QUESTION 84: HOW THE SOUL WHILE UNITED TO THE BODY UNDERSTANDS CORPOREAL THINGS BENEATH IT
We now have to consider the acts of the soul in regard to the
intellectual and the appetitive powers: for the other powers of the soul
do not come directly under the consideration of the theologian.
Furthermore, the acts of the appetitive part of the soul come under the
consideration of the science of morals; wherefore we shall treat of them
in the second part of this work, to which the consideration of moral
matters belongs. But of the acts of the intellectual part we shall treat
In treating of these acts we shall proceed in the following order:
First, we shall inquire how the soul understands when united to the body;
secondly, how it understands when separated therefrom.
The former of these inquiries will be threefold: (1) How the soul
understands bodies which are beneath it; (2) How it understands itself
and things contained in itself; (3) How it understands immaterial
substances, which are above it.
In treating of the knowledge of corporeal things there are three points
to be considered: (1) Through what does the soul know them? (2) How and
in what order does it know them? (3) What does it know in them?
Under the first head there are eight points of inquiry:
(1) Whether the soul knows bodies through the intellect?
(2) Whether it understands them through its essence, or through any
(3) If through some species, whether the species of all things
intelligible are naturally innate in the soul?
(4) Whether these species are derived by the soul from certain separate
(5) Whether our soul sees in the eternal ideas all that it understands?
(6) Whether it acquires intellectual knowledge from the senses?
(7) Whether the intellect can, through the species of which it is
possessed, actually understand, without turning to the phantasms?
(8) Whether the judgment of the intellect is hindered by an obstacle in
the sensitive powers?
Article 1: Whether the soul knows bodies through the intellect?
Objection 1: It would seem that the soul does not know bodies through the
intellect. For Augustine says (Soliloq. ii, 4) that "bodies cannot be
understood by the intellect; nor indeed anything corporeal unless it can
be perceived by the senses." He says also (Gen. ad lit. xii, 24) that
intellectual vision is of those things that are in the soul by their
essence. But such are not bodies. Therefore the soul cannot know bodies
through the intellect.
Objection 2: Further, as sense is to the intelligible, so is the intellect to
the sensible. But the soul can by no means, through the senses,
understand spiritual things, which are intelligible. Therefore by no
means can it, through the intellect, know bodies, which are sensible.
Objection 3: Further, the intellect is concerned with things that are
necessary and unchangeable. But all bodies are mobile and changeable.
Therefore the soul cannot know bodies through the intellect.
On the contrary, Science is in the intellect. If, therefore, the
intellect does not know bodies, it follows that there is no science of
bodies; and thus perishes natural science, which treats of mobile bodies.
I answer that, It should be said in order to elucidate this question,
that the early philosophers, who inquired into the natures of things,
thought there was nothing in the world save bodies. And because they
observed that all bodies are mobile, and considered them to be ever in a
state of flux, they were of opinion that we can have no certain knowledge
of the true nature of things. For what is in a continual state of flux,
cannot be grasped with any degree of certitude, for it passes away ere
the mind can form a judgment thereon: according to the saying of
Heraclitus, that "it is not possible twice to touch a drop of water in a
passing torrent," as the Philosopher relates (Metaph. iv, Did. iii, 5).
After these came Plato, who, wishing to save the certitude of our
knowledge of truth through the intellect, maintained that, besides these
things corporeal, there is another genus of beings, separate from matter
and movement, which beings he called "species" or "ideas," by
participation of which each one of these singular and sensible things is
said to be either a man, or a horse, or the like. Wherefore he said that
sciences and definitions, and whatever appertains to the act of the
intellect, are not referred to these sensible bodies, but to those beings
immaterial and separate: so that according to this the soul does not
understand these corporeal things, but the separate species thereof.
Now this may be shown to be false for two reasons. First, because, since
those species are immaterial and immovable, knowledge of movement and
matter would be excluded from science (which knowledge is proper to
natural science), and likewise all demonstration through moving and
material causes. Secondly, because it seems ridiculous, when we seek for
knowledge of things which are to us manifest, to introduce other beings,
which cannot be the substance of those others, since they differ from
them essentially: so that granted that we have a knowledge of those
separate substances, we cannot for that reason claim to form a judgment
concerning these sensible things.
Now it seems that Plato strayed from the truth because, having observed
that all knowledge takes place through some kind of similitude, he
thought that the form of the thing known must of necessity be in the
knower in the same manner as in the thing known. Then he observed that
the form of the thing understood is in the intellect under conditions of
universality, immateriality, and immobility: which is apparent from the
very operation of the intellect, whose act of understanding has a
universal extension, and is subject to a certain amount of necessity: for
the mode of action corresponds to the mode of the agent's form. Wherefore
he concluded that the things which we understand must have in themselves
an existence under the same conditions of immateriality and immobility.
