The types of composition in
creatures distinguished by Aquinas
After
distinguishing the two senses of ‘being’ (for an explanation of this
distinction check my lecture-note ‘Aquinas on Being and Essence’), and
pointing out that it is only beings in the primary sense that have essence,
since essence is precisely the determination of an act of being signified by
the term ‘being’ in this sense, Aquinas goes on to show that the essence of a
material substance itself has to contain matter somehow. The reason why there
has to be matter in their essence is that the essence of a thing is what is
signified by the thing’s quidditative definition, the definition consisting of
the thing’s genus and specific difference, which, in turn are definable further
in terms of the more and more universal differences and genera, climbing up the
Porphyrian tree. But in the last analysis any such
definition of any material substance has to contain the difference ‘material’.
Therefore, at least this part of all these definitions signifies matter
somehow, and thus, the definition itself, which signifies the whole essence of
the thing, signifies matter as a part of this essence. (The other part is
substantial form, conceived as that which informs this matter, giving it its
substantial being.) But since the definition signifies matter in this way only
in a universal manner, and never the particular, designated matter of this or
that individual as such, the essence of a material substance contains matter
only in this universal manner. Such an essence, therefore, contains matter only
in general, but of course this does not mean that it should contain some
“general matter”. There is no such a thing as “general matter”, there is only
particular matter; but this can be conceived in a universal manner, and it is
matter thus conceived that is said to be a part of a material essence.
On
the other hand, what really exists in things is only particular, designated
matter, that is, matter here and now, considered under the particular
dimensions of the extension of this particular body. It is this matter,
considered as such, which Aquinas identifies as the principle of individuation in material
substances. This matter is obviously merely conceptually distinct from the
matter considered in general, which is conceived as a part of the essence of
this thing. But this particular matter is really distinct from the essence of
the same thing itself, for it is precisely this particular matter that is
excluded from the concept of essence, as it is signified by the abstract form
of an essential predicate of the thing. (That is to say, as it is signified by
the term ‘humanity’, the abstract form of the essential predicate ‘man’.
Concerning the difference between a real distinction as opposed to a merely
conceptual distinction or distinction of reason, see
the handout accompanying the lecture note on Aquinas.)
On the other hand, Aquinas also argues that the different essential predicates
of the same particular thing do not signify really distinct forms in the same
thing. This is Aquinas’ famous doctrine of the unity of substantial forms: in
one and the same thing it is one and the same substantial form that verifies of
this thing all the essential predicates of the thing. (Thus, here we also have
a merely conceptual distinction between the forms signified by the different
substantial predicates of the same thing: the predicates arranged on the Porphyrian tree signify one and the same form in the same
thing, but they signify this form according to different, more or less abstract,
and consequently more or less universal concepts. Note here that Aquinas
sometimes also refers to a concept by the term ‘intention’. In this context
‘concept’ and ‘intention’ mean the same: (the direct, immediate object of) an act
of mind on account of which the mind has some abstract, universal cognition of
several particulars.)
On
the basis of these considerations, we have to say that material substances are
composite in several ways, depending on how we consider and identify their
various integral parts.
1. They are composed of matter
and (substantial) form, as is obvious
2. Their essence itself is also
composed of matter and form considered in general
3. They are also composed of
their essence (which comprises their matter and form in general) and their
individual, designated matter, which is the principle of their individuation,
i.e., that on account of which one individual of the same species is numerically
distinct from another individual of the same species.
These
three types of composition are peculiar to material substances, since all of
these are the result of their having matter, informed by their substantial
form.
But
they also exhibit two further sorts of composition, which they share even with
immaterial substances, except for God. These are
4. The composition from subject
and accident
5. The composition of essence
and existence (potentiality and actuality)
The
former type of composition is present even in angels (“intelligences”, as
Aquinas also refers to them), given the fact that even angels are changeable in
respect of their spiritual activity, say, changing the objects of their thought
or their will. It is only God, who is eternally immutable, self-thinking
thought, who knows of all changeable things by understanding His own nature,
which is only fragmentarily and imperfectly represented by the finite natures
of His creatures, just as the light of the sun can be reflected by several,
brighter and dimmer, variously tinted mirrors.
The
second type of composition also has to be present in all creatures given that
their essence is really distinct from their existence (this fundamental
Thomistic thesis is often referred to as “the thesis of real distinction”
[between essence and existence in creatures]). It is only God whose essence is
nothing but His existence, which is precisely the reason why His essence, not
being distinct from His existence, does not put any limitation on the infinite
actuality of His existence. By contrast, the essences of creatures, even of the
highest-ranking angels, are some determination of the act of existence which
actualizes this essence. Indeed, given that angels cannot be numerically
different on account of their designated matter (since they are immaterial),
they differ from one another in their essence, that is, in virtue of the
differences between how much limitation their essence imposes upon their
existence: thus they differ in their essential perfection, and so they have to
differ not only numerically but also specifically; according to Thomas,
therefore, there cannot be two angels of the same species.
It
is possible, however, to have several human souls of the same species, despite
the fact that according to Aquinas, human souls are also immaterial substances.
However, they are immaterial not in exactly the same sense in which separate
substances are immaterial. Separate substances (angels and God) are immaterial
in the sense that their being is in no way the actuality of any parcel of
matter. The human soul, however, acquires its being in some parcel of matter,
yet it is immaterial in that it is not dependent for its continued existence
upon actually informing any matter. This is why it is possible for human souls
to multiply in the same species according the multiplicity of human bodies they
inform, and to continue in their individual existence even after they get
separated from the human body upon the death of a human person. (Check Aquinas
quoting Avicenna for this solution.)
It
is this different interpretation of the immateriality of the human soul that
allows Aquinas to avoid the otherwise apparently inevitable Averroist
conclusion according to which there is only one human intellect, a separate
substance, which is united with humans only in its operation, by using
individual humans’ phantasms for its thinking. But by insisting that the human
intellect has to be united with the body not only in its operation, but also in
its being, Aquinas can maintain the numerical multiplication of human
intellects, and thus he can avoid the further unorthodox implications of the
Averroist position.