set forth the difficulties and inconsistencies to
which these theories are exposed. It remains now to examine the
doctrine that soul is composed of the elements.

  The reason assigned for this doctrine is that thus the soul may
perceive or come to know everything that is, but the theory
necessarily involves itself in many impossibilities. Its upholders
assume that like is known only by like, and imagine that by
declaring the soul to be composed of the elements they succeed in
identifying the soul with all the things it is capable of
apprehending. But the elements are not the only things it knows; there
are many others, or, more exactly, an infinite number of others,
formed out of the elements. Let us admit that the soul knows or
perceives the elements out of which each of these composites is made
up; but by what means will it know or perceive the composite whole,
e.g. what God, man, flesh, bone (or any other compound) is? For each
is, not merely the elements of which it is composed, but those
elements combined in a determinate mode or ratio, as Empedocles
himself says of bone,

  The kindly Earth in its broad-bosomed moulds

      Won of clear Water two parts out of eight,

      And four of Fire; and so white bones were formed.

  Nothing, therefore, will be gained by the presence of the elements
in the soul, unless there be also present there the various formulae
of proportion and the various compositions in accordance with them.
Each element will indeed know its fellow outside, but there will be no
knowledge of bone or man, unless they too are present in the
constitution of the soul. The impossibility of this needs no
pointing out; for who would suggest that stone or man could enter into
the constitution of the soul? The same applies to 'the good' and
'the not-good', and so on.

  Further, the word 'is' has many meanings: it may be used of a 'this'
or substance, or of a quantum, or of a quale, or of any other of the
kinds of predicates we have distinguished. Does the soul consist of
all of these or not? It does not appear that all have common elements.
Is the soul formed out of those elements alone which enter into
substances? so how will it be able to know each of the other kinds
of thing? Will it be said that each kind of thing has elements or
principles of its own, and that the soul is formed out of the whole of
these? In that case, the soul must be a quantum and a quale and a
substance. But all that can be made out of the elements of a quantum
is a quantum, not a substance. These (and others like them) are the
consequences of the view that the soul is composed of all the
elements.

  It is absurd, also, to say both (a) that like is not capable of
being affected by like, and (b) that like is perceived or known by
like, for perceiving, and also both thinking and knowing, are, on
their own assumption, ways of being affected or moved.

  There are many puzzles and difficulties raised by saying, as
Empedocles does, that each set of things is known by means of its
corporeal elements and by reference to something in soul which is like
them, and additional testimony is furnished by this new consideration;
for all the parts of the animal body which consist wholly of earth
such as bones, sinews, and hair seem to be wholly insensitive and
consequently not perceptive even of objects earthy like themselves, as
they ought to have been.

  Further, each of the principles will have far more ignorance than
knowledge, for though each of them will know one thing, there will
be many of which it will be ignorant. Empedocles at any rate must
conclude that his God is the least intelligent of all beings, for of
him alone is it true that there is one thing, Strife, which he does
not know, while there is nothing which mortal beings do not know,
for ere is nothing which does not enter into their composition.

  In general, we may ask, Why has not everything a soul, since
everything either is an element, or is formed out of one or several or
all of the elements? Each must certainly know one or several or all.

  The problem might also be raised, What is that which unifies the
elements into a soul? The elements correspond, it would appear, to the
matter; what unites them, whatever it is, is the supremely important
factor. But it is impossible that there should be something superior
to, and dominant over, the soul (and a fortiori over the mind); it
is reasonable to hold that mind is by nature most primordial and
dominant, while their statement that it is the elements which are
first of all that is.

  All, both those who assert that the soul, because of its knowledge
or perception of what is compounded out of the elements, and is
those who assert that it is of all things the most originative of
movement, fail to take into consideration all kinds of soul. In fact
(1) not all beings that perceive can originate movement; there
appear to be certain animals which stationary, and yet local
movement is the only one, so it seems, which the soul originates in
animals. And (2) the same object-on holds against all those who
construct mind and the perceptive faculty out of the elements; for
it appears that plants live, and yet are not endowed with locomotion
or perception, while a large number of animals are without discourse
of reason. Even if these points were waived and mind admitted to be
a part of the soul (and so too the perceptive faculty), still, even
so, there would be kinds and parts of soul of which they had failed to
give any account.

  The same objection lies against the view expressed in the 'Orphic'
poems: there it is said that the soul comes in from the whole when
breathing takes place, being borne in upon the winds. Now this
cannot take place in the case of plants, nor indeed in the case of
certain classes of animal, for not all classes of animal breathe. This
fact has escaped the notice of the holders of this view.