But there is no necessity for this. For even in sensible things it is to
be observed that the form is otherwise in one sensible than in another:
for instance, whiteness may be of great intensity in one, and of a less
intensity in another: in one we find whiteness with sweetness, in another
without sweetness. In the same way the sensible form is conditioned
differently in the thing which is external to the soul, and in the senses
which receive the forms of sensible things without receiving matter, such
as the color of gold without receiving gold. So also the intellect,
according to its own mode, receives under conditions of immateriality and
immobility, the species of material and mobile bodies: for the received
is in the receiver according to the mode of the receiver. We must
conclude, therefore, that through the intellect the soul knows bodies by
a knowledge which is immaterial, universal, and necessary.
Reply to Objection 1: These words of Augustine are to be understood as referring
to the medium of intellectual knowledge, and not to its object. For the
intellect knows bodies by understanding them, not indeed through bodies,
nor through material and corporeal species; but through immaterial and
intelligible species, which can be in the soul by their own essence.
Reply to Objection 2: As Augustine says (De Civ. Dei xxii, 29), it is not correct
to say that as the sense knows only bodies so the intellect knows only
spiritual things; for it follows that God and the angels would not know
corporeal things. The reason of this diversity is that the lower power
does not extend to those things that belong to the higher power; whereas
the higher power operates in a more excellent manner those things which
belong to the lower power.
Reply to Objection 3: Every movement presupposes something immovable: for when a
change of quality occurs, the substance remains unmoved; and when there
is a change of substantial form, matter remains unmoved. Moreover the
various conditions of mutable things are themselves immovable; for
instance, though Socrates be not always sitting, yet it is an immovable
truth that whenever he does sit he remains in one place. For this reason
there is nothing to hinder our having an immovable science of movable
Article 2: Whether the soul understands corporeal things through its essence?
Objection 1: It would seem that the soul understands corporeal things through
its essence. For Augustine says (De Trin. x, 5) that the soul "collects
and lays hold of the images of bodies which are formed in the soul and of
the soul: for in forming them it gives them something of its own
substance." But the soul understands bodies by images of bodies.
Therefore the soul knows bodies through its essence, which it employs for
the formation of such images, and from which it forms them.
Objection 2: Further, the Philosopher says (De Anima iii, 8) that "the soul,
after a fashion, is everything." Since, therefore, like is known by like,
it seems that the soul knows corporeal things through itself.
Objection 3: Further, the soul is superior to corporeal creatures. Now lower
things are in higher things in a more eminent way than in themselves, as
Dionysius says (Coel. Hier. xii). Therefore all corporeal creatures exist
in a more excellent way in the soul than in themselves. Therefore the
soul can know corporeal creatures through its essence.
On the contrary, Augustine says (De Trin. ix, 3) that "the mind gathers
knowledge of corporeal things through the bodily senses." But the soul
itself cannot be known through the bodily senses. Therefore it does not
know corporeal things through itself.
I answer that, The ancient philosophers held that the soul knows bodies
through its essence. For it was universally admitted that "like is known
by like." But they thought that the form of the thing known is in the
knower in the same mode as in the thing known. The Platonists however
were of a contrary opinion. For Plato, having observed that the
intellectual soul has an immaterial nature, and an immaterial mode of
knowledge, held that the forms of things known subsist immaterially.
While the earlier natural philosophers, observing that things known are
corporeal and material, held that things known must exist materially even
in the soul that knows them. And therefore, in order to ascribe to the
soul a knowledge of all things, they held that it has the same nature in
common with all. And because the nature of a result is determined by its
principles, they ascribed to the soul the nature of a principle; so that
those who thought fire to be the principle of all, held that the soul had
the nature of fire; and in like manner as to air and water. Lastly,
Empedocles, who held the existence of our four material elements and two
principles of movement, said that the soul was composed of these.
Consequently, since they held that things exist in the soul materially,
they maintained that all the soul's knowledge is material, thus failing
to discern intellect from sense.
But this opinion will not hold. First, because in the material principle
of which they spoke, the various results do not exist save in
potentiality. But a thing is not known according as it is in
potentiality, but only according as it is in act, as is shown Metaph. ix
(Did. viii, 9): wherefore neither is a power known except through its
act. It is therefore insufficient to ascribe to the soul the nature of
the principles in order to explain the fact that it knows all, unless we
further admit in the soul natures and forms of each individual result,
for instance, of bone, flesh, and the like; thus does Aristotle argue
against Empedocles (De Anima i, 5). Secondly, because if it were
necessary for the thing known to exist materially in the knower, there
would be no reason why things which have a material existence outside the
soul should be devoid of knowledge; why, for instance, if by fire the
soul knows fire, that fire also which is outside the soul should not have
knowledge of fire.
We must conclude, therefore, that material things known must needs exist
in the knower, not materially, but immaterially. The reason of this is,
because the act of knowledge extends to things outside the knower: for we
know things even that are external to us. Now by matter the form of a
thing is determined to some one thing. Wherefore it is clear that
knowledge is in inverse ratio of materiality. And consequently things
that are not receptive of forms save materially, have no power of
knowledge whatever---such as plants, as the Philosopher says (De Anima
ii, 12). But the more immaterially a thing receives the form of the thing
known, the more perfect is its knowledge. Therefore the intellect which
abstracts the species not only from matter, but also from the
individuating conditions of matter, has more perfect knowledge than the
senses, which receive the form of the thing known, without matter indeed,
but subject to material conditions. Moreover, among the senses, sight has
the most perfect knowledge, because it is the least material, as we have
remarked above (Question , Article ): while among intellects the more perfect is
the more immaterial.
