QUESTION 86: WHAT OUR INTELLECT KNOWS IN MATERIAL THINGS
We now have to consider what our intellect knows in material things.
Under this head there are four points of inquiry:
(1) Whether it knows singulars?
(2) Whether it knows the infinite?
(3) Whether it knows contingent things?
(4) Whether it knows future things?
Article 1: Whether our intellect knows singulars?
Objection 1: It would seem that our intellect knows singulars. For whoever
knows composition, knows the terms of composition. But our intellect
knows this composition; "Socrates is a man": for it belongs to the
intellect to form a proposition. Therefore our intellect knows this
Objection 2: Further, the practical intellect directs to action. But action
has relation to singular things. Therefore the intellect knows the
Objection 3: Further, our intellect understands itself. But in itself it is a
singular, otherwise it would have no action of its own; for actions
belong to singulars. Therefore our intellect knows singulars.
Objection 4: Further, a superior power can do whatever is done by an inferior
power. But sense knows the singular. Much more, therefore, can the
intellect know it.
On the contrary, The Philosopher says (Phys. i, 5), that "the universal
is known by reason; and the singular is known by sense."
I answer that, Our intellect cannot know the singular in material things directly and primarily. The reason of this is that the principle of singularity in material things is individual matter, whereas our intellect, as have said above (Question , Article ), understands by abstracting the intelligible species from such matter. Now what is abstracted from individual matter is the universal. Hence our intellect knows directly the universal only. But indirectly, and as it were by a kind of reflection, it can know the singular, because, as we have said above (Question , Article ), even after abstracting the intelligible species, the intellect, in order to understand, needs to turn to the phantasms in which it understands the species, as is said De Anima iii, 7. Therefore it understands the universal directly through the intelligible species, and indirectly the singular represented by the phantasm. And thus it forms the proposition "Socrates is a man." Wherefore the reply to the first objection is clear.
Reply to Objection 2: The choice of a particular thing to be done is as the
conclusion of a syllogism formed by the practical intellect, as is said
Ethic. vii, 3. But a singular proposition cannot be directly concluded
from a universal proposition, except through the medium of a singular
proposition. Therefore the universal principle of the practical intellect
does not move save through the medium of the particular apprehension of
the sensitive part, as is said De Anima iii, 11.
Reply to Objection 3: Intelligibility is incompatible with the singular not as
such, but as material, for nothing can be understood otherwise than
immaterially. Therefore if there be an immaterial singular such as the
intellect, there is no reason why it should not be intelligible.
Reply to Objection 4: The higher power can do what the lower power can, but in a
more eminent way. Wherefore what the sense knows materially and
concretely, which is to know the singular directly, the intellect knows
immaterially and in the abstract, which is to know the universal.
Article 2: Whether our intellect can know the infinite?
Objection 1: It would seem that our intellect can know the infinite. For God
excels all infinite things. But our intellect can know God, as we have
said above (Question , Article ). Much more, therefore, can our intellect know
all other infinite things.
Objection 2: Further, our intellect can naturally know "genera" and "species."
But there is an infinity of species in some genera, as in number,
proportion, and figure. Therefore our intellect can know the infinite.
Objection 3: Further, if one body can coexist with another in the same place,
there is nothing to prevent an infinite number of bodies being in one
place. But one intelligible species can exist with another in the same
intellect, for many things can be habitually known at the same time.
Therefore our intellect can have an habitual knowledge of an infinite
number of things.
Objection 4: Further, as the intellect is not a corporeal faculty, as we have
said (Question , Article ), it appears to be an infinite power. But an infinite
power has a capacity for an infinite object. Therefore our intellect can
know the infinite.
On the contrary, It is said (Phys. i, 4) that "the infinite, considered
as such, is unknown."
I answer that, Since a faculty and its object are proportional to each
other, the intellect must be related to the infinite, as is its object,
which is the quiddity of a material thing. Now in material things the
infinite does not exist actually, but only potentially, in the sense of
one succeeding another, as is said Phys. iii, 6. Therefore infinity is
potentially in our mind through its considering successively one thing
after another: because never does our intellect understand so many
things, that it cannot understand more.