  If we must construct the soul out of the elements, there is no
necessity to suppose that all the elements enter into its
construction; one element in each pair of contraries will suffice to
enable it to know both that element itself and its contrary. By
means of the straight line we know both itself and the curved-the
carpenter's rule enables us to test both-but what is curved does not
enable us to distinguish either itself or the straight. Certain
thinkers say that soul is intermingled in the whole universe, and it
is perhaps for that reason that Thales came to the opinion that all
things are full of gods. This presents some difficulties: Why does the
soul when it resides in air or fire not form an animal, while it
does so when it resides in mixtures of the elements, and that although
it is held to be of higher quality when contained in the former?
(One might add the question, why the soul in air is maintained to be
higher and more immortal than that in animals.) Both possible ways
of replying to the former question lead to absurdity or paradox; for
it is beyond paradox to say that fire or air is an animal, and it is
absurd to refuse the name of animal to what has soul in it. The
opinion that the elements have soul in them seems to have arisen
from the doctrine that a whole must be homogeneous with its parts.
If it is true that animals become animate by drawing into themselves a
portion of what surrounds them, the partisans of this view are bound
to say that the soul of the Whole too is homogeneous with all its
parts. If the air sucked in is homogeneous, but soul heterogeneous,
clearly while some part of soul will exist in the inbreathed air, some
other part will not. The soul must either be homogeneous, or such that
there are some parts of the Whole in which it is not to be found.

  From what has been said it is now clear that knowing as an attribute
of soul cannot be explained by soul's being composed of the
elements, and that it is neither sound nor true to speak of soul as
moved. But since (a) knowing, perceiving, opining, and further (b)
desiring, wishing, and generally all other modes of appetition, belong
to soul, and (c) the local movements of animals, and (d) growth,
maturity, and decay are produced by the soul, we must ask whether each
of these is an attribute of the soul as a whole, i.e. whether it is
with the whole soul we think, perceive, move ourselves, act or are
acted upon, or whether each of them requires a different part of the
soul? So too with regard to life. Does it depend on one of the parts
of soul? Or is it dependent on more than one? Or on all? Or has it
some quite other cause?

  Some hold that the soul is divisible, and that one part thinks,
another desires. If, then, its nature admits of its being divided,
what can it be that holds the parts together? Surely not the body;
on the contrary it seems rather to be the soul that holds the body
together; at any rate when the soul departs the body disintegrates and
decays. If, then, there is something else which makes the soul one,
this unifying agency would have the best right to the name of soul,
and we shall have to repeat for it the question: Is it one or
multipartite? If it is one, why not at once admit that 'the soul' is
one? If it has parts, once more the question must be put: What holds
its parts together, and so ad infinitum?

  The question might also be raised about the parts of the soul:
What is the separate role of each in relation to the body? For, if the
whole soul holds together the whole body, we should expect each part
of the soul to hold together a part of the body. But this seems an
impossibility; it is difficult even to imagine what sort of bodily
part mind will hold together, or how it will do this.

  It is a fact of observation that plants and certain insects go on
living when divided into segments; this means that each of the
segments has a soul in it identical in species, though not numerically
identical in the different segments, for both of the segments for a
time possess the power of sensation and local movement. That this does
not last is not surprising, for they no longer possess the organs
necessary for self-maintenance. But, all the same, in each of the
bodily parts there are present all the parts of soul, and the souls so
present are homogeneous with one another and with the whole; this
means that the several parts of the soul are indisseverable from one
another, although the whole soul is divisible. It seems also that
the principle found in plants is also a kind of soul; for this is
the only principle which is common to both animals and plants; and
this exists in isolation from the principle of sensation, though there
nothing which has the latter without the former.

                              Book II

                                 1

  LET the foregoing suffice as our account of the views concerning the
soul which have been handed on by our predecessors; let us now dismiss
them and make as it were a completely fresh start, endeavouring to
give a precise answer to the question, What is soul? i.e. to formulate
the most general possible definition of it.

  We are in the habit of recognizing, as one determinate kind of
what is, substance, and that in several senses, (a) in the sense of
matter or that which in itself is not 'a this', and (b) in the sense
of form or essence, which is that precisely in virtue of which a thing
is called 'a this', and thirdly (c) in the sense of that which is
compounded of both (a) and (b). Now matter is potentiality, form
actuality; of the latter there are two grades related to one another
as e.g. knowledge to the exercise of knowledge.

  Among substances are by general consent reckoned bodies and
especially natural bodies; for they are the principles of all other
bodies. Of natural bodies some have life in them, others not; by
life we mean self-nutrition and growth (with its correlative decay).
It follows that every natural body which has life in it is a substance
in the sense of a composite.

