QUESTION 88: HOW THE HUMAN SOUL KNOWS WHAT IS ABOVE ITSELF
We must now consider how the human soul knows what is above itself, viz.
immaterial substances. Under this head there are three points of inquiry:
(1) Whether the human soul in the present state of life can understand
the immaterial substances called angels, in themselves?
(2) Whether it can arrive at the knowledge thereof by the knowledge of
(3) Whether God is the first object of our knowledge?
Article 1: Whether the human soul in the present state of life can understand immaterial substances in themselves?
Objection 1: It would seem that the human soul in the present state of life
can understand immaterial substances in themselves. For Augustine (De
Trin. ix, 3) says: "As the mind itself acquires the knowledge of
corporeal things by means of the corporeal senses, so it gains from
itself the knowledge of incorporeal things." But these are the immaterial
substances. Therefore the human mind understands immaterial substances.
Objection 2: Further, like is known by like. But the human mind is more akin
to immaterial than to material things; since its own nature is
immaterial, as is clear from what we have said above (Question , Article ). Since
then our mind understands material things, much more is it able to
understand immaterial things.
Objection 3: Further, the fact that objects which are in themselves most
sensible are not most felt by us, comes from sense being corrupted by
their very excellence. But the intellect is not subject to such a
corrupting influence from its object, as is stated De Anima iii, 4.
Therefore things which are in themselves in the highest degree of
intelligibility, are likewise to us most intelligible. As material
things, however, are intelligible only so far as we make them actually so
by abstracting them from material conditions, it is clear that those
substances are more intelligible in themselves whose nature is
immaterial. Therefore they are much more known to us than are material
Objection 4: Further, the Commentator says (Metaph. ii) that "nature would be
frustrated in its end" were we unable to understand abstract substances,
"because it would have made what in itself is naturally intelligible not
to be understood at all." But in nature nothing is idle or purposeless.
Therefore immaterial substances can be understood by us.
Objection 5: Further, as sense is to the sensible, so is intellect to the
intelligible. But our sight can see all things corporeal, whether
superior and incorruptible; or lower and corruptible. Therefore our
intellect can understand all intelligible substances, even the superior
On the contrary, It is written (Wis. 9:16): "The things that are in
heaven, who shall search out?" But these substances are said to be in
heaven, according to Mt. 18:10, "Their angels in heaven," etc. Therefore
immaterial substances cannot be known by human investigation.
I answer that, In the opinion of Plato, immaterial substances are not
only understood by us, but are the objects we understand first of all.
For Plato taught that immaterial subsisting forms, which he called
"Ideas," are the proper objects of our intellect, and thus first and "per
se" understood by us; and, further, that material objects are known by
the soul inasmuch as phantasy and sense are mixed up with the mind. Hence
the purer the intellect is, so much the more clearly does it perceive the
intelligible truth of immaterial things.
But in Aristotle's opinion, which experience corroborates, our intellect
in its present state of life has a natural relationship to the natures of
material things; and therefore it can only understand by turning to the
phantasms, as we have said above (Question , Article ). Thus it clearly appears
that immaterial substances which do not fall under sense and imagination,
cannot first and "per se" be known by us, according to the mode of
knowledge which experience proves us to have.
Nevertheless Averroes (Comment. De Anima iii) teaches that in this
present life man can in the end arrive at the knowledge of separate
substances by being coupled or united to some separate substance, which
he calls the "active intellect," and which, being a separate substance
itself, can naturally understand separate substances. Hence, when it is
perfectly united to us so that by its means we are able to understand
perfectly, we also shall be able to understand separate substances, as in
the present life through the medium of the passive intellect united to
us, we can understand material things. Now he said that the active
intellect is united to us, thus. For since we understand by means of both
the active intellect and intelligible objects, as, for instance, we
understand conclusions by principles understood; it is clear that the
active intellect must be compared to the objects understood, either as
the principal agent is to the instrument, or as form to matter. For an
action is ascribed to two principles in one of these two ways; to a
principal agent and to an instrument, as cutting to the workman and the
saw; to a form and its subject, as heating to heat and fire. In both
these ways the active intellect can be compared to the intelligible
object as perfection is to the perfectible, and as act is to
potentiality. Now a subject is made perfect and receives its perfection
at one and the same time, as the reception of what is actually visible
synchronizes with the reception of light in the eye. Therefore the
passive intellect receives the intelligible object and the active
intellect together; and the more numerous the intelligible objects
received, so much the nearer do we come to the point of perfect union
between ourselves and the active intellect; so much so that when we
understand all the intelligible objects, the active intellect becomes one
with us, and by its instrumentality we can understand all things material
and immaterial. In this he makes the ultimate happiness of man to
consist. Nor, as regards the present inquiry, does it matter whether the
passive intellect in that state of happiness understands separate
substances by the instrumentality of the active intellect, as he himself
maintains, or whether (as he says Alexander holds) the passive intellect
can never understand separate substances (because according to him it is
corruptible), but man understands separate substances by means of the
This opinion, however, is untrue. First, because, supposing the active
intellect to be a separate substance, we could not formally understand by
its instrumentality, for the medium of an agent's formal action consists
in its form and act, since every agent acts according to its actuality,
as was said of the passive intellect (Question , Article ). Secondly, this
opinion is untrue, because in the above explanation, the active
intellect, supposing it to be a separate substance, would not be joined
to us in its substance, but only in its light, as participated in things
understood; and would not extend to the other acts of the active
intellect so as to enable us to understand immaterial substances; just as
when we see colors set off by the sun, we are not united to the substance
of the sun so as to act like the sun, but its light only is united to us,
that we may see the colors. Thirdly, this opinion is untrue, because
granted that, as above explained, the active intellect were united to us
in substance, still it is not said that it is wholly so united in regard
to one intelligible object, or two; but rather in regard to all
intelligible objects. But all such objects together do not equal the
force of the active intellect, as it is a much greater thing to
understand separate substances than to understand all material things.
