QUESTION 76: OF THE UNION OF BODY AND SOUL
We now consider the union of the soul with the body; and concerning this
there are eight points of inquiry:
(1) Whether the intellectual principle is united to the body as its form?
(2) Whether the intellectual principle is multiplied numerically
according to the number of bodies; or is there one intelligence for all
(3) Whether in the body the form of which is an intellectual principle,
there is some other soul?
(4) Whether in the body there is any other substantial form?
(5) Of the qualities required in the body of which the intellectual
principle is the form?
(6) Whether it be united to such a body by means of another body?
(7) Whether by means of an accident?
(8) Whether the soul is wholly in each part of the body?
Article 1: Whether the intellectual principle is united to the body as its form?
Objection 1: It seems that the intellectual principle is not united to the
body as its form. For the Philosopher says (De Anima iii, 4) that the
intellect is "separate," and that it is not the act of any body.
Therefore it is not united to the body as its form.
Objection 2: Further, every form is determined according to the nature of the
matter of which it is the form; otherwise no proportion would be
required between matter and form. Therefore if the intellect were united
to the body as its form, since every body has a determinate nature, it
would follow that the intellect has a determinate nature; and thus, it
would not be capable of knowing all things, as is clear from what has
been said (Question , Article ); which is contrary to the nature of the
intellect. Therefore the intellect is not united to the body as its form.
Objection 3: Further, whatever receptive power is an act of a body, receives a
form materially and individually; for what is received must be received
according to the condition of the receiver. But the form of the thing
understood is not received into the intellect materially and
individually, but rather immaterially and universally: otherwise the
intellect would not be capable of the knowledge of immaterial and
universal objects, but only of individuals, like the senses. Therefore
the intellect is not united to the body as its form.
Objection 4: Further, power and action have the same subject; for the same
subject is what can, and does, act. But the intellectual action is not
the action of a body, as appears from above (Question , Article ). Therefore
neither is the intellectual faculty a power of the body. But virtue or
power cannot be more abstract or more simple than the essence from which
the faculty or power is derived. Therefore neither is the substance of
the intellect the form of a body.
Objection 5: Further, whatever has "per se" existence is not united to the
body as its form; because a form is that by which a thing exists: so that
the very existence of a form does not belong to the form by itself. But
the intellectual principle has "per se" existence and is subsistent, as
was said above (Question , Article ). Therefore it is not united to the body as
Objection 6: Further, whatever exists in a thing by reason of its nature
exists in it always. But to be united to matter belongs to the form by
reason of its nature; because form is the act of matter, not by an
accidental quality, but by its own essence; otherwise matter and form
would not make a thing substantially one, but only accidentally one.
Therefore a form cannot be without its own proper matter. But the
intellectual principle, since it is incorruptible, as was shown above
(Question , Article ), remains separate from the body, after the dissolution of
the body. Therefore the intellectual principle is not united to the body
as its form.
On the contrary, According to the Philosopher, Metaph. viii (Did. vii
2), difference is derived from the form. But the difference which
constitutes man is "rational," which is applied to man on account of his
intellectual principle. Therefore the intellectual principle is the form
I answer that, We must assert that the intellect which is the principle
of intellectual operation is the form of the human body. For that whereby
primarily anything acts is a form of the thing to which the act is to be
attributed: for instance, that whereby a body is primarily healed is
health, and that whereby the soul knows primarily is knowledge; hence
health is a form of the body, and knowledge is a form of the soul. The
reason is because nothing acts except so far as it is in act; wherefore a
thing acts by that whereby it is in act. Now it is clear that the first
thing by which the body lives is the soul. And as life appears through
various operations in different degrees of living things, that whereby we
primarily perform each of all these vital actions is the soul. For the
soul is the primary principle of our nourishment, sensation, and local
movement; and likewise of our understanding. Therefore this principle by
which we primarily understand, whether it be called the intellect or the
intellectual soul, is the form of the body. This is the demonstration
used by Aristotle (De Anima ii, 2).
But if anyone says that the intellectual soul is not the form of the
body he must first explain how it is that this action of understanding is
the action of this particular man; for each one is conscious that it is
himself who understands. Now an action may be attributed to anyone in
three ways, as is clear from the Philosopher (Phys. v, 1); for a thing is
said to move or act, either by virtue of its whole self, for instance, as
a physician heals; or by virtue of a part, as a man sees by his eye; or
through an accidental quality, as when we say that something that is
white builds, because it is accidental to the builder to be white. So
when we say that Socrates or Plato understands, it is clear that this is
not attributed to him accidentally; since it is ascribed to him as man,
which is predicated of him essentially. We must therefore say either that
Socrates understands by virtue of his whole self, as Plato maintained,
holding that man is an intellectual soul; or that intelligence is a part
of Socrates. The first cannot stand, as was shown above (Question , Article ),
for this reason, that it is one and the same man who is conscious both
that he understands, and that he senses. But one cannot sense without a
body: therefore the body must be some part of man. It follows therefore
that the intellect by which Socrates understands is a part of Socrates,
so that in some way it is united to the body of Socrates.
The Commentator held that this union is through the intelligible
species, as having a double subject, in the possible intellect, and in
the phantasms which are in the corporeal organs. Thus through the
intelligible species the possible intellect is linked to the body of this
or that particular man. But this link or union does not sufficiently
explain the fact, that the act of the intellect is the act of Socrates.
This can be clearly seen from comparison with the sensitive faculty, from
which Aristotle proceeds to consider things relating to the intellect.
For the relation of phantasms to the intellect is like the relation of
colors to the sense of sight, as he says De Anima iii, 5,7. Therefore, as
the species of colors are in the sight, so are the species of phantasms
in the possible intellect. Now it is clear that because the colors, the
images of which are in the sight, are on a wall, the action of seeing is
not attributed to the wall: for we do not say that the wall sees, but
rather that it is seen. Therefore, from the fact that the species of
phantasms are in the possible intellect, it does not follow that
Socrates, in whom are the phantasms, understands, but that he or his
phantasms are understood.
Some, however, tried to maintain that the intellect is united to the
body as its motor; and hence that the intellect and body form one thing
so that the act of the intellect could be attributed to the whole. This
is, however, absurd for many reasons. First, because the intellect does
not move the body except through the appetite, the movement of which
presupposes the operation of the intellect. The reason therefore why
Socrates understands is not because he is moved by his intellect, but
rather, contrariwise, he is moved by his intellect because he
understands. Secondly, because since Socrates is an individual in a
nature of one essence composed of matter and form, if the intellect be
not the form, it follows that it must be outside the essence, and then
the intellect is the whole Socrates as a motor to the thing moved.