  But since it is also a body of such and such a kind, viz. having
life, the body cannot be soul; the body is the subject or matter,
not what is attributed to it. Hence the soul must be a substance in
the sense of the form of a natural body having life potentially within
it. But substance is actuality, and thus soul is the actuality of a
body as above characterized. Now the word actuality has two senses
corresponding respectively to the possession of knowledge and the
actual exercise of knowledge. It is obvious that the soul is actuality
in the first sense, viz. that of knowledge as possessed, for both
sleeping and waking presuppose the existence of soul, and of these
waking corresponds to actual knowing, sleeping to knowledge
possessed but not employed, and, in the history of the individual,
knowledge comes before its employment or exercise.

  That is why the soul is the first grade of actuality of a natural
body having life potentially in it. The body so described is a body
which is organized. The parts of plants in spite of their extreme
simplicity are 'organs'; e.g. the leaf serves to shelter the pericarp,
the pericarp to shelter the fruit, while the roots of plants are
analogous to the mouth of animals, both serving for the absorption
of food. If, then, we have to give a general formula applicable to all
kinds of soul, we must describe it as the first grade of actuality
of a natural organized body. That is why we can wholly dismiss as
unnecessary the question whether the soul and the body are one: it
is as meaningless as to ask whether the wax and the shape given to
it by the stamp are one, or generally the matter of a thing and that
of which it is the matter. Unity has many senses (as many as 'is'
has), but the most proper and fundamental sense of both is the
relation of an actuality to that of which it is the actuality. We have
now given an answer to the question, What is soul?-an answer which
applies to it in its full extent. It is substance in the sense which
corresponds to the definitive formula of a thing's essence. That means
that it is 'the essential whatness' of a body of the character just
assigned. Suppose that what is literally an 'organ', like an axe, were
a natural body, its 'essential whatness', would have been its essence,
and so its soul; if this disappeared from it, it would have ceased
to be an axe, except in name. As it is, it is just an axe; it wants
the character which is required to make its whatness or formulable
essence a soul; for that, it would have had to be a natural body of
a particular kind, viz. one having in itself the power of setting
itself in movement and arresting itself. Next, apply this doctrine
in the case of the 'parts' of the living body. Suppose that the eye
were an animal-sight would have been its soul, for sight is the
substance or essence of the eye which corresponds to the formula,
the eye being merely the matter of seeing; when seeing is removed
the eye is no longer an eye, except in name-it is no more a real eye
than the eye of a statue or of a painted figure. We must now extend
our consideration from the 'parts' to the whole living body; for
what the departmental sense is to the bodily part which is its
organ, that the whole faculty of sense is to the whole sensitive
body as such.

  We must not understand by that which is 'potentially capable of
living' what has lost the soul it had, but only what still retains it;
but seeds and fruits are bodies which possess the qualification.
Consequently, while waking is actuality in a sense corresponding to
the cutting and the seeing, the soul is actuality in the sense
corresponding to the power of sight and the power in the tool; the
body corresponds to what exists in potentiality; as the pupil plus the
power of sight constitutes the eye, so the soul plus the body
constitutes the animal.

  From this it indubitably follows that the soul is inseparable from
its body, or at any rate that certain parts of it are (if it has
parts) for the actuality of some of them is nothing but the
actualities of their bodily parts. Yet some may be separable because
they are not the actualities of any body at all. Further, we have no
light on the problem whether the soul may not be the actuality of
its body in the sense in which the sailor is the actuality of the
ship.

  This must suffice as our sketch or outline determination of the
nature of soul.

                                 2

  Since what is clear or logically more evident emerges from what in
itself is confused but more observable by us, we must reconsider our
results from this point of view. For it is not enough for a definitive
formula to express as most now do the mere fact; it must include and
exhibit the ground also. At present definitions are given in a form
analogous to the conclusion of a syllogism; e.g. What is squaring? The
construction of an equilateral rectangle equal to a given oblong
rectangle. Such a definition is in form equivalent to a conclusion.
One that tells us that squaring is the discovery of a line which is
a mean proportional between the two unequal sides of the given
rectangle discloses the ground of what is defined.

  We resume our inquiry from a fresh starting-point by calling
attention to the fact that what has soul in it differs from what has
not, in that the former displays life. Now this word has more than one
sense, and provided any one alone of these is found in a thing we
say that thing is living. Living, that is, may mean thinking or
perception or local movement and rest, or movement in the sense of
nutrition, decay and growth. Hence we think of plants also as
living, for they are observed to possess in themselves an
originative power through which they increase or decrease in all
spatial directions; they grow up and down, and everything that grows
increases its bulk alike in both directions or indeed in all, and
continues to live so long as it can absorb nutriment.

