Article 1 — How the persons are compared with the essence, subsistence, and hypostasis

The first point of inquiry is how the persons are compared with the essence, subsistence, and hypostasis. (Parallel texts: ST I.29.2; In I Sent. 23.1.)

Obj. 1: And it would seem that they are altogether the same. For Augustine says, in On the Trinity 7, that the Greeks mean the same thing when they acknowledge three hypostases in God as the Latins when they acknowledge three persons. (Augustine, On the Trinity 7.4 (PL 42:939–42).) Therefore, “hypostasis” and “person” signify the same thing.

Obj. 2: But it will be replied that “person” differs from “hypostasis” in that the latter signifies an individual of any nature in the genus of substance, while “person” denotes an individual of none but a rational nature.

On the contrary, Boethius says that the Greeks employ the term “hypostasis” to denote only an individual of rational nature. (Boethius, On the Person and the Two Natures 3–4 (PL 64:1343–47).) If, then, “person” signifies an individual of rational nature, hypostasis and person are wholly the same thing.

Obj. 3: Names are taken from the accounts of the realities that they signify. Now, account of individuation is the same in things of a rational nature as in other substances. Therefore, an individual of rational nature should not have a special name before the other individuals in the genus of substance, so that thereby there would be a difference between hypostasis and person.

Obj. 4: The term “subsistence” is taken from subsisting. Now, nothing subsists besides individuals in the genus of substance, in which are both accidents and second substances, namely, genus and species. (Aristotle, Categories 5, 2a13–4b19.) Therefore, only individuals in the genus of substance are subsistences. But an individual in the genus of substance is a hypostasis or person. Therefore, subsistence is the same as hypostasis and person.

Obj. 5: It will be replied that genera and species in the genus of substance subsist, since to subsist belongs to them, according to Boethius in On the Two Natures. (Boethius, On the Person and the Two Natures 3–4 (PL 64:1343–47).)

On the contrary, to subsist is to exist through oneself. Hence, what exists only in another does not subsist. Now, genera and species exist only in something else, for they are only in first substances, and if these latter be removed, nothing of the former can possibly remain. (Aristotle, Categories 5, 2a13–4b19.) Hence, to subsist does not belong to genera and species but only to individuals in the genus of substance, so we must still conclude that subsistence is the same as hypostasis.

Obj. 6: Boethius says that ousia (οὐσία), that is, essence, signifies that which is composed of matter and form. (Boethius, Commentary on Aristotle’s Categories, bk. 1, 191C–195D (PL 64:184, 191–96).) Now, this must be an individual, since matter is the principle of individuation. Therefore, the essence signifies the individual, and thus person, hypostasis, essence, and subsistence are the same.

Obj. 7: The essence is signified by the definition, since a definition makes known what a thing is. Now, the definition of a natural thing, which is composed of matter and form, includes not only the form but also the matter, according to the Philosopher. (Aristotle, Metaphysics 6.1, 1025b28–1026a6; 7.5–6, 1031a7–1032a11; cf. 7.11, 1037a21–b7.) Therefore, the essence is something composed of matter and form.

Obj. 8: It will be replied that the essence denotes the common nature whereas the other three, namely, subsistence, hypostasis, and person, signify an individual in the genus of substance.

On the contrary, universal and particular are to be found in every genus. Now, in other genera there are not different names for the particular and the universal; thus, a quality or a quantity are denominated with the same name, whether it be universal or particular. Neither, therefore, in the genus of substance should there be different names to denote a universal and a particular substance; therefore, one would think that these terms have the same signification.

On the contrary (1), Boethius says, in his commentary on The Categories, that ousia (οὐσία), that is, essence, signifies that which is composed of matter and form; that ousiosis (οὐσίωσις), that is, subsistence, signifies the form; and hypostasis signifies the matter. (Boethius, Commentary on Aristotle’s Categories, bk. 1, 191C–195D (PL 64:184, 191–96); bk. 4, 285D–287D (PL 64:285–87).) Therefore, they differ.

Furthermore (2), the same conclusion would seem to follow from the fact that the same author explains the difference between these terms, in On the Two Natures. (Boethius, On the Person and the Two Natures 3–4 (PL 64:1343–47).)

I answer that the Philosopher says that “substance” may be taken in two ways. (Aristotle, Metaphysics 5.8, 1017b23–26.)

In one sense, it is the ultimate subject itself, what is not predicated of another; and this is the particular within the genus of substance.

In another sense, the form or nature of the subject is called the “substance.”

The reason for this distinction is that several subjects may have a common nature; for example, several men have in common the nature of man. Hence, it was necessary to distinguish that which is one from that which is multiple, for the common nature is signified by the definition, which indicates what a reality is; whence this common nature is called the essence or quiddity (“whatness”).