Whereas the act of intellect remains in the agent, and does not pass into
something else, as does the action of heating. Therefore the action of
understanding cannot be attributed to Socrates for the reason that he is
moved by his intellect. Thirdly, because the action of a motor is never
attributed to the thing moved, except as to an instrument; as the action
of a carpenter to a saw. Therefore if understanding is attributed to
Socrates, as the action of what moves him, it follows that it is
attributed to him as to an instrument. This is contrary to the teaching
of the Philosopher, who holds that understanding is not possible through
a corporeal instrument (De Anima iii, 4). Fourthly, because, although the
action of a part be attributed to the whole, as the action of the eye is
attributed to a man; yet it is never attributed to another part, except
perhaps indirectly; for we do not say that the hand sees because the eye
sees. Therefore if the intellect and Socrates are united in the above
manner, the action of the intellect cannot be attributed to Socrates. If,
however, Socrates be a whole composed of a union of the intellect with
whatever else belongs to Socrates, and still the intellect be united to
those other things only as a motor, it follows that Socrates is not one
absolutely, and consequently neither a being absolutely, for a thing is a
being according as it is one.
There remains, therefore, no other explanation than that given by
Aristotle---namely, that this particular man understands, because the
intellectual principle is his form. Thus from the very operation of the
intellect it is made clear that the intellectual principle is united to
the body as its form.
The same can be clearly shown from the nature of the human species. For
the nature of each thing is shown by its operation. Now the proper
operation of man as man is to understand; because he thereby surpasses
all other animals. Whence Aristotle concludes (Ethic. x, 7) that the
ultimate happiness of man must consist in this operation as properly
belonging to him. Man must therefore derive his species from that which
is the principle of this operation. But the species of anything is
derived from its form. It follows therefore that the intellectual
principle is the proper form of man.
But we must observe that the nobler a form is, the more it rises above
corporeal matter, the less it is merged in matter, and the more it excels
matter by its power and its operation; hence we find that the form of a
mixed body has another operation not caused by its elemental qualities.
And the higher we advance in the nobility of forms, the more we find that
the power of the form excels the elementary matter; as the vegetative
soul excels the form of the metal, and the sensitive soul excels the
vegetative soul. Now the human soul is the highest and noblest of forms.
Wherefore it excels corporeal matter in its power by the fact that it has
an operation and a power in which corporeal matter has no share whatever.
This power is called the intellect.
It is well to remark that if anyone holds that the soul is composed of
matter and form, it would follow that in no way could the soul be the
form of the body. For since the form is an act, and matter is only in
potentiality, that which is composed of matter and form cannot be the
form of another by virtue of itself as a whole. But if it is a form by
virtue of some part of itself, then that part which is the form we call
the soul, and that of which it is the form we call the "primary animate,"
as was said above (Question , Article ).
Reply to Objection 1: As the Philosopher says (Phys. ii, 2), the ultimate natural
form to which the consideration of the natural philosopher is directed is
indeed separate; yet it exists in matter. He proves this from the fact
that "man and the sun generate man from matter." It is separate indeed
according to its intellectual power, because the intellectual power does
not belong to a corporeal organ, as the power of seeing is the act of the
eye; for understanding is an act which cannot be performed by a corporeal
organ, like the act of seeing. But it exists in matter so far as the soul
itself, to which this power belongs, is the form of the body, and the
term of human generation. And so the Philosopher says (De Anima iii) that
the intellect is separate, because it is not the faculty of a corporeal
From this it is clear how to answer the Second and Third objections:
since, in order that man may be able to understand all things by means of
his intellect, and that his intellect may understand immaterial things
and universals, it is sufficient that the intellectual power be not the
act of the body.
Reply to Objection 4: The human soul, by reason of its perfection, is not a form
merged in matter, or entirely embraced by matter. Therefore there is
nothing to prevent some power thereof not being the act of the body,
although the soul is essentially the form of the body.
Reply to Objection 5: The soul communicates that existence in which it subsists
to the corporeal matter, out of which and the intellectual soul there
results unity of existence; so that the existence of the whole composite
is also the existence of the soul. This is not the case with other
non-subsistent forms. For this reason the human soul retains its own
existence after the dissolution of the body; whereas it is not so with
Reply to Objection 6: To be united to the body belongs to the soul by reason of
itself, as it belongs to a light body by reason of itself to be raised
up. And as a light body remains light, when removed from its proper
place, retaining meanwhile an aptitude and an inclination for its proper
place; so the human soul retains its proper existence when separated from
the body, having an aptitude and a natural inclination to be united to
Article 2: Whether the intellectual principle is multiplied according to the number of bodies?
Objection 1: It would seem that the intellectual principle is not multiplied
according to the number of bodies, but that there is one intellect in all
men. For an immaterial substance is not multiplied in number within one
species. But the human soul is an immaterial substance; since it is not
composed of matter and form as was shown above (Question , Article ). Therefore
there are not many human souls in one species. But all men are of one
species. Therefore there is but one intellect in all men.
Objection 2: Further, when the cause is removed, the effect is also removed.
Therefore, if human souls were multiplied according to the number of
bodies, it follows that the bodies being removed, the number of souls
would not remain; but from all the souls there would be but a single
remainder. This is heretical; for it would do away with the distinction
of rewards and punishments.
Objection 3: Further, if my intellect is distinct from your intellect, my
intellect is an individual, and so is yours; for individuals are things
which differ in number but agree in one species. Now whatever is received
into anything must be received according to the condition of the
receiver. Therefore the species of things would be received individually
into my intellect, and also into yours: which is contrary to the nature
of the intellect which knows universals.
Objection 4: Further, the thing understood is in the intellect which
understands. If, therefore, my intellect is distinct from yours, what is
understood by me must be distinct from what is understood by you; and
consequently it will be reckoned as something individual, and be only
potentially something understood; so that the common intention will have
to be abstracted from both; since from things diverse something
intelligible common to them may be abstracted. But this is contrary to
the nature of the intellect; for then the intellect would seem not to be
distinct from the imagination. It seems, therefore, to follow that there
is one intellect in all men.