  This power of self-nutrition can be isolated from the other powers
mentioned, but not they from it-in mortal beings at least. The fact is
obvious in plants; for it is the only psychic power they possess.

  This is the originative power the possession of which leads us to
speak of things as living at all, but it is the possession of
sensation that leads us for the first time to speak of living things
as animals; for even those beings which possess no power of local
movement but do possess the power of sensation we call animals and not
merely living things.

  The primary form of sense is touch, which belongs to all animals.
just as the power of self-nutrition can be isolated from touch and
sensation generally, so touch can be isolated from all other forms
of sense. (By the power of self-nutrition we mean that departmental
power of the soul which is common to plants and animals: all animals
whatsoever are observed to have the sense of touch.) What the
explanation of these two facts is, we must discuss later. At present
we must confine ourselves to saying that soul is the source of these
phenomena and is characterized by them, viz. by the powers of
self-nutrition, sensation, thinking, and motivity.

  Is each of these a soul or a part of a soul? And if a part, a part
in what sense? A part merely distinguishable by definition or a part
distinct in local situation as well? In the case of certain of these
powers, the answers to these questions are easy, in the case of others
we are puzzled what to say. just as in the case of plants which when
divided are observed to continue to live though removed to a
distance from one another (thus showing that in their case the soul of
each individual plant before division was actually one, potentially
many), so we notice a similar result in other varieties of soul,
i.e. in insects which have been cut in two; each of the segments
possesses both sensation and local movement; and if sensation,
necessarily also imagination and appetition; for, where there is
sensation, there is also pleasure and pain, and, where these,
necessarily also desire.

  We have no evidence as yet about mind or the power to think; it
seems to be a widely different kind of soul, differing as what is
eternal from what is perishable; it alone is capable of existence in
isolation from all other psychic powers. All the other parts of
soul, it is evident from what we have said, are, in spite of certain
statements to the contrary, incapable of separate existence though, of
course, distinguishable by definition. If opining is distinct from
perceiving, to be capable of opining and to be capable of perceiving
must be distinct, and so with all the other forms of living above
enumerated. Further, some animals possess all these parts of soul,
some certain of them only, others one only (this is what enables us to
classify animals); the cause must be considered later.' A similar
arrangement is found also within the field of the senses; some classes
of animals have all the senses, some only certain of them, others only
one, the most indispensable, touch.

  Since the expression 'that whereby we live and perceive' has two
meanings, just like the expression 'that whereby we know'-that may
mean either (a) knowledge or (b) the soul, for we can speak of knowing
by or with either, and similarly that whereby we are in health may
be either (a) health or (b) the body or some part of the body; and
since of the two terms thus contrasted knowledge or health is the name
of a form, essence, or ratio, or if we so express it an actuality of a
recipient matter-knowledge of what is capable of knowing, health of
what is capable of being made healthy (for the operation of that which
is capable of originating change terminates and has its seat in what
is changed or altered); further, since it is the soul by or with which
primarily we live, perceive, and think:-it follows that the soul
must be a ratio or formulable essence, not a matter or subject. For,
as we said, word substance has three meanings form, matter, and the
complex of both and of these three what is called matter is
potentiality, what is called form actuality. Since then the complex
here is the living thing, the body cannot be the actuality of the
soul; it is the soul which is the actuality of a certain kind of body.
Hence the rightness of the view that the soul cannot be without a
body, while it csnnot he a body; it is not a body but something
relative to a body. That is why it is in a body, and a body of a
definite kind. It was a mistake, therefore, to do as former thinkers
did, merely to fit it into a body without adding a definite
specification of the kind or character of that body. Reflection
confirms the observed fact; the actuality of any given thing can
only be realized in what is already potentially that thing, i.e. in
a matter of its own appropriate to it. From all this it follows that
soul is an actuality or formulable essence of something that possesses
a potentiality of being besouled.