It is therefore clear from the foregoing, that if there be an intellect
which knows all things by its essence, then its essence must needs have
all things in itself immaterially; thus the early philosophers held that
the essence of the soul, that it may know all things, must be actually
composed of the principles of all material things. Now this is proper to
God, that His Essence comprise all things immaterially as effects
pre-exist virtually in their cause. God alone, therefore, understands all
things through His Essence: but neither the human soul nor the angels can
Reply to Objection 1: Augustine in that passage is speaking of an imaginary
vision, which takes place through the image of bodies. To the formation
of such images the soul gives part of its substance, just as a subject is
given in order to be informed by some form. In this way the soul makes
such images from itself; not that the soul or some part of the soul be
turned into this or that image; but just as we say that a body is made
into something colored because of its being informed with color. That
this is the sense, is clear from what follows. For he says that the soul
"keeps something"---namely, not informed with such image---"which is able
freely to judge of the species of these images": and that this is the
"mind" or "intellect." And he says that the part which is informed with
these images---namely, the imagination---is "common to us and beasts."
Reply to Objection 2: Aristotle did not hold that the soul is actually composed
of all things, as did the earlier philosophers; he said that the soul is
all things, "after a fashion," forasmuch as it is in potentiality to
all---through the senses, to all things sensible---through the intellect,
to all things intelligible.
Reply to Objection 3: Every creature has a finite and determinate essence.
Wherefore although the essence of the higher creature has a certain
likeness to the lower creature, forasmuch as they have something in
common generically, yet it has not a complete likeness thereof, because
it is determined to a certain species other than the species of the lower
creature. But the Divine Essence is a perfect likeness of all, whatsoever
may be found to exist in things created, being the universal principle of
Article 3: Whether the soul understands all things through innate species?
Objection 1: It would seem that the soul understands all things through innate
species. For Gregory says, in a homily for the Ascension (xxix in Ev.),
that "man has understanding in common with the angels." But angels
understand all things through innate species: wherefore in the book De
Causis it is said that "every intelligence is full of forms." Therefore
the soul also has innate species of things, by means of which it
understands corporeal things.
Objection 2: Further, the intellectual soul is more excellent than corporeal
primary matter. But primary matter was created by God under the forms to
which it has potentiality. Therefore much more is the intellectual soul
created by God under intelligible species. And so the soul understands
corporeal things through innate species.
Objection 3: Further, no one can answer the truth except concerning what he
knows. But even a person untaught and devoid of acquired knowledge,
answers the truth to every question if put to him in orderly fashion, as
we find related in the Meno (xv seqq.) of Plato, concerning a certain
individual. Therefore we have some knowledge of things even before we
acquire knowledge; which would not be the case unless we had innate
species. Therefore the soul understands corporeal things through innate
On the contrary, The Philosopher, speaking of the intellect, says (De
Anima iii, 4) that it is like "a tablet on which nothing is written."
I answer that, Since form is the principle of action, a thing must be
related to the form which is the principle of an action, as it is to that
action: for instance, if upward motion is from lightness, then that
which only potentially moves upwards must needs be only potentially
light, but that which actually moves upwards must needs be actually
light. Now we observe that man sometimes is only a potential knower, both
as to sense and as to intellect. And he is reduced from such potentiality
to act---through the action of sensible objects on his senses, to the act
of sensation---by instruction or discovery, to the act of understanding.
Wherefore we must say that the cognitive soul is in potentiality both to
the images which are the principles of sensing, and to those which are
the principles of understanding. For this reason Aristotle (De Anima iii,
4) held that the intellect by which the soul understands has no innate
species, but is at first in potentiality to all such species.
But since that which has a form actually, is sometimes unable to act
according to that form on account of some hindrance, as a light thing may
be hindered from moving upwards; for this reason did Plato hold that
naturally man's intellect is filled with all intelligible species, but
that, by being united to the body, it is hindered from the realization of
its act. But this seems to be unreasonable. First, because, if the soul
has a natural knowledge of all things, it seems impossible for the soul
so far to forget the existence of such knowledge as not to know itself to
be possessed thereof: for no man forgets what he knows naturally; that,
for instance, the whole is larger than the part, and such like. And
especially unreasonable does this seem if we suppose that it is natural
to the soul to be united to the body, as we have established above (Question , Article ): for it is unreasonable that the natural operation of a thing be
totally hindered by that which belongs to it naturally. Secondly, the
falseness of this opinion is clearly proved from the fact that if a sense
be wanting, the knowledge of what is apprehended through that sense is
wanting also: for instance, a man who is born blind can have no knowledge
of colors. This would not be the case if the soul had innate images of
all intelligible things. We must therefore conclude that the soul does
not know corporeal things through innate species.