Objection 5: Further, when the disciple receives knowledge from the master, it
cannot be said that the master's knowledge begets knowledge in the
disciple, because then also knowledge would be an active form, such as
heat is, which is clearly false. It seems, therefore, that the same
individual knowledge which is in the master is communicated to the
disciple; which cannot be, unless there is one intellect in both.
Seemingly, therefore, the intellect of the disciple and master is but
one; and, consequently, the same applies to all men.
Objection 6: Further, Augustine (De Quant. Animae xxxii) says: "If I were to
say that there are many human souls, I should laugh at myself." But the
soul seems to be one chiefly on account of the intellect. Therefore there
is one intellect of all men.
On the contrary, The Philosopher says (Phys. ii, 3) that the relation of
universal causes to universals is like the relation of particular causes
to individuals. But it is impossible that a soul, one in species, should
belong to animals of different species. Therefore it is impossible that
one individual intellectual soul should belong to several individuals.
I answer that, It is absolutely impossible for one intellect to belong
to all men. This is clear if, as Plato maintained, man is the intellect
itself. For it would follow that Socrates and Plato are one man; and that
they are not distinct from each other, except by something outside the
essence of each. The distinction between Socrates and Plato would be no
other than that of one man with a tunic and another with a cloak; which
is quite absurd.
It is likewise clear that this is impossible if, according to the
opinion of Aristotle (De Anima ii, 2), it is supposed that the intellect
is a part or a power of the soul which is the form of man. For it is
impossible for many distinct individuals to have one form, as it is
impossible for them to have one existence, for the form is the principle
Again, this is clearly impossible, whatever one may hold as to the
manner of the union of the intellect to this or that man. For it is
manifest that, supposing there is one principal agent, and two
instruments, we can say that there is one agent absolutely, but several
actions; as when one man touches several things with his two hands, there
will be one who touches, but two contacts. If, on the contrary, we
suppose one instrument and several principal agents, we might say that
there are several agents, but one act; for example, if there be many
drawing a ship by means of a rope; there will be many drawing, but one
pull. If, however, there is one principal agent, and one instrument, we
say that there is one agent and one action, as when the smith strikes
with one hammer, there is one striker and one stroke. Now it is clear
that no matter how the intellect is united or coupled to this or that
man, the intellect has the precedence of all the other things which
appertain to man; for the sensitive powers obey the intellect, and are at
its service. Therefore, if we suppose two men to have several intellects
and one sense---for instance, if two men had one eye---there would be
several seers, but one sight. But if there is one intellect, no matter
how diverse may be all those things of which the intellect makes use as
instruments, in no way is it possible to say that Socrates and Plato are
otherwise than one understanding man. And if to this we add that to
understand, which is the act of the intellect, is not affected by any
organ other than the intellect itself; it will further follow that there
is but one agent and one action: that is to say that all men are but one
"understander," and have but one act of understanding, in regard, that
is, of one intelligible object.
However, it would be possible to distinguish my intellectual action form
yours by the distinction of the phantasms---that is to say, were there
one phantasm of a stone in me, and another in you---if the phantasm
itself, as it is one thing in me and another in you, were a form of the
possible intellect; since the same agent according to divers forms
produces divers actions; as, according to divers forms of things with
regard to the same eye, there are divers visions. But the phantasm itself
is not a form of the possible intellect; it is the intelligible species
abstracted from the phantasm that is a form. Now in one intellect, from
different phantasms of the same species, only one intelligible species is
abstracted; as appears in one man, in whom there may be different
phantasms of a stone; yet from all of them only one intelligible species
of a stone is abstracted; by which the intellect of that one man, by one
operation, understands the nature of a stone, notwithstanding the
diversity of phantasms. Therefore, if there were one intellect for all
men, the diversity of phantasms which are in this one and that one would
not cause a diversity of intellectual operation in this man and that man.
It follows, therefore, that it is altogether impossible and unreasonable
to maintain that there exists one intellect for all men.
Reply to Objection 1: Although the intellectual soul, like an angel, has no
matter from which it is produced, yet it is the form of a certain matter;
in which it is unlike an angel. Therefore, according to the division of
matter, there are many souls of one species; while it is quite impossible
for many angels to be of one species.
Reply to Objection 2: Everything has unity in the same way that it has being;
consequently we must judge of the multiplicity of a thing as we judge of
its being. Now it is clear that the intellectual soul, by virtue of its
very being, is united to the body as its form; yet, after the dissolution
of the body, the intellectual soul retains its own being. In like manner
the multiplicity of souls is in proportion to the multiplicity of the
bodies; yet, after the dissolution of the bodies, the souls retain their
Reply to Objection 3: Individuality of the intelligent being, or of the species
whereby it understands, does not exclude the understanding of universals;
otherwise, since separate intellects are subsistent substances, and
consequently individual, they could not understand universals. But the
materiality of the knower, and of the species whereby it knows, impedes
the knowledge of the universal. For as every action is according to the
mode of the form by which the agent acts, as heating is according to the
mode of the heat; so knowledge is according to the mode of the species by
which the knower knows. Now it is clear that common nature becomes
distinct and multiplied by reason of the individuating principles which
come from the matter. Therefore if the form, which is the means of
knowledge, is material---that is, not abstracted from material
conditions---its likeness to the nature of a species or genus will be
according to the distinction and multiplication of that nature by means
of individuating principles; so that knowledge of the nature of a thing
in general will be impossible. But if the species be abstracted from the
conditions of individual matter, there will be a likeness of the nature
without those things which make it distinct and multiplied; thus there
will be knowledge of the universal. Nor does it matter, as to this
particular point, whether there be one intellect or many; because, even
if there were but one, it would necessarily be an individual intellect,
and the species whereby it understands, an individual species.