Hence it clearly follows that the knowledge of all material things would
not make the active intellect to be so united to us as to enable us by
its instrumentality to understand separate substances.
Fourthly, this opinion is untrue, because it is hardly possible for
anyone in this world to understand all material things: and thus no one,
or very few, could reach to perfect felicity; which is against what the
Philosopher says (Ethic. i, 9), that happiness is a "kind of common good,
communicable to all capable of virtue." Further, it is unreasonable that
only the few of any species attain to the end of the species.
Fifthly, the Philosopher expressly says (Ethic. i, 10), that happiness
is "an operation according to perfect virtue"; and after enumerating many
virtues in the tenth book, he concludes (Ethic. i, 7) that ultimate
happiness consisting in the knowledge of the highest things intelligible
is attained through the virtue of wisdom, which in the sixth chapter he
had named as the chief of speculative sciences. Hence Aristotle clearly
places the ultimate felicity of man in the knowledge of separate
substances, obtainable by speculative science; and not by being united to
the active intellect as some imagined.
Sixthly, as was shown above (Question , Article ), the active intellect is not a
separate substance; but a faculty of the soul, extending itself actively
to the same objects to which the passive intellect extends receptively;
because, as is stated (De Anima iii, 5), the passive intellect is "all
things potentially," and the active intellect is "all things in act."
Therefore both intellects, according to the present state of life, extend
to material things only, which are made actually intelligible by the
active intellect, and are received in the passive intellect. Hence in the
present state of life we cannot understand separate immaterial substances
in themselves, either by the passive or by the active intellect.
Reply to Objection 1: Augustine may be taken to mean that the knowledge of
incorporeal things in the mind can be gained by the mind itself. This is
so true that philosophers also say that the knowledge concerning the soul
is a principle for the knowledge of separate substances. For by knowing
itself, it attains to some knowledge of incorporeal substances, such as
is within its compass; not that the knowledge of itself gives it a
perfect and absolute knowledge of them.
Reply to Objection 2: The likeness of nature is not a sufficient cause of
knowledge; otherwise what Empedocles said would be true ---that the soul
needs to have the nature of all in order to know all. But knowledge
requires that the likeness of the thing known be in the knower, as a kind
of form thereof. Now our passive intellect, in the present state of
life, is such that it can be informed with similitudes abstracted from
phantasms: and therefore it knows material things rather than immaterial
Reply to Objection 3: There must needs be some proportion between the object and
the faculty of knowledge; such as of the active to the passive, and of
perfection to the perfectible. Hence that sensible objects of great power
are not grasped by the senses, is due not merely to the fact that they
corrupt the organ, but also to their being improportionate to the
sensitive power. And thus it is that immaterial substances are
improportionate to our intellect, in our present state of life, so that
it cannot understand them.
Reply to Objection 4: This argument of the Commentator fails in several ways.
First, because if separate substances are not understood by us, it does
not follow that they are not understood by any intellect; for they are
understood by themselves, and by one another.
Secondly, to be understood by us is not the end of separate substances:
while only that is vain and purposeless, which fails to attain its end.
It does not follow, therefore, that immaterial substances are
purposeless, even if they are not understood by us at all.
Reply to Objection 5: Sense knows bodies, whether superior or inferior, in the
same way, that is, by the sensible acting on the organ. But we do not
understand material and immaterial substances in the same way. The former
we understand by a process of abstraction, which is impossible in the
case of the latter, for there are no phantasms of what is immaterial.
Article 2: Whether our intellect can understand immaterial substances through its knowledge of material things?
Objection 1: It would seem that our intellect can know immaterial substances
through the knowledge of material things. For Dionysius says (Coel. Hier.
i) that "the human mind cannot be raised up to immaterial contemplation
of the heavenly hierarchies, unless it is led thereto by material
guidance according to its own nature." Therefore we can be led by
material things to know immaterial substances.
Objection 2: Further, science resides in the intellect. But there are sciences
and definitions of immaterial substances; for Damascene defines an angel
(De Fide Orth. ii, 3); and we find angels treated of both in theology and
philosophy. Therefore immaterial substances can be understood by us.
