Whether "Person" Is the Same As Hypostasis, Subsistence, and Essence?
Objection 1: It would seem that "person" is the same as "hypostasis,"
"subsistence," and "essence." For Boethius says (De Duab. Nat.) that
"the Greeks called the individual substance of the rational nature by
the name hypostasis." But this with us signifies "person." Therefore
"person" is altogether the same as "hypostasis."
Obj. 2: Further, as we say there are three persons in God, so we say
there are three subsistences in God; which implies that "person" and
"subsistence" have the same meaning. Therefore "person" and
"subsistence" mean the same.
Obj. 3: Further, Boethius says (Com. Praed.) that the Greek _ousia,_
which means essence, signifies a being composed of matter and form.
Now that which is composed of matter and form is the individual
substance called "hypostasis" and "person." Therefore all the
aforesaid names seem to have the same meaning.
Obj. 4: _On the contrary,_ Boethius says (De Duab. Nat.) that genera
and species only subsist; whereas individuals are not only
subsistent, but also substand. But subsistences are so called from
subsisting, as substance or hypostasis is so called from substanding.
Therefore, since genera and species are not hypostases or persons,
these are not the same as subsistences.
Obj. 5: Further, Boethius says (Com. Praed.) that matter is called
hypostasis, and form is called _ousiosis_--that is, subsistence. But
neither form nor matter can be called person. Therefore person
differs from the others.
_I answer that,_ According to the Philosopher (Metaph. v), substance
is twofold. In one sense it means the quiddity of a thing, signified
by its definition, and thus we say that the definition means the
substance of a thing; in which sense substance is called by the
Greeks _ousia,_ what we may call "essence." In another sense
substance means a subject or _suppositum,_ which subsists in the
genus of substance. To this, taken in a general sense, can be
applied a name expressive of an intention; and thus it is called
_suppositum._ It is also called by three names signifying a
reality--that is, "a thing of nature," "subsistence," and
"hypostasis," according to a threefold consideration of the substance
thus named. For, as it exists in itself and not in another, it is
called "subsistence"; as we say that those things subsist which exist
in themselves, and not in another. As it underlies some common
nature, it is called "a thing of nature"; as, for instance, this
particular man is a human natural thing. As it underlies the
accidents, it is called "hypostasis," or "substance." What these
three names signify in common to the whole genus of substances, this
name "person" signifies in the genus of rational substances.
Reply Obj. 1: Among the Greeks the term "hypostasis," taken in the
strict interpretation of the word, signifies any individual of the
genus substance; but in the usual way of speaking, it means the
individual of the rational nature, by reason of the excellence of
that nature.
Reply Obj. 2: As we say "three persons" plurally in God, and "three
subsistences," so the Greeks say "three hypostases." But because the
word "substance," which, properly speaking, corresponds in meaning to
"hypostasis," is used among us in an equivocal sense, since it
sometimes means essence, and sometimes means hypostasis, in order to
avoid any occasion of error, it was thought preferable to use
"subsistence" for hypostasis, rather than "substance."
Reply Obj. 3: Strictly speaking, the essence is what is expressed by
the definition. Now, the definition comprises the principles of the
species, but not the individual principles. Hence in things composed
of matter and form, the essence signifies not only the form, nor only
the matter, but what is composed of matter and the common form, as
the principles of the species. But what is composed of this matter
and this form has the nature of hypostasis and person. For soul,
flesh, and bone belong to the nature of man; whereas this soul, this
flesh and this bone belong to the nature of this man. Therefore
hypostasis and person add the individual principles to the idea of
essence; nor are these identified with the essence in things composed
of matter and form, as we said above when treating of divine
simplicity (Q. 3, A. 3).
Reply Obj. 4: Boethius says that genera and species subsist, inasmuch
as it belongs to some individual things to subsist, from the fact
that they belong to genera and species comprised in the predicament
of substance, but not because the species and genera themselves
subsist; except in the opinion of Plato, who asserted that the
species of things subsisted separately from singular things. To
substand, however, belongs to the same individual things in relation
to the accidents, which are outside the essence of genera and species.
Reply Obj. 5: The individual composed of matter and form substands in
relation to accident from the very nature of matter. Hence Boethius
says (De Trin.): "A simple form cannot be a subject." Its
self-subsistence is derived from the nature of its form, which does
not supervene to the things subsisting, but gives actual existence to
the matter and makes it subsist as an individual. On this account,
therefore, he ascribes hypostasis to matter, and _ousiosis,_ or
subsistence, to the form, because the matter is the principle of
substanding, and form is the principle of subsisting.
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