Reply to Objection 4: Whether the intellect be one or many, what is understood is
one; for what is understood is in the intellect, not according to its own
nature, but according to its likeness; for "the stone is not in the soul,
but its likeness is," as is said, De Anima iii, 8. Yet it is the stone
which is understood, not the likeness of the stone; except by a
reflection of the intellect on itself: otherwise, the objects of sciences
would not be things, but only intelligible species. Now it happens that
different things, according to different forms, are likened to the same
thing. And since knowledge is begotten according to the assimilation of
the knower to the thing known, it follows that the same thing may happen
to be known by several knowers; as is apparent in regard to the senses;
for several see the same color, according to different likenesses. In the
same way several intellects understand one object understood. But there
is this difference, according to the opinion of Aristotle, between the
sense and the intelligence---that a thing is perceived by the sense
according to the disposition which it has outside the soul ---that is, in
its individuality; whereas the nature of the thing understood is indeed
outside the soul, but the mode according to which it exists outside the
soul is not the mode according to which it is understood. For the common
nature is understood as apart from the individuating principles; whereas
such is not its mode of existence outside the soul. But, according to the
opinion of Plato, the thing understood exists outside the soul in the
same condition as those under which it is understood; for he supposed
that the natures of things exist separate from matter.
Reply to Objection 6: Augustine denies a plurality of souls, that would involve a
plurality of species.
Article 3: Whether besides the intellectual soul there are in man other souls essentially different from one another?
Objection 1: It would seem that besides the intellectual soul there are in man
other souls essentially different from one another, such as the sensitive
soul and the nutritive soul. For corruptible and incorruptible are not of
the same substance. But the intellectual soul is incorruptible; whereas
the other souls, as the sensitive and the nutritive, are corruptible, as
was shown above (Question , Article ). Therefore in man the essence of the
intellectual soul, the sensitive soul, and the nutritive soul, cannot be
Objection 2: Further, if it be said that the sensitive soul in man is
incorruptible; on the contrary, "corruptible and incorruptible differ
generically," says the Philosopher, Metaph. x (Did. ix, 10). But the
sensitive soul in the horse, the lion, and other brute animals, is
corruptible. If, therefore, in man it be incorruptible, the sensitive
soul in man and brute animals will not be of the same "genus." Now an
animal is so called from its having a sensitive soul; and, therefore,
"animal" will not be one genus common to man and other animals, which is
Objection 3: Further, the Philosopher says, Metaph. viii (Did. vii, 2), that
the genus is taken from the matter, and difference from the form. But
"rational," which is the difference constituting man, is taken from the
intellectual soul; while he is called "animal" by reason of his having a
body animated by a sensitive soul. Therefore the intellectual soul may be
compared to the body animated by a sensitive soul, as form to matter.
Therefore in man the intellectual soul is not essentially the same as the
sensitive soul, but presupposes it as a material subject.
On the contrary, It is said in the book De Ecclesiasticis Dogmatibus xv:
"Nor do we say that there are two souls in one man, as James and other
Syrians write; one, animal, by which the body is animated, and which is
mingled with the blood; the other, spiritual, which obeys the reason; but
we say that it is one and the same soul in man, that both gives life to
the body by being united to it, and orders itself by its own reasoning."
I answer that, Plato held that there were several souls in one body,
distinct even as to organs, to which souls he referred the different
vital actions, saying that the nutritive power is in the liver, the
concupiscible in the heart, and the power of knowledge in the brain.
Which opinion is rejected by Aristotle (De Anima ii, 2), with regard to
those parts of the soul which use corporeal organs; for this reason, that
in those animals which continue to live when they have been divided in
each part are observed the operations of the soul, as sense and appetite.
Now this would not be the case if the various principles of the soul's
operations were essentially different, and distributed in the various
parts of the body. But with regard to the intellectual part, he seems to
leave it in doubt whether it be "only logically" distinct from the other
parts of the soul, "or also locally."
The opinion of Plato might be maintained if, as he held, the soul was
supposed to be united to the body, not as its form, but as its motor. For
it involves nothing unreasonable that the same movable thing be moved by
several motors; and still less if it be moved according to its various
parts. If we suppose, however, that the soul is united to the body as its
form, it is quite impossible for several essentially different souls to
be in one body. This can be made clear by three different reasons.
In the first place, an animal would not be absolutely one, in which
there were several souls. For nothing is absolutely one except by one
form, by which a thing has existence: because a thing has from the same
source both existence and unity; and therefore things which are
denominated by various forms are not absolutely one; as, for instance, "a
white man." If, therefore, man were 'living' by one form, the vegetative
soul, and 'animal' by another form, the sensitive soul, and "man" by
another form, the intellectual soul, it would follow that man is not
absolutely one. Thus Aristotle argues, Metaph. viii (Did. vii, 6),
against Plato, that if the idea of an animal is distinct from the idea of
a biped, then a biped animal is not absolutely one. For this reason,
against those who hold that there are several souls in the body, he asks
(De Anima i, 5), "what contains them?"---that is, what makes them one? It
cannot be said that they are united by the one body; because rather does
the soul contain the body and make it one, than the reverse.
Secondly, this is proved to be impossible by the manner in which one
thing is predicated of another. Those things which are derived from
various forms are predicated of one another, either accidentally, (if the
forms are not ordered to one another, as when we say that something white
is sweet), or essentially, in the second manner of essential predication,
(if the forms are ordered one to another, the subject belonging to the
definition of the predicate; as a surface is presupposed to color; so
that if we say that a body with a surface is colored, we have the second
manner of essential predication.) Therefore, if we have one form by which
a thing is an animal, and another form by which it is a man, it follows
either that one of these two things could not be predicated of the other,
except accidentally, supposing these two forms not to be ordered to one
another---or that one would be predicated of the other according to the
second manner of essential predication, if one soul be presupposed to the
other. But both of these consequences are clearly false: because "animal"
is predicated of man essentially and not accidentally; and man is not
part of the definition of an animal, but the other way about. Therefore
of necessity by the same form a thing is animal and man; otherwise man
would not really be the thing which is an animal, so that animal can be
essentially predicated of man.
Thirdly, this is shown to be impossible by the fact that when one
operation of the soul is intense it impedes another, which could never be
the case unless the principle of action were essentially one.
We must therefore conclude that in man the sensitive soul, the
intellectual soul, and the nutritive soul are numerically one soul. This
can easily be explained, if we consider the differences of species and
forms. For we observe that the species and forms of things differ from
one another, as the perfect and imperfect; as in the order of things, the
animate are more perfect than the inanimate, and animals more perfect
than plants, and man than brute animals; and in each of these genera
there are various degrees. For this reason Aristotle, Metaph. viii (Did.
vii, 3), compares the species of things to numbers, which differ in
species by the addition or subtraction of unity. And (De Anima ii, 3) he
compares the various souls to the species of figures, one of which
contains another; as a pentagon contains and exceeds a tetragon. Thus the
intellectual soul contains virtually whatever belongs to the sensitive
soul of brute animals, and to the nutritive souls of plants. Therefore,
as a surface which is of a pentagonal shape, is not tetragonal by one
shape, and pentagonal by another---since a tetragonal shape would be
superfluous as contained in the pentagonal---so neither is Socrates a man
by one soul, and animal by another; but by one and the same soul he is
both animal and man.