                                 3

  Of the psychic powers above enumerated some kinds of living
things, as we have said, possess all, some less than all, others one
only. Those we have mentioned are the nutritive, the appetitive, the
sensory, the locomotive, and the power of thinking. Plants have none
but the first, the nutritive, while another order of living things has
this plus the sensory. If any order of living things has the
sensory, it must also have the appetitive; for appetite is the genus
of which desire, passion, and wish are the species; now all animals
have one sense at least, viz. touch, and whatever has a sense has
the capacity for pleasure and pain and therefore has pleasant and
painful objects present to it, and wherever these are present, there
is desire, for desire is just appetition of what is pleasant. Further,
all animals have the sense for food (for touch is the sense for food);
the food of all living things consists of what is dry, moist, hot,
cold, and these are the qualities apprehended by touch; all other
sensible qualities are apprehended by touch only indirectly. Sounds,
colours, and odours contribute nothing to nutriment; flavours fall
within the field of tangible qualities. Hunger and thirst are forms of
desire, hunger a desire for what is dry and hot, thirst a desire for
what is cold and moist; flavour is a sort of seasoning added to
both. We must later clear up these points, but at present it may be
enough to say that all animals that possess the sense of touch have
also appetition. The case of imagination is obscure; we must examine
it later. Certain kinds of animals possess in addition the power of
locomotion, and still another order of animate beings, i.e. man and
possibly another order like man or superior to him, the power of
thinking, i.e. mind. It is now evident that a single definition can be
given of soul only in the same sense as one can be given of figure.
For, as in that case there is no figure distinguishable and apart from
triangle, &c., so here there is no soul apart from the forms of soul
just enumerated. It is true that a highly general definition can be
given for figure which will fit all figures without expressing the
peculiar nature of any figure. So here in the case of soul and its
specific forms. Hence it is absurd in this and similar cases to demand
an absolutely general definition which will fail to express the
peculiar nature of anything that is, or again, omitting this, to
look for separate definitions corresponding to each infima species.
The cases of figure and soul are exactly parallel; for the particulars
subsumed under the common name in both cases-figures and living
beings-constitute a series, each successive term of which
potentially contains its predecessor, e.g. the square the triangle,
the sensory power the self-nutritive. Hence we must ask in the case of
each order of living things, What is its soul, i.e. What is the soul
of plant, animal, man? Why the terms are related in this serial way
must form the subject of later examination. But the facts are that the
power of perception is never found apart from the power of
self-nutrition, while-in plants-the latter is found isolated from
the former. Again, no sense is found apart from that of touch, while
touch is found by itself; many animals have neither sight, hearing,
nor smell. Again, among living things that possess sense some have the
power of locomotion, some not. Lastly, certain living beings-a small
minority-possess calculation and thought, for (among mortal beings)
those which possess calculation have all the other powers above
mentioned, while the converse does not hold-indeed some live by
imagination alone, while others have not even imagination. The mind
that knows with immediate intuition presents a different problem.

  It is evident that the way to give the most adequate definition of
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
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 builder
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
the term 'a potential sentient'. There are no separate names for the
two stages of potentiality; we have pointed out that they are
different and how they are different. We cannot help using the
incorrect terms 'being acted upon or altered' of the two transitions
involved. As we have said, has the power of sensation is potentially
like what the perceived object is actually; that is, while at the
beginning of the process of its being acted upon the two interacting
factors are dissimilar, at the end the one acted upon is assimilated
to the other and is identical in quality with it.

                                 6

  In dealing with each of the senses we shall have first to speak of
the objects which are perceptible by each. The term 'object of
sense' covers three kinds of objects, two kinds of which are, in our
language, directly perceptible, while the remaining one is only
incidentally perceptible. Of the first two kinds one (a) consists of
what is perceptible by a single sense, the other (b) of what is
perceptible by any and all of the senses. I call by the name of
special object of this or that sense that which cannot be perceived by
any other sense than that one and in respect of which no error is
possible; in this sense colour is the special object of sight, sound
of hearing, flavour of taste. Touch, indeed, discriminates more than
one set of different qualities. Each sense has one kind of object
which it discerns, and never errs in reporting that what is before
it is colour or sound (though it may err as to what it is that is
coloured or where that is, or what it is that is sounding or where
that is.) Such objects are what we propose to call the special objects
of this or that sense.

  'Common sensibles' are movement, rest, number, figure, magnitude;
these are not peculiar to any one sense, but are common to all.
There are at any rate certain kinds of movement which are
perceptible both by touch and by sight.

  We speak of an incidental object of sense where e.g. the white
object which we see is the son of Diares; here because 'being the
son of Diares' is incidental to the directly visible white patch we
speak of the son of Diares as being (incidentally) perceived or seen
by us. Because this is only incidentally an object of sense, it in
no way as such affects the senses. Of the two former kinds, both of
which are in their own nature perceptible by sense, the first
kind-that of special objects of the several senses-constitute the
objects of sense in the strictest sense of the term and it is to
them that in the nature of things the structure of each several
sense is adapted.

                            END OF PART I/II