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.
Obj. 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 (Q. 76, A. 1).
Since then our mind understands material things, much more is it able
to understand immaterial things.
Obj. 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 things.
Obj. 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.
Obj. 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 and immaterial.
_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 Matt. 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 (Q. 84, A. 7).
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 active intellect.
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 (Q. 70, A. 1).
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 (Q. 79, A. 4), 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 Obj. 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 Obj. 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 substances.
Reply Obj. 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 Obj. 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 Obj. 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.
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