Reply to Objection 1: Man indeed has intelligence in common with the angels, but
not in the same degree of perfection: just as the lower grades of bodies,
which merely exist, according to Gregory (Homily on Ascension, xxix In
Ev.), have not the same degree of perfection as the higher bodies. For
the matter of the lower bodies is not totally completed by its form, but
is in potentiality to forms which it has not: whereas the matter of
heavenly bodies is totally completed by its form, so that it is not in
potentiality to any other form, as we have said above (Question , Article ). In
the same way the angelic intellect is perfected by intelligible species,
in accordance with its nature; whereas the human intellect is in
potentiality to such species.
Reply to Objection 2: Primary matter has substantial being through its form,
consequently it had need to be created under some form: else it would not
be in act. But when once it exists under one form it is in potentiality
to others. On the other hand, the intellect does not receive substantial
being through the intelligible species; and therefore there is no
Reply to Objection 3: If questions be put in an orderly fashion they proceed from
universal self-evident principles to what is particular. Now by such a
process knowledge is produced in the mind of the learner. Wherefore when
he answers the truth to a subsequent question, this is not because he had
knowledge previously, but because he thus learns for the first time. For
it matters not whether the teacher proceed from universal principles to
conclusions by questioning or by asserting; for in either case the mind
of the listener is assured of what follows by that which preceded.
Article 4: Whether the intelligible species are derived by the soul from certain separate forms?
Objection 1: It would seem that the intelligible species are derived by the
soul from some separate forms. For whatever is such by participation is
caused by what is such essentially; for instance, that which is on fire
is reduced to fire as the cause thereof. But the intellectual soul
forasmuch as it is actually understanding, participates the thing
understood: for, in a way, the intellect in act is the thing understood
in act. Therefore what in itself and in its essence is understood in act,
is the cause that the intellectual soul actually understands. Now that
which in its essence is actually understood is a form existing without
matter. Therefore the intelligible species, by which the soul
understands, are caused by some separate forms.
Objection 2: Further, the intelligible is to the intellect, as the sensible is
to the sense. But the sensible species which are in the senses, and by
which we sense, are caused by the sensible object which exists actually
outside the soul. Therefore the intelligible species, by which our
intellect understands, are caused by some things actually intelligible,
existing outside the soul. But these can be nothing else than forms
separate from matter. Therefore the intelligible forms of our intellect
are derived from some separate substances.
Objection 3: Further, whatever is in potentiality is reduced to act by
something actual. If, therefore, our intellect, previously in
potentiality, afterwards actually understands, this must needs be caused
by some intellect which is always in act. But this is a separate
intellect. Therefore the intelligible species, by which we actually
understand, are caused by some separate substances.
On the contrary, If this were true we should not need the senses in
order to understand. And this is proved to be false especially from the
fact that if a man be wanting in a sense, he cannot have any knowledge of
the sensibles corresponding to that sense.
I answer that, Some have held that the intelligible species of our
intellect are derived from certain separate forms or substances. And this
in two ways. For Plato, as we have said (Article ), held that the forms of
sensible things subsist by themselves without matter; for instance, the
form of a man which he called "per se" man, and the form or idea of a
horse which is called "per se" horse, and so forth. He said therefore
that these forms are participated both by our soul and by corporeal
matter; by our soul, to the effect of knowledge thereof, and by corporeal
matter to the effect of existence: so that, just as corporeal matter by
participating the idea of a stone, becomes an individuating stone, so our
intellect, by participating the idea of a stone, is made to understand a
stone. Now participation of an idea takes place by some image of the idea
in the participator, just as a model is participated by a copy. So just
as he held that the sensible forms, which are in corporeal matter, are
derived from the ideas as certain images thereof: so he held that the
intelligible species of our intellect are images of the ideas, derived
therefrom. And for this reason, as we have said above (Article ), he referred
sciences and definitions to those ideas.
But since it is contrary to the nature of sensible things that their
forms should subsist without matter, as Aristotle proves in many ways
(Metaph. vi), Avicenna (De Anima v) setting this opinion aside, held that
the intelligible species of all sensible things, instead of subsisting in
themselves without matter, pre-exist immaterially in the separate
intellects: from the first of which, said he, such species are derived by
a second, and so on to the last separate intellect which he called the
"active intelligence," from which, according to him, intelligible species
flow into our souls, and sensible species into corporeal matter. And so
Avicenna agrees with Plato in this, that the intelligible species of our
intellect are derived from certain separate forms; but these Plato held
to subsist of themselves, while Avicenna placed them in the "active
intelligence." They differ, too, in this respect, that Avicenna held that
the intelligible species do not remain in our intellect after it has
ceased actually to understand, and that it needs to turn (to the active
intellect) in order to receive them anew. Consequently he does not hold
that the soul has innate knowledge, as Plato, who held that the
participated ideas remain immovably in the soul.
But in this opinion no sufficient reason can be assigned for the soul
being united to the body. For it cannot be said that the intellectual
soul is united to the body for the sake of the body: for neither is form
for the sake of matter, nor is the mover for the sake of the moved, but
rather the reverse. Especially does the body seem necessary to the
intellectual soul, for the latter's proper operation which is to
understand: since as to its being the soul does not depend on the body.