Reply to Objection 1: The sensitive soul is incorruptible, not by reason of its
being sensitive, but by reason of its being intellectual. When,
therefore, a soul is sensitive only, it is corruptible; but when with
sensibility it has also intellectuality, it is incorruptible. For
although sensibility does not give incorruptibility, yet it cannot
deprive intellectuality of its incorruptibility.
Reply to Objection 2: Not forms, but composites, are classified either
generically or specifically. Now man is corruptible like other animals.
And so the difference of corruptible and incorruptible which is on the
part of the forms does not involve a generic difference between man and
the other animals.
Reply to Objection 3: The embryo has first of all a soul which is merely
sensitive, and when this is removed, it is supplanted by a more perfect
soul, which is both sensitive and intellectual: as will be shown further
on (Question , Article , ad 2).
Reply to Objection 4: We must not consider the diversity of natural things as
proceeding from the various logical notions or intentions, which flow
from our manner of understanding, because reason can apprehend one and
the same thing in various ways. Therefore since, as we have said, the
intellectual soul contains virtually what belongs to the sensitive soul,
and something more, reason can consider separately what belongs to the
power of the sensitive soul, as something imperfect and material. And
because it observes that this is something common to man and to other
animals, it forms thence the notion of the "genus"; while that wherein
the intellectual soul exceeds the sensitive soul, it takes as formal and
perfecting; thence it gathers the "difference" of man.
Article 4: Whether in man there is another form besides the intellectual soul?
Objection 1: It would seem that in man there is another form besides the
intellectual soul. For the Philosopher says (De Anima ii, 1), that "the
soul is the act of a physical body which has life potentially." Therefore
the soul is to the body as a form of matter. But the body has a
substantial form by which it is a body. Therefore some other substantial
form in the body precedes the soul.
Objection 2: Further, man moves himself as every animal does. Now everything
that moves itself is divided into two parts, of which one moves, and the
other is moved, as the Philosopher proves (Phys. viii, 5). But the part
which moves is the soul. Therefore the other part must be such that it
can be moved. But primary matter cannot be moved (Phys. v, 1), since it
is a being only potentially; indeed everything that is moved is a body.
Therefore in man and in every animal there must be another substantial
form, by which the body is constituted.
Objection 3: Further, the order of forms depends on their relation to primary
matter; for "before" and "after" apply by comparison to some beginning.
Therefore if there were not in man some other substantial form besides
the rational soul, and if this were to inhere immediately to primary
matter; it would follow that it ranks among the most imperfect forms
which inhere to matter immediately.
Objection 4: Further, the human body is a mixed body. Now mingling does not
result from matter alone; for then we should have mere corruption.
Therefore the forms of the elements must remain in a mixed body; and
these are substantial forms. Therefore in the human body there are other
substantial forms besides the intellectual soul.
On the contrary, Of one thing there is but one substantial being. But
the substantial form gives substantial being. Therefore of one thing
there is but one substantial form. But the soul is the substantial form
of man. Therefore it is impossible for there to be in man another
substantial form besides the intellectual soul.
I answer that, If we suppose that the intellectual soul is not united to
the body as its form, but only as its motor, as the Platonists maintain,
it would necessarily follow that in man there is another substantial
form, by which the body is established in its being as movable by the
soul. If, however, the intellectual soul be united to the body as its
substantial form, as we have said above (Article ), it is impossible for
another substantial form besides the intellectual soul to be found in
In order to make this evident, we must consider that the substantial
form differs from the accidental form in this, that the accidental form
does not make a thing to be "simply," but to be "such," as heat does not
make a thing to be simply, but only to be hot. Therefore by the coming of
the accidental form a thing is not said to be made or generated simply,
but to be made such, or to be in some particular condition; and in like
manner, when an accidental form is removed, a thing is said to be
corrupted, not simply, but relatively. Now the substantial form gives
being simply; therefore by its coming a thing is said to be generated
simply; and by its removal to be corrupted simply. For this reason, the
old natural philosophers, who held that primary matter was some actual
being---for instance, fire or air, or something of that sort---maintained
that nothing is generated simply, or corrupted simply; and stated that
"every becoming is nothing but an alteration," as we read, Phys. i, 4.
Therefore, if besides the intellectual soul there pre-existed in matter
another substantial form by which the subject of the soul were made an
actual being, it would follow that the soul does not give being simply;
and consequently that it is not the substantial form: and so at the
advent of the soul there would not be simple generation; nor at its
removal simple corruption, all of which is clearly false.
Whence we must conclude, that there is no other substantial form in man
besides the intellectual soul; and that the soul, as it virtually
contains the sensitive and nutritive souls, so does it virtually contain
all inferior forms, and itself alone does whatever the imperfect forms do
in other things. The same is to be said of the sensitive soul in brute
animals, and of the nutritive soul in plants, and universally of all more
perfect forms with regard to the imperfect.
Reply to Objection 1: Aristotle does not say that the soul is the act of a body
only, but "the act of a physical organic body which has life
potentially"; and that this potentiality "does not reject the soul."
Whence it is clear that when the soul is called the act, the soul itself
is included; as when we say that heat is the act of what is hot, and
light of what is lucid; not as though lucid and light were two separate
things, but because a thing is made lucid by the light. In like manner,
the soul is said to be the "act of a body," etc., because by the soul it
is a body, and is organic, and has life potentially. Yet the first act is
said to be in potentiality to the second act, which is operation; for
such a potentiality "does not reject"---that is, does not exclude---the
Reply to Objection 2: The soul does not move the body by its essence, as the form
of the body, but by the motive power, the act of which presupposes the
body to be already actualized by the soul: so that the soul by its motive
power is the part which moves; and the animate body is the part moved.
Reply to Objection 3: We observe in matter various degrees of perfection, as
existence, living, sensing, and understanding. Now what is added is
always more perfect. Therefore that form which gives matter only the
first degree of perfection is the most imperfect; while that form which
gives the first, second, and third degree, and so on, is the most
perfect: and yet it inheres to matter immediately.