Objection 3: Further, the human soul belongs to the genus of immaterial
substances. But it can be understood by us through its act by which it
understands material things. Therefore also other material substances can
be understood by us, through their material effects.
Objection 4: Further, the only cause which cannot be comprehended through its
effects is that which is infinitely distant from them, and this belongs
to God alone. Therefore other created immaterial substances can be
understood by us through material things.
On the contrary, Dionysius says (Div. Nom. i) that "intelligible things
cannot be understood through sensible things, nor composite things
through simple, nor incorporeal through corporeal."
I answer that, Averroes says (De Anima iii) that a philosopher named
Avempace [*Ibn-Badja, Arabian Philosopher; ob. 1183] taught that by the
understanding of natural substances we can be led, according to true
philosophical principles, to the knowledge of immaterial substances. For
since the nature of our intellect is to abstract the quiddity of material
things from matter, anything material residing in that abstracted
quiddity can again be made subject to abstraction; and as the process of
abstraction cannot go on forever, it must arrive at length at some
immaterial quiddity, absolutely without matter; and this would be the
understanding of immaterial substance.
Now this opinion would be true, were immaterial substances the forms and
species of these material things; as the Platonists supposed. But
supposing, on the contrary, that immaterial substances differ altogether
from the quiddity of material things, it follows that however much our
intellect abstract the quiddity of material things from matter, it could
never arrive at anything akin to immaterial substance. Therefore we are
not able perfectly to understand immaterial substances through material
Reply to Objection 1: From material things we can rise to some kind of knowledge
of immaterial things, but not to the perfect knowledge thereof; for there
is no proper and adequate proportion between material and immaterial
things, and the likenesses drawn from material things for the
understanding of immaterial things are very dissimilar therefrom, as
Dionysius says (Coel. Hier. ii).
Reply to Objection 2: Science treats of higher things principally by way of
negation. Thus Aristotle (De Coel. i, 3) explains the heavenly bodies by
denying to them inferior corporeal properties. Hence it follows that much
less can immaterial substances be known by us in such a way as to make us
know their quiddity; but we may have a scientific knowledge of them by
way of negation and by their relation to material things.
Reply to Objection 3: The human soul understands itself through its own act of understanding, which is proper to it, showing perfectly its power and nature. But the power and nature of immaterial substances cannot be perfectly known through such act, nor through any other material thing, because there is no proportion between the latter and the power of the former.
Reply to Objection 4: Created immaterial substances are not in the same natural
genus as material substances, for they do not agree in power or in
matter; but they belong to the same logical genus, because even
immaterial substances are in the predicament of substance, as their
essence is distinct from their existence. But God has no connection with
material things, as regards either natural genus or logical genus;
because God is in no genus, as stated above (Question , Article ). Hence through
the likeness derived from material things we can know something positive
concerning the angels, according to some common notion, though not
according to the specific nature; whereas we cannot acquire any such
knowledge at all about God.
Article 3: Whether God is the first object known by the human mind?
Objection 1: It would seem that God is the first object known by the human
mind. For that object in which all others are known, and by which we
judge others, is the first thing known to us; as light is to the eye, and
first principles to the intellect. But we know all things in the light of
the first truth, and thereby judge of all things, as Augustine says (De
Trin. xii, 2; De Vera Relig. xxxi; [*Confess. xii, 25]). Therefore God is
the first object known to us.
Objection 2: Further, whatever causes a thing to be such is more so. But God
is the cause of all our knowledge; for He is "the true light which
enlighteneth every man that cometh into this world" (Jn. 1:9). Therefore
God is our first and most known object.
Objection 3: Further, what is first known in the image is the exemplar to
which it is made. But in our mind is the image of God, as Augustine says
(De Trin. xii, 4,7). Therefore God is the first object known to our mind.
On the contrary, "No man hath seen God at any time" (Jn. 1:18).
I answer that, Since the human intellect in the present state of life cannot understand even immaterial created substances (Article ), much less can it understand the essence of the uncreated substance. Hence it must be said simply that God is not the first object of our knowledge. Rather do we know God through creatures, according to the Apostle (Rm. 1:20), "the invisible things of God are clearly seen, being understood by the things that are made": while the first object of our knowledge in this life is the "quiddity of a material thing," which is the proper object of our intellect, as appears above in many passages (Question , Article ; Question , Article ; Question , Article , ad 2)
Reply to Objection 1: We see and judge of all things in the light of the first
truth, forasmuch as the light itself of our mind, whether natural or
gratuitous, is nothing else than the impression of the first truth upon
it, as stated above (Question , Article ). Hence, as the light itself of our
intellect is not the object it understands, much less can it be said that
God is the first object known by our intellect.
Reply to Objection 2: The axiom, "Whatever causes a thing to be such is more so,"
must be understood of things belonging to one and the same order, as
explained above (Question , Article , ad 3). Other things than God are known
because of God; not as if He were the first known object, but because He
is the first cause of our faculty of knowledge.
Reply to Objection 3: If there existed in our souls a perfect image of God, as
the Son is the perfect image of the Father, our mind would know God at
once. But the image in our mind is imperfect; hence the argument does not