But if the soul by its very nature had an inborn aptitude for receiving
intelligible species through the influence of only certain separate
principles, and were not to receive them from the senses, it would not
need the body in order to understand: wherefore to no purpose would it be
united to the body.
But if it be said that our soul needs the senses in order to understand,
through being in some way awakened by them to the consideration of those
things, the intelligible species of which it receives from the separate
principles: even this seems an insufficient explanation. For this
awakening does not seem necessary to the soul, except in as far as it is
overcome by sluggishness, as the Platonists expressed it, and by
forgetfulness, through its union with the body: and thus the senses would
be of no use to the intellectual soul except for the purpose of removing
the obstacle which the soul encounters through its union with the body.
Consequently the reason of the union of the soul with the body still
remains to be sought.
And if it be said with Avicenna, that the senses are necessary to the
soul, because by them it is aroused to turn to the "active intelligence"
from which it receives the species: neither is this a sufficient
explanation. Because if it is natural for the soul to understand through
species derived from the "active intelligence," it follows that at times
the soul of an individual wanting in one of the senses can turn to the
active intelligence, either from the inclination of its very nature, or
through being roused by another sense, to the effect of receiving the
intelligible species of which the corresponding sensible species are
wanting. And thus a man born blind could have knowledge of colors; which
is clearly untrue. We must therefore conclude that the intelligible
species, by which our soul understands, are not derived from separate
Reply to Objection 1: The intelligible species which are participated by our
intellect are reduced, as to their first cause, to a first principle
which is by its essence intelligible---namely, God. But they proceed from
that principle by means of the sensible forms and material things, from
which we gather knowledge, as Dionysius says (Div. Nom. vii).
Reply to Objection 2: Material things, as to the being which they have outside
the soul, may be actually sensible, but not actually intelligible.
Wherefore there is no comparison between sense and intellect.
Reply to Objection 3: Our passive intellect is reduced from potentiality to act
by some being in act, that is, by the active intellect, which is a power
of the soul, as we have said (Question , Article ); and not by a separate
intelligence, as proximate cause, although perchance as remote cause.
Article 5: Whether the intellectual soul knows material things in the eternal types?
Objection 1: It would seem that the intellectual soul does not know material
things in the eternal types. For that in which anything is known must
itself be known more and previously. But the intellectual soul of man,
in the present state of life, does not know the eternal types: for it
does not know God in Whom the eternal types exist, but is "united to God
as to the unknown," as Dionysius says (Myst. Theolog. i). Therefore the
soul does not know all in the eternal types.
Objection 2: Further, it is written (Rm. 1:20) that "the invisible things of
God are clearly seen . . . by the things that are made." But among the
invisible things of God are the eternal types. Therefore the eternal
types are known through creatures and not the converse.
Objection 3: Further, the eternal types are nothing else but ideas, for
Augustine says (Questions. 83, qu. 46) that "ideas are permanent types existing
in the Divine mind." If therefore we say that the intellectual soul knows
all things in the eternal types, we come back to the opinion of Plato who
said that all knowledge is derived from them.
On the contrary, Augustine says (Confess. xii, 25): "If we both see that
what you say is true, and if we both see that what I say is true, where
do we see this, I pray? Neither do I see it in you, nor do you see it in
me: but we both see it in the unchangeable truth which is above our
minds." Now the unchangeable truth is contained in the eternal types.
Therefore the intellectual soul knows all true things in the eternal
I answer that, As Augustine says (De Doctr. Christ. ii, 11): "If those
who are called philosophers said by chance anything that was true and
consistent with our faith, we must claim it from them as from unjust
possessors. For some of the doctrines of the heathens are spurious
imitations or superstitious inventions, which we must be careful to avoid
when we renounce the society of the heathens." Consequently whenever
Augustine, who was imbued with the doctrines of the Platonists, found in
their teaching anything consistent with faith, he adopted it: and those
thing which he found contrary to faith he amended. Now Plato held, as we
have said above (Article ), that the forms of things subsist of themselves
apart from matter; and these he called ideas, by participation of which
he said that our intellect knows all things: so that just as corporeal
matter by participating the idea of a stone becomes a stone, so our
intellect, by participating the same idea, has knowledge of a stone. But
since it seems contrary to faith that forms of things themselves, outside
the things themselves and apart from matter, as the Platonists held,
asserting that "per se" life or "per se" wisdom are creative substances,
as Dionysius relates (Div. Nom. xi); therefore Augustine (Questions. 83, qu.
46), for the ideas defended by Plato, substituted the types of all
creatures existing in the Divine mind, according to which types all
things are made in themselves, and are known to the human soul.
When, therefore, the question is asked: Does the human soul know all
things in the eternal types? we must reply that one thing is said to be
known in another in two ways. First, as in an object itself known; as
one may see in a mirror the images of things reflected therein. In this
way the soul, in the present state of life, cannot see all things in the
eternal types; but the blessed who see God, and all things in Him, thus
know all things in the eternal types. Secondly, on thing is said to be
known in another as in a principle of knowledge: thus we might say that
we see in the sun what we see by the sun. And thus we must needs say that
the human soul knows all things in the eternal types, since by
participation of these types we know all things. For the intellectual
light itself which is in us, is nothing else than a participated likeness
of the uncreated light, in which are contained the eternal types. Whence
it is written (Ps. 4:6,7), "Many say: Who showeth us good things?" which
question the Psalmist answers, "The light of Thy countenance, O Lord, is
signed upon us," as though he were to say: By the seal of the Divine
light in us, all things are made known to us.