Reply to Objection 4: Avicenna held that the substantial forms of the elements
remain entire in the mixed body; and that the mixture is made by the
contrary qualities of the elements being reduced to an average. But this
is impossible, because the various forms of the elements must necessarily
be in various parts of matter; for the distinction of which we must
suppose dimensions, without which matter cannot be divisible. Now matter
subject to dimension is not to be found except in a body. But various
bodies cannot be in the same place. Whence it follows that elements in
the mixed body would be distinct as to situation. And then there would
not be a real mixture which is in respect of the whole; but only a
mixture apparent to sense, by the juxtaposition of particles.
Averroes maintained that the forms of elements, by reason of their
imperfection, are a medium between accidental and substantial forms, and
so can be "more" or "less"; and therefore in the mixture they are
modified and reduced to an average, so that one form emerges from them.
But this is even still more impossible. For the substantial being of each
thing consists in something indivisible, and every addition and
subtraction varies the species, as in numbers, as stated in Metaph. viii
(Did. vii, 3); and consequently it is impossible for any substantial form
to receive "more" or "less." Nor is it less impossible for anything to be
a medium between substance and accident.
Therefore we must say, in accordance with the Philosopher (De Gener. i,
10), that the forms of the elements remain in the mixed body, not
actually but virtually. For the proper qualities of the elements remain,
though modified; and in them is the power of the elementary forms. This
quality of the mixture is the proper disposition for the substantial form
of the mixed body; for instance, the form of a stone, or of any sort of
Article 5: Whether the intellectual soul is properly united to such a body?
Objection 1: It would seem that the intellectual soul is improperly united to
such a body. For matter must be proportionate to the form. But the
intellectual soul is incorruptible. Therefore it is not properly united
to a corruptible body.
Objection 2: Further, the intellectual soul is a perfectly immaterial form; a
proof whereof is its operation in which corporeal matter does not share.
But the more subtle is the body, the less has it of matter. Therefore the
soul should be united to a most subtle body, to fire, for instance, and
not to a mixed body, still less to a terrestrial body.
Objection 3: Further, since the form is the principle of the species, one form
cannot produce a variety of species. But the intellectual soul is one
form. Therefore, it should not be united to a body which is composed of
parts belonging to various species.
Objection 4: Further, what is susceptible of a more perfect form should itself
be more perfect. But the intellectual soul is the most perfect of souls.
Therefore since the bodies of other animals are naturally provided with a
covering, for instance, with hair instead of clothes, and hoofs instead
of shoes; and are, moreover, naturally provided with arms, as claws,
teeth, and horns; it seems that the intellectual soul should not have
been united to a body which is imperfect as being deprived of the above
means of protection.
On the contrary, The Philosopher says (De Anima ii, 1), that "the soul
is the act of a physical organic body having life potentially."
I answer that, Since the form is not for the matter, but rather the
matter for the form, we must gather from the form the reason why the
matter is such as it is; and not conversely. Now the intellectual soul,
as we have seen above (Question , Article ) in the order of nature, holds the
lowest place among intellectual substances; inasmuch as it is not
naturally gifted with the knowledge of truth, as the angels are; but has
to gather knowledge from individual things by way of the senses, as
Dionysius says (Div. Nom. vii). But nature never fails in necessary
things: therefore the intellectual soul had to be endowed not only with
the power of understanding, but also with the power of feeling. Now the
action of the senses is not performed without a corporeal instrument.
Therefore it behooved the intellectual soul to be united to a body fitted
to be a convenient organ of sense.
Now all the other senses are based on the sense of touch. But the organ
of touch requires to be a medium between contraries, such as hot and
cold, wet and dry, and the like, of which the sense of touch has the
perception; thus it is in potentiality with regard to contraries, and is
able to perceive them. Therefore the more the organ of touch is reduced
to an equable complexion, the more sensitive will be the touch. But the
intellectual soul has the power of sense in all its completeness; because
what belongs to the inferior nature pre-exists more perfectly in the
superior, as Dionysius says (Div. Nom. v). Therefore the body to which
the intellectual soul is united should be a mixed body, above others
reduced to the most equable complexion. For this reason among animals,
man has the best sense of touch. And among men, those who have the best
sense of touch have the best intelligence. A sign of which is that we
observe "those who are refined in body are well endowed in mind," as
stated in De Anima ii, 9.
Reply to Objection 1: Perhaps someone might attempt to answer this by saying
that before sin the human body was incorruptible. This answer does not
seem sufficient; because before sin the human body was immortal not by
nature, but by a gift of Divine grace; otherwise its immortality would
not be forfeited through sin, as neither was the immortality of the devil.
Therefore we answer otherwise by observing that in matter two conditions
are to be found; one which is chosen in order that the matter be suitable
to the form; the other which follows by force of the first disposition.
The artisan, for instance, for the form of the saw chooses iron adapted
for cutting through hard material; but that the teeth of the saw may
become blunt and rusted, follows by force of the matter itself. So the
intellectual soul requires a body of equable complexion, which, however,
is corruptible by force of its matter. If, however, it be said that God
could avoid this, we answer that in the formation of natural things we do
not consider what God might do; but what is suitable to the nature of
things, as Augustine says (Gen. ad lit. ii, 1). God, however, provided in
this case by applying a remedy against death in the gift of grace.
Reply to Objection 2: A body is not necessary to the intellectual soul by reason
of its intellectual operation considered as such; but on account of the
sensitive power, which requires an organ of equable temperament.
Therefore the intellectual soul had to be united to such a body, and not
to a simple element, or to a mixed body, in which fire was in excess;
because otherwise there could not be an equability of temperament. And
this body of an equable temperament has a dignity of its own by reason of
its being remote from contraries, thereby resembling in a way a heavenly
Reply to Objection 3: The parts of an animal, for instance, the eye, hand, flesh,
and bones, and so forth, do not make the species; but the whole does, and
therefore, properly speaking, we cannot say that these are of different
species, but that they are of various dispositions. This is suitable to
the intellectual soul, which, although it be one in its essence, yet on
account of its perfection, is manifold in power: and therefore, for its
various operations it requires various dispositions in the parts of the
body to which it is united. For this reason we observe that there is a
greater variety of parts in perfect than in imperfect animals; and in
these a greater variety than in plants.