On the other hand, our intellect cannot understand the infinite either
actually or habitually. Not actually, for our intellect cannot know
actually at the same time, except what it knows through one species. But
the infinite is not represented by one species, for if it were it would
be something whole and complete. Consequently it cannot be understood
except by a successive consideration of one part after another, as is
clear from its definition (Phys. iii, 6): for the infinite is that "from
which, however much we may take, there always remains something to be
taken." Thus the infinite could not be known actually, unless all its
parts were counted: which is impossible.
For the same reason we cannot have habitual knowledge of the infinite:
because in us habitual knowledge results from actual consideration: since
by understanding we acquire knowledge, as is said Ethic. ii, 1. Wherefore
it would not be possible for us to have a habit of an infinity of things
distinctly known, unless we had already considered the entire infinity
thereof, counting them according to the succession of our knowledge:
which is impossible. And therefore neither actually nor habitually can
our intellect know the infinite, but only potentially as explained above.
Reply to Objection 1: As we have said above (Question , Article ), God is called infinite,
because He is a form unlimited by matter; whereas in material things, the
term 'infinite' is applied to that which is deprived of any formal term.
And form being known in itself, whereas matter cannot be known without
form, it follows that the material infinite is in itself unknowable. But
the formal infinite, God, is of Himself known; but He is unknown to us by
reason of our feeble intellect, which in its present state has a natural
aptitude for material objects only. Therefore we cannot know God in our
present life except through material effects. In the future life this
defect of intellect will be removed by the state of glory, when we shall
be able to see the Essence of God Himself, but without being able to
Reply to Objection 2: The nature of our mind is to know species abstracted from
phantasms; therefore it cannot know actually or habitually species of
numbers or figures that are not in the imagination, except in a general
way and in their universal principles; and this is to know them
potentially and confusedly.
Reply to Objection 3: If two or more bodies were in the same place, there would
be no need for them to occupy the place successively, in order for the
things placed to be counted according to this succession of occupation.
On the other hand, the intelligible species enter into our intellect
successively; since many things cannot be actually understood at the same
time: and therefore there must be a definite and not an infinite number
of species in our intellect.
Reply to Objection 4: As our intellect is infinite in power, so does it know the
infinite. For its power is indeed infinite inasmuch as it is not
terminated by corporeal matter. Moreover it can know the universal, which
is abstracted from individual matter, and which consequently is not
limited to one individual, but, considered in itself, extends to an
infinite number of individuals.
Article 3: Whether our intellect can know contingent things?
Objection 1: It would seem that the intellect cannot know contingent things:
because, as the Philosopher says (Ethic. vi, 6), the objects of
understanding, wisdom and knowledge are not contingent, but necessary
Objection 2: Further, as stated in Phys. iv, 12, "what sometimes is and
sometimes is not, is measured by time." Now the intellect abstracts from
time, and from other material conditions. Therefore, as it is proper to a
contingent thing sometime to be and sometime not to be, it seems that
contingent things are not known by the intellect.
On the contrary, All knowledge is in the intellect. But some sciences
are of the contingent things, as the moral sciences, the objects of which
are human actions subject to free-will; and again, the natural sciences
in as far as they relate to things generated and corruptible. Therefore
the intellect knows contingent things.
I answer that, Contingent things can be considered in two ways; either
as contingent, or as containing some element of necessity, since every
contingent thing has in it something necessary: for example, that
Socrates runs, is in itself contingent; but the relation of running to
motion is necessary, for it is necessary that Socrates move if he runs.
Now contingency arises from matter, for contingency is a potentiality to
be or not to be, and potentiality belongs to matter; whereas necessity
results from form, because whatever is consequent on form is of necessity
in the subject. But matter is the individualizing principle: whereas the
universal comes from the abstraction of the form from the particular
matter. Moreover it was laid down above (Article ) that the intellect of
itself and directly has the universal for its object; while the object of
sense is the singular, which in a certain way is the indirect object of
the intellect, as we have said above (Article ). Therefore the contingent,
considered as such, is known directly by sense and indirectly by the
intellect; while the universal and necessary principles of contingent
things are known only by the intellect. Hence if we consider the objects
of science in their universal principles, then all science is of
necessary things. But if we consider the things themselves, thus some
sciences are of necessary things, some of contingent things.
From which the replies to the objections are clear.
Article 4: Whether our intellect can know the future?