But since besides the intellectual light which is in us, intelligible
species, which are derived from things, are required in order for us to
have knowledge of material things; therefore this same knowledge is not
due merely to a participation of the eternal types, as the Platonists
held, maintaining that the mere participation of ideas sufficed for
knowledge. Wherefore Augustine says (De Trin. iv, 16): "Although the
philosophers prove by convincing arguments that all things occur in time
according to the eternal types, were they able to see in the eternal
types, or to find out from them how many kinds of animals there are and
the origin of each? Did they not seek for this information from the story
of times and places?"
But that Augustine did not understand all things to be known in their
"eternal types" or in the "unchangeable truth," as though the eternal
types themselves were seen, is clear from what he says (Questions. 83, qu.
46)---viz. that "not each and every rational soul can be said to be
worthy of that vision," namely, of the eternal types, "but only those
that are holy and pure," such as the souls of the blessed.
From what has been said the objections are easily solved.
Article 6: Whether intellectual knowledge is derived from sensible things?
Objection 1: It would seem that intellectual knowledge is not derived from
sensible things. For Augustine says (Questions. 83, qu. 9) that "we cannot
expect to learn the fulness of truth from the senses of the body." This
he proves in two ways. First, because "whatever the bodily senses reach,
is continually being changed; and what is never the same cannot be
perceived." Secondly, because, "whatever we perceive by the body, even
when not present to the senses, may be present to the imagination, as
when we are asleep or angry: yet we cannot discern by the senses, whether
what we perceive be the sensible object or the deceptive image thereof.
Now nothing can be perceived which cannot be distinguished from its
counterfeit." And so he concludes that we cannot expect to learn the
truth from the senses. But intellectual knowledge apprehends the truth.
Therefore intellectual knowledge cannot be conveyed by the senses.
Objection 2: Further, Augustine says (Gen. ad lit. xii, 16): "We must not
thing that the body can make any impression on the spirit, as though the
spirit were to supply the place of matter in regard to the body's action;
for that which acts is in every way more excellent than that which it
acts on." Whence he concludes that "the body does not cause its image in
the spirit, but the spirit causes it in itself." Therefore intellectual
knowledge is not derived from sensible things.
Objection 3: Further, an effect does not surpass the power of its cause. But
intellectual knowledge extends beyond sensible things: for we understand
some things which cannot be perceived by the senses. Therefore
intellectual knowledge is not derived from sensible things.
On the contrary, The Philosopher says (Metaph. i, 1; Poster. ii, 15)
that the principle of knowledge is in the senses.
I answer that, On this point the philosophers held three opinions. For
Democritus held that "all knowledge is caused by images issuing from the
bodies we think of and entering into our souls," as Augustine says in his
letter to Dioscorus (cxviii, 4). And Aristotle says (De Somn. et Vigil.)
that Democritus held that knowledge is cause by a "discharge of images."
And the reason for this opinion was that both Democritus and the other
early philosophers did not distinguish between intellect and sense, as
Aristotle relates (De Anima iii, 3). Consequently, since the sense is
affected by the sensible, they thought that all our knowledge is affected
by this mere impression brought about by sensible things. Which
impression Democritus held to be caused by a discharge of images.
Plato, on the other hand, held that the intellect is distinct from the
senses: and that it is an immaterial power not making use of a corporeal
organ for its action. And since the incorporeal cannot be affected by the
corporeal, he held that intellectual knowledge is not brought about by
sensible things affecting the intellect, but by separate intelligible
forms being participated by the intellect, as we have said above (Articles ,5). Moreover he held that sense is a power operating of itself.
Consequently neither is sense, since it is a spiritual power, affected by
the sensible: but the sensible organs are affected by the sensible, the
result being that the soul is in a way roused to form within itself the
species of the sensible. Augustine seems to touch on this opinion (Gen.
ad lit. xii, 24) where he says that the "body feels not, but the soul
through the body, which it makes use of as a kind of messenger, for
reproducing within itself what is announced from without." Thus according
to Plato, neither does intellectual knowledge proceed from sensible
knowledge, nor sensible knowledge exclusively from sensible things; but
these rouse the sensible soul to the sentient act, while the senses rouse
the intellect to the act of understanding.