Reply to Objection 4: The intellectual soul as comprehending universals, has a
power extending to the infinite; therefore it cannot be limited by nature
to certain fixed natural notions, or even to certain fixed means whether
of defence or of clothing, as is the case with other animals, the souls
of which are endowed with knowledge and power in regard to fixed
particular things. Instead of all these, man has by nature his reason and
his hands, which are "the organs of organs" (De Anima iii), since by
their means man can make for himself instruments of an infinite variety,
and for any number of purposes.
Article 6: Whether the intellectual soul is united to the body through the medium of accidental dispositions?
Objection 1: It would seem that the intellectual soul is united to the body
through the medium of accidental dispositions. For every form exists in
its proper disposed matter. But dispositions to a form are accidents.
Therefore we must presuppose accidents to be in matter before the
substantial form; and therefore before the soul, since the soul is a
Objection 2: Further, various forms of one species require various parts of
matter. But various parts of matter are unintelligible without division
in measurable quantities. Therefore we must suppose dimensions in matter
before the substantial forms, which are many belonging to one species.
Objection 3: Further, what is spiritual is connected with what is corporeal by
virtual contact. But the virtue of the soul is its power. Therefore it
seems that the soul is united to the body by means of a power, which is
On the contrary, Accident is posterior to substance, both in the order
of time and in the order of reason, as the Philosopher says, Metaph. vii
(Did. vi, 1). Therefore it is unintelligible that any accidental form
exist in matter before the soul, which is the substantial form.
I answer that, If the soul were united to the body, merely as a motor,
there would be nothing to prevent the existence of certain dispositions
mediating between the soul and the body; on the contrary, they would be
necessary, for on the part of the soul would be required the power to
move the body; and on the part of the body, a certain aptitude to be
moved by the soul.
If, however, the intellectual soul is united to the body as the
substantial form, as we have already said above (Article ), it is impossible
for any accidental disposition to come between the body and the soul, or
between any substantial form whatever and its matter. The reason is
because since matter is in potentiality to all manner of acts in a
certain order, what is absolutely first among the acts must be understood
as being first in matter. Now the first among all acts is existence.
Therefore, it is impossible for matter to be apprehended as hot, or as
having quantity, before it is actual. But matter has actual existence by
the substantial form, which makes it to exist absolutely, as we have said
above (Article ). Wherefore it is impossible for any accidental dispositions
to pre-exist in matter before the substantial form, and consequently
before the soul.
Reply to Objection 1: As appears from what has been already said (Article ), the more
perfect form virtually contains whatever belongs to the inferior forms;
therefore while remaining one and the same, it perfects matter according
to the various degrees of perfection. For the same essential form makes
man an actual being, a body, a living being, an animal, and a man. Now it
is clear that to every "genus" follow its own proper accidents. Therefore
as matter is apprehended as perfected in its existence, before it is
understood as corporeal, and so on; so those accidents which belong to
existence are understood to exist before corporeity; and thus
dispositions are understood in matter before the form, not as regards all
its effects, but as regards the subsequent effect.
Reply to Objection 2: Dimensions of quantity are accidents consequent to the
corporeity which belongs to the whole matter. Wherefore matter, once
understood as corporeal and measurable, can be understood as distinct in
its various parts, and as receptive of different forms according to the
further degrees of perfection. For although it is essentially the same
form which gives matter the various degrees of perfection, as we have
said (ad 1), yet it is considered as different when brought under the
observation of reason.
Reply to Objection 3: A spiritual substance which is united to a body as its
motor only, is united thereto by power or virtue. But the intellectual
soul is united by its very being to the body as a form; and yet it guides
and moves the body by its power and virtue.
Article 7: Whether the soul is united to the animal body by means of a body?
Objection 1: It seems that the soul is united to the animal body by means of a
body. For Augustine says (Gen. ad lit. vii, 19), that "the soul
administers the body by light," that is, by fire, "and by air, which is
most akin to a spirit." But fire and air are bodies. Therefore the soul
is united to the human body by means of a body.
Objection 2: Further, a link between two things seems to be that thing the
removal of which involves the cessation of their union. But when
breathing ceases, the soul is separated from the body. Therefore the
breath, which is a subtle body, is the means of union between soul and
Objection 3: Further, things which are very distant from one another, are not
united except by something between them. But the intellectual soul is
very distant from the body, both because it is incorporeal, and because
it is incorruptible. Therefore it seems to be united to the body by means
of an incorruptible body, and such would be some heavenly light, which
would harmonize the elements, and unite them together.
On the contrary, The Philosopher says (De Anima ii, 1): "We need not ask
if the soul and body are one, as neither do we ask if wax and its shape
are one." But the shape is united to the wax without a body intervening.
Therefore also the soul is thus united to the body.
I answer that, If the soul, according to the Platonists, were united to
the body merely as a motor, it would be right to say that some other
bodies must intervene between the soul and body of man, or any animal
whatever; for a motor naturally moves what is distant from it by means of
If, however, the soul is united to the body as its form, as we have said
(Article ), it is impossible for it to be united by means of another body.
The reason of this is that a thing is one, according as it is a being.
Now the form, through itself, makes a thing to be actual since it is
itself essentially an act; nor does it give existence by means of
something else. Wherefore the unity of a thing composed of matter and
form, is by virtue of the form itself, which by reason of its very nature
is united to matter as its act. Nor is there any other cause of union
except the agent, which causes matter to be in act, as the Philosopher
says, Metaph. viii (Did. vii, 6).
From this it is clear how false are the opinions of those who maintained
the existence of some mediate bodies between the soul and body of man. Of
these certain Platonists said that the intellectual soul has an
incorruptible body naturally united to it, from which it is never
separated, and by means of which it is united to the corruptible body of
man. Others said that the soul is united to the body by means of a
corporeal spirit. Others said it is united to the body by means of light,
which, they say, is a body and of the nature of the fifth essence; so
that the vegetative soul would be united to the body by means of the
light of the sidereal heaven; the sensible soul, by means of the light of
the crystal heaven; and the intellectual soul by means of the light of
the empyrean heaven. Now all this is fictious and ridiculous: for light
is not a body; and the fifth essence does not enter materially into the
composition of a mixed body (since it is unchangeable), but only
virtually: and lastly, because the soul is immediately united to the body
as the form to matter.