Objection 1: It would seem that our intellect knows the future. For our
intellect knows by means of intelligible species abstracted from the
"here" and "now," and related indifferently to all time. But it can know
the present. Therefore it can know the future.
Objection 2: Further, man, while his senses are in suspense, can know some
future things, as in sleep, and in frenzy. But the intellect is freer and
more vigorous when removed from sense. Therefore the intellect of its own
nature can know the future.
Objection 3: The intellectual knowledge of man is superior to any knowledge of
brutes. But some animals know the future; thus crows by their frequent
cawing foretell rain. Therefore much more can the intellect know the
On the contrary, It is written (Eccles. 8:6,7), "There is a great
affliction for man, because he is ignorant of things past; and things to
come he cannot know by any messenger."
I answer that, We must apply the same distinction to future things, as
we applied above (Article ) to contingent things. For future things
considered as subject to time are singular, and the human intellect knows
them by reflection only, as stated above (Article ). But the principles of
future things may be universal; and thus they may enter the domain of the
intellect and become the objects of science.
Speaking, however, of the knowledge of the future in a general way, we
must observe that the future may be known in two ways: either in itself,
or in its cause. The future cannot be known in itself save by God alone;
to Whom even that is present which in the course of events is future,
forasmuch as from eternity His glance embraces the whole course of time,
as we have said above when treating of God's knowledge (Question , Article ).
But forasmuch as it exists in its cause, the future can be known by us
also. And if, indeed, the cause be such as to have a necessary connection
with its future result, then the future is known with scientific
certitude, just as the astronomer foresees the future eclipse. If,
however, the cause be such as to produce a certain result more frequently
than not, then can the future be known more or less conjecturally,
according as its cause is more or less inclined to produce the effect.
Reply to Objection 1: This argument considers that knowledge which is drawn from
universal causal principles; from these the future may be known,
according to the order of the effects to the cause.
Reply to Objection 2: As Augustine says (Confess. xii [*Gen. ad lit. xii. 13]),
the soul has a certain power of forecasting, so that by its very nature
it can know the future; hence when withdrawn from corporeal sense, and,
as it were, concentrated on itself, it shares in the knowledge of the
future. Such an opinion would be reasonable if we were to admit that the
soul receives knowledge by participating the ideas as the Platonists
maintained, because in that case the soul by its nature would know the
universal causes of all effects, and would only be impeded in its
knowledge by the body, and hence when withdrawn from the corporeal senses
it would know the future.
But since it is connatural to our intellect to know things, not thus,
but by receiving its knowledge from the senses; it is not natural for the
soul to know the future when withdrawn from the senses: rather does it
know the future by the impression of superior spiritual and corporeal
causes; of spiritual causes, when by Divine power the human intellect is
enlightened through the ministry of angels, and the phantasms are
directed to the knowledge of future events; or, by the influence of
demons, when the imagination is moved regarding the future known to the
demons, as explained above (Question , Article ). The soul is naturally more
inclined to receive these impressions of spiritual causes when it is
withdrawn from the senses, as it is then nearer to the spiritual world,
and freer from external distractions. The same may also come from
superior corporeal causes. For it is clear that superior bodies influence
inferior bodies. Hence, in consequence of the sensitive faculties being
acts of corporeal organs, the influence of the heavenly bodies causes the
imagination to be affected, and so, as the heavenly bodies cause many
future events, the imagination receives certain images of some such
events. These images are perceived more at night and while we sleep than
in the daytime and while we are awake, because, as stated in De Somn. et
Vigil. ii [*De Divinat. per somn. ii.], "impressions made by day are
evanescent. The night air is calmer, when silence reigns, hence bodily
impressions are made in sleep, when slight internal movements are felt
more than in wakefulness, and such movements produce in the imagination
images from which the future may be foreseen."
Reply to Objection 3: Brute animals have no power above the imagination wherewith
to regulate it, as man has his reason, and therefore their imagination
follows entirely the influence of the heavenly bodies. Thus from such
animals' movements some future things, such as rain and the like, may be
known rather from human movements directed by reason. Hence the
Philosopher says (De Somn. et Vig.), that "some who are most imprudent
are most far-seeing; for their intelligence is not burdened with cares,
but is as it were barren and bare of all anxiety moving at the caprice of
whatever is brought to bear on it."