Aristotle chose a middle course. For with Plato he agreed that intellect
and sense are different. But he held that the sense has not its proper
operation without the cooperation of the body; so that to feel is not an
act of the soul alone, but of the "composite." And he held the same in
regard to all the operations of the sensitive part. Since, therefore, it
is not unreasonable that the sensible objects which are outside the soul
should produce some effect in the "composite," Aristotle agreed with
Democritus in this, that the operations of the sensitive part are caused
by the impression of the sensible on the sense: not by a discharge, as
Democritus said, but by some kind of operation. For Democritus maintained
that every operation is by way of a discharge of atoms, as we gather from
De Gener. i, 8. But Aristotle held that the intellect has an operation
which is independent of the body's cooperation. Now nothing corporeal can
make an impression on the incorporeal. And therefore in order to cause
the intellectual operation according to Aristotle, the impression caused
by the sensible does not suffice, but something more noble is required,
for "the agent is more noble than the patient," as he says (De Gener. i,
5). Not, indeed, in the sense that the intellectual operation is effected
in us by the mere intellectual operation is effected in us by the mere
impression of some superior beings, as Plato held; but that the higher
and more noble agent which he calls the active intellect, of which we
have spoken above (Question , Articles ,4) causes the phantasms received from the
senses to be actually intelligible, by a process of abstraction.
According to this opinion, then, on the part of the phantasms,
intellectual knowledge is caused by the senses. But since the phantasms
cannot of themselves affect the passive intellect, and require to be made
actually intelligible by the active intellect, it cannot be said that
sensible knowledge is the total and perfect cause of intellectual
knowledge, but rather that it is in a way the material cause.
Reply to Objection 1: Those words of Augustine mean that we must not expect the
entire truth from the senses. For the light of the active intellect is
needed, through which we achieve the unchangeable truth of changeable
things, and discern things themselves from their likeness.
Reply to Objection 2: In this passage Augustine speaks not of intellectual but of
imaginary knowledge. And since, according to the opinion of Plato, the
imagination has an operation which belongs to the soul only, Augustine,
in order to show that corporeal images are impressed on the imagination,
not by bodies but by the soul, uses the same argument as Aristotle does
in proving that the active intellect must be separate, namely, because
"the agent is more noble than the patient." And without doubt, according
to the above opinion, in the imagination there must needs be not only a
passive but also an active power. But if we hold, according to the
opinion of Aristotle, that the action of the imagination, is an action of
the "composite," there is no difficulty; because the sensible body is
more noble than the organ of the animal, in so far as it is compared to
it as a being in act to a being in potentiality; even as the object
actually colored is compared to the pupil which is potentially colored.
It may, however, be said, although the first impression of the
imagination is through the agency of the sensible, since "fancy is
movement produced in accordance with sensation" (De Anima iii, 3), that
nevertheless there is in man an operation which by synthesis and analysis
forms images of various things, even of things not perceived by the
senses. And Augustine's words may be taken in this sense.
Reply to Objection 3: Sensitive knowledge is not the entire cause of intellectual
knowledge. And therefore it is not strange that intellectual knowledge
should extend further than sensitive knowledge.
Article 7: Whether the intellect can actually understand through the intelligible species of which it is possessed, without turning to the phantasms?
Objection 1: It would seem that the intellect can actually understand through
the intelligible species of which it is possessed, without turning to the
phantasms. For the intellect is made actual by the intelligible species
by which it is informed. But if the intellect is in act, it understands.
Therefore the intelligible species suffices for the intellect to
understand actually, without turning to the phantasms.
Objection 2: Further, the imagination is more dependent on the senses than the
intellect on the imagination. But the imagination can actually imagine in
the absence of the sensible. Therefore much more can the intellect
understand without turning to the phantasms.
Objection 3: There are no phantasms of incorporeal things: for the imagination
does not transcend time and space. If, therefore, our intellect cannot
understand anything actually without turning to the phantasms, it follows
that it cannot understand anything incorporeal. Which is clearly false:
for we understand truth, and God, and the angels.
On the contrary, The Philosopher says (De Anima iii, 7) that "the soul
understands nothing without a phantasm."
I answer that, In the present state of life in which the soul is united
to a passible body, it is impossible for our intellect to understand
anything actually, except by turning to the phantasms. First of all
because the intellect, being a power that does not make use of a
corporeal organ, would in no way be hindered in its act through the
lesion of a corporeal organ, if for its act there were not required the
act of some power that does make use of a corporeal organ. Now sense,
imagination and the other powers belonging to the sensitive part, make
use of a corporeal organ. Wherefore it is clear that for the intellect to
understand actually, not only when it acquires fresh knowledge, but also
when it applies knowledge already acquired, there is need for the act of
the imagination and of the other powers. For when the act of the
imagination is hindered by a lesion of the corporeal organ, for instance
in a case of frenzy; or when the act of the memory is hindered, as in the
case of lethargy, we see that a man is hindered from actually
understanding things of which he had a previous knowledge. Secondly,
anyone can experience this of himself, that when he tries to understand
something, he forms certain phantasms to serve him by way of examples, in
which as it were he examines what he is desirous of understanding. For
this reason it is that when we wish to help someone to understand
something, we lay examples before him, from which he forms phantasms for
the purpose of understanding.