Therefore, whatsoever a real thing contains pertaining to the common nature is included in the signification of the essence, but this cannot be said of all that is contained in the particular substance. For if whatsoever is in the particular substance were to belong to the common nature, there would be no possible distinction between particular substances of the same nature. Now, that which is in the particular substance besides the common nature is individual matter (which is the principle of singularity), and consequently individual accidents, which determine this same matter.

Accordingly, the essence is compared to the particular substance as a formal part thereof, for instance, human nature in Socrates. Hence, in things composed of matter and form, the essence is not altogether the same thing as the subject, and consequently it is not predicated of the subject; for we do not say that Socrates is the one human nature.

On the other hand, in simple substances, there is no difference between essence and subject, seeing that in them there is no individual matter individuating a common nature, but rather their very essence is a subsistence. This is clear from what the Philosopher says (Aristotle, Metaphysics 7.11, 1037a21–b7.) and from Avicenna, who says that the quiddity of a simple thing is itself simple. (Avicenna, The Metaphysics of the Healing 7.)

Now, two things are proper to the substance that is the subject.

The first is that it needs no external foundation in which it is supported but is supported in itself; therefore, it is said to subsist as existing not in another but through itself. The second is that it is the foundation to accidents by sustaining them, and for this reason it is said to “stand-under.”

Accordingly, the substance that is a subject, inasmuch as it subsists, is called ousiosis (οὐσίωσις) or subsistence, but inasmuch as it stands-under, it is called hypostasis by the Greeks and “first substance” by the Latins. It is clear, then, that hypostasis and substance differ in account but are the same thing in reality.

The essence, however, in material substances is not the same thing as them in reality, nor yet is it altogether diverse, since it is oriented as a formal part; whereas in immaterial substances it is altogether the same thing in reality while differing in account. “Person” adds a definite nature to “hypostasis,” since it is nothing more than a hypostasis of rational nature.

Reply Obj. 1: Inasmuch as “person” adds only the rational nature to the hypostasis, it follows that the hypostasis and the person are absolutely the same thing in a rational nature; thus, seeing that “man” adds “rational” to “animal,” it follows that a rational animal is a man. Hence, Augustine’s statement is true when he says that Greeks mean the same thing when they acknowledge three hypostases in God as the Latins when they acknowledge three persons. (Augustine, On the Trinity 7.4 (PL 42:939–42).)

Reply Obj. 2: The word “hypostasis” in Greek in its proper signification denotes an individual substance of any nature whatsoever, but from common usage it has come to mean only an individual of rational nature.

Reply Obj. 3: Just as it is proper to an individual substance to exist through itself, so is it proper to it to act through itself. For nothing acts but an actual being; for which reason just as heat exists not through itself, so neither does it act through itself, but rather the hot thing heats through its heat. Now, to act through themselves belongs in a more excellent degree to substances of a rational nature than to others, since rational substances alone have dominion over their actions, such that it is in them to act or not to act, whereas other substances are more acted upon than act themselves. Hence, it was fitting that the individual substance of rational nature should have a special name.

Reply Obj. 4: Although nothing subsists but the individual substance which is called a hypostasis, it is not said to subsist for the same reason as it is said to stand-under; it is said to subsist as not existing in another, and to stand-under inasmuch as other things are in it. Hence, if there were a substance that existed through itself without being the subject of an accident, it could be called a subsistence but not a substance.

Reply Obj. 5: Boethius expresses himself according to the opinion of Plato, who held genera and species to be separate subsistent forms devoid of accidents; and in this view, they could be called subsistences but not hypostases. Or we may reply that genera and species are said to subsist not because they themselves subsist but because individuals subsist in their natures, even were all accidents removed from them.

Reply Obj. 6: In material substances, essence denotes something composed of matter and form—not indeed of individual matter but of common matter; for the definition of man, which signifies his essence, includes flesh and bones but not this flesh and these bones. On the other hand, individual matter is included in the signification of hypostasis and subsistence in material things.

Reply Obj. 7: This suffices for the reply to the seventh objection.

Reply Obj. 8: Accidents are not individualized save by their subjects. But substance alone is individualized through itself and its proper principles; hence, it is fitting that only in the genus of substance should the particular have a special name.

Reply to the Sed Contra: The arguments advanced in a contrary sense may be granted. But it must be noted that Boethius in his commentary on The Categories (Boethius, Commentary on Aristotle’s Categories (PL 64:159–294).) takes these terms in a different sense from that in which they are usually employed and as he uses them in his work On the Two Natures. (Boethius, On the Person and the Two Natures: A Treatise Against Eutyches and Nestorius (PL 64:1337–54).) Thus, he applies the term hypostasis to matter as the first principle standing-under, due to which the first substance is enabled to stand under accidents, since a simple form cannot be a subject, as he also says in On the Trinity. (Boethius, On the Trinity 1.2 (PL 64:1250).) Again, he applies the term ousiosis (οὐσίωσις) or subsistence to the form as the principle of being because by it is a thing actual, while he employs ousia (οὐσία) or essence as indicating the composite. Thus, he shows that in material substances both form and matter are essential principles.