Reply to Objection 1: Augustine speaks there of the soul as it moves the body;
whence he uses the word "administration." It is true that it moves the
grosser parts of the body by the more subtle parts. And the first
instrument of the motive power is a kind of spirit, as the Philosopher
says in De causa motus animalium (De mot. animal. x).
Reply to Objection 2: The union of soul and body ceases at the cessation of
breath, not because this is the means of union, but because of the
removal of that disposition by which the body is disposed for such a
union. Nevertheless the breath is a means of moving, as the first
instrument of motion.
Reply to Objection 3: The soul is indeed very distant from the body, if we
consider the condition of each separately: so that if each had a separate
existence, many means of connection would have to intervene. But inasmuch
as the soul is the form of the body, it has not an existence apart from
the existence of the body, but by its own existence is united to the body
immediately. This is the case with every form which, if considered as an
act, is very distant from matter, which is a being only in potentiality.
Article 8: Whether the soul is in each part of the body?
Objection 1: It would seem that the whole soul is not in each part of the
body; for the Philosopher says in De causa motus animalium (De mot.
animal. x): "It is not necessary for the soul to be in each part of the
body; it suffices that it be in some principle of the body causing the
other parts to live, for each part has a natural movement of its own."
Objection 2: Further, the soul is in the body of which it is the act. But it
is the act of an organic body. Therefore it exists only in an organic
body. But each part of the human body is not an organic body. Therefore
the whole soul is not in each part.
Objection 3: Further, the Philosopher says (De Anima. ii, 1) that the relation
of a part of the soul to a part of the body, such as the sight to the
pupil of the eye, is the same as the relation of the soul to the whole
body of an animal. If, therefore, the whole soul is in each part of the
body, it follows that each part of the body is an animal.
Objection 4: Further, all the powers of the soul are rooted in the essence of
the soul. If, therefore, the whole soul be in each part of the body, it
follows that all the powers of the soul are in each part of the body;
thus the sight will be in the ear, and hearing in the eye, and this is
Objection 5: Further, if the whole soul is in each part of the body, each part
of the body is immediately dependent on the soul. Thus one part would not
depend on another; nor would one part be nobler than another; which is
clearly untrue. Therefore the soul is not in each part of the body.
On the contrary, Augustine says (De Trin. vi, 6), that "in each body the
whole soul is in the whole body, and in each part is entire."
I answer that, As we have said, if the soul were united to the body
merely as its motor, we might say that it is not in each part of the
body, but only in one part through which it would move the others. But
since the soul is united to the body as its form, it must necessarily be
in the whole body, and in each part thereof. For it is not an accidental
form, but the substantial form of the body. Now the substantial form
perfects not only the whole, but each part of the whole. For since a
whole consists of parts, a form of the whole which does not give
existence to each of the parts of the body, is a form consisting in
composition and order, such as the form of a house; and such a form is
accidental. But the soul is a substantial form; and therefore it must be
the form and the act, not only of the whole, but also of each part.
Therefore, on the withdrawal of the soul, as we do not speak of an
animal or a man unless equivocally, as we speak of a painted animal or a
stone animal; so is it with the hand, the eye, the flesh and bones, as
the Philosopher says (De Anima ii, 1). A proof of which is, that on the
withdrawal of the soul, no part of the body retains its proper action;
although that which retains its species, retains the action of the
species. But act is in that which it actuates: wherefore the soul must be
in the whole body, and in each part thereof.
That it is entire in each part thereof, may be concluded from this, that
since a whole is that which is divided into parts, there are three kinds
of totality, corresponding to three kinds of division. There is a whole
which is divided into parts of quantity, as a whole line, or a whole
body. There is also a whole which is divided into logical and essential
parts: as a thing defined is divided into the parts of a definition, and
a composite into matter and form. There is, further, a third kind of
whole which is potential, divided into virtual parts. The first kind of
totality does not apply to forms, except perhaps accidentally; and then
only to those forms, which have an indifferent relationship to a
quantitative whole and its parts; as whiteness, as far as its essence is
concerned, is equally disposed to be in the whole surface and in each
part of the surface; and, therefore, the surface being divided, the
whiteness is accidentally divided. But a form which requires variety in
the parts, such as a soul, and specially the soul of perfect animals, is
not equally related to the whole and the parts: hence it is not divided
accidentally when the whole is divided. So therefore quantitative
totality cannot be attributed to the soul, either essentially or
accidentally. But the second kind of totality, which depends on logical
and essential perfection, properly and essentially belongs to forms: and
likewise the virtual totality, because a form is the principle of
Therefore if it be asked whether the whole whiteness is in the whole
surface and in each part thereof, it is necessary to distinguish. If we
mean quantitative totality which whiteness has accidentally, then the
whole whiteness is not in each part of the surface. The same is to be
said of totality of power: since the whiteness which is in the whole
surface moves the sight more than the whiteness which is in a small part
thereof. But if we mean totality of species and essence, then the whole
whiteness is in each part of a surface.
Since, however, the soul has not quantitative totality, neither
essentially, nor accidentally, as we have seen; it is enough to say that
the whole soul is in each part of the body, by totality of perfection and
of essence, but not by totality of power. For it is not in each part of
the body, with regard to each of its powers; but with regard to sight, it
is in the eye; and with regard to hearing, it is in the ear; and so
forth. We must observe, however, that since the soul requires variety of
parts, its relation to the whole is not the same as its relation to the
parts; for to the whole it is compared primarily and essentially, as to
its proper and proportionate perfectible; but to the parts, secondarily,
inasmuch as they are ordained to the whole.
Reply to Objection 1: The Philosopher is speaking there of the motive power of
Reply to Objection 2: The soul is the act of an organic body, as of its primary
and proportionate perfectible.
Reply to Objection 3: An animal is that which is composed of a soul and a whole
body, which is the soul's primary and proportionate perfectible. Thus the
soul is not in a part. Whence it does not follow that a part of an animal
is an animal.
Reply to Objection 4: Some of the powers of the soul are in it according as it
exceeds the entire capacity of the body, namely the intellect and the
will; whence these powers are not said to be in any part of the body.
Other powers are common to the soul and body; wherefore each of these
powers need not be wherever the soul is, but only in that part of the
body, which is adapted to the operation of such a power.
Reply to Objection 5: One part of the body is said to be nobler than another, on
account of the various powers, of which the parts of the body are the
organs. For that part which is the organ of a nobler power, is a nobler
part of the body: as also is that part which serves the same power in a