Now the reason of this is that the power of knowledge is proportioned to
the thing known. Wherefore the proper object of the angelic intellect,
which is entirely separate from a body, is an intelligible substance
separate from a body. Whereas the proper object of the human intellect,
which is united to a body, is a quiddity or nature existing in corporeal
matter; and through such natures of visible things it rises to a certain
knowledge of things invisible. Now it belongs to such a nature to exist
in an individual, and this cannot be apart from corporeal matter: for
instance, it belongs to the nature of a stone to be in an individual
stone, and to the nature of a horse to be in an individual horse, and so
forth. Wherefore the nature of a stone or any material thing cannot be
known completely and truly, except in as much as it is known as existing
in the individual. Now we apprehend the individual through the senses and
the imagination. And, therefore, for the intellect to understand actually
its proper object, it must of necessity turn to the phantasms in order to
perceive the universal nature existing in the individual. But if the
proper object of our intellect were a separate form; or if, as the
Platonists say, the natures of sensible things subsisted apart from the
individual; there would be no need for the intellect to turn to the
phantasms whenever it understands.
Reply to Objection 1: The species preserved in the passive intellect exist there
habitually when it does not understand them actually, as we have said
above (Question , Article ). Wherefore for us to understand actually, the fact
that the species are preserved does not suffice; we need further to make
use of them in a manner befitting the things of which they are the
species, which things are natures existing in individuals.
Reply to Objection 2: Even the phantasm is the likeness of an individual thing;
wherefore the imagination does not need any further likeness of the
individual, whereas the intellect does.
Reply to Objection 3: Incorporeal things, of which there are no phantasms, are
known to us by comparison with sensible bodies of which there are
phantasms. Thus we understand truth by considering a thing of which we
possess the truth; and God, as Dionysius says (Div. Nom. i), we know as
cause, by way of excess and by way of remotion. Other incorporeal
substances we know, in the present state of life, only by way of remotion
or by some comparison to corporeal things. And, therefore, when we
understand something about these things, we need to turn to phantasms of
bodies, although there are no phantasms of the things themselves.
Article 8: Whether the judgment of the intellect is hindered through suspension of the sensitive powers?
Objection 1: It would seem that the judgment of the intellect is not hindered
by suspension of the sensitive powers. For the superior does not depend
on the inferior. But the judgment of the intellect is higher than the
senses. Therefore the judgment of the intellect is not hindered through
suspension of the senses.
Objection 2: Further, to syllogize is an act of the intellect. But during
sleep the senses are suspended, as is said in De Somn. et Vigil. i and
yet it sometimes happens to us to syllogize while asleep. Therefore the
judgment of the intellect is not hindered through suspension of the
On the contrary, What a man does while asleep, against the moral law, is
not imputed to him as a sin; as Augustine says (Gen. ad lit. xii, 15).
But this would not be the case if man, while asleep, had free use of his
reason and intellect. Therefore the judgment of the intellect is hindered
by suspension of the senses.
I answer that, As we have said above (Article ), our intellect's proper and proportionate object is the nature of a sensible thing. Now a perfect judgment concerning anything cannot be formed, unless all that pertains to that thing's nature be known; especially if that be ignored which is the term and end of judgment. Now the Philosopher says (De Coel. iii), that "as the end of a practical science is action, so the end of natural science is that which is perceived principally through the senses"; for the smith does not seek knowledge of a knife except for the purpose of action, in order that he may produce a certain individual knife; and in like manner the natural philosopher does not seek to know the nature of a stone and of a horse, save for the purpose of knowing the essential properties of those things which he perceives with his senses. Now it is clear that a smith cannot judge perfectly of a knife unless he knows the action of the knife: and in like manner the natural philosopher cannot judge perfectly of natural things, unless he knows sensible things. But in the present state of life whatever we understand, we know by comparison to natural sensible things. Consequently it is not possible for our intellect to form a perfect judgment, while the senses are suspended, through which sensible things are known to us.
Reply to Objection 1: Although the intellect is superior to the senses,
nevertheless in a manner it receives from the senses, and its first and
principal objects are founded in sensible things. And therefore
suspension of the senses necessarily involves a hindrance to the judgment
of the intellect.
Reply to Objection 2: The senses are suspended in the sleeper through certain
evaporations and the escape of certain exhalations, as we read in De
Somn. et Vigil. iii. And, therefore, according to the amount of such
evaporation, the senses are more or less suspended. For when the amount
is considerable, not only are the senses suspended, but also the
imagination, so that there are no phantasms; thus does it happen,
especially when a man falls asleep after eating and drinking copiously.
If, however, the evaporation be somewhat less, phantasms appear, but
distorted and without sequence; thus it happens in a case of fever. And
if the evaporation be still more attenuated, the phantasms will have a
certain sequence: thus especially does it happen towards the end of sleep
in sober men and those who are gifted with a strong imagination. If the
evaporation be very slight, not only does the imagination retain its
freedom, but also the common sense is partly freed; so that sometimes
while asleep a man may judge that what he sees is a dream, discerning, as
it were, between things, and their images. Nevertheless, the common sense
remains partly suspended; and therefore, although it discriminates some
images from the reality, yet is it always deceived in some particular.
Therefore, while man is asleep, according as sense and imagination are
free, so is the judgment of his intellect unfettered, though not
entirely. Consequently, if a man syllogizes while asleep, when he wakes
up he invariably recognizes a flaw in some respect.