Article 2 — What a person is

The second point of inquiry is what a person is. (Parallel texts: ST I.29.1; I.29.3, ad 2, ad 4; III.2.2; In I Sent. 25.1; De unione Verbi Incarnati, a. 1.)

Obj. 1: Boethius, in On the Two Natures, defines it as an individual substance of a rational nature, (Boethius, On the Person and the Two Natures 3 (PL 64:1343); cf. 2–4 (PL 64:1342–47).) and it would seem that this definition is incorrect. For, according to the Philosopher, no singular thing can be defined. (Aristotle, Metaphysics 7.10, 1035b33–1036a10.) Now, a person is a singular within the genus of substance, as already stated. Therefore, it cannot be defined.

Obj. 2: To this it will be replied that, although that which is a person is a singular, the account of a person is something common, and this suffices to make it possible to define it.

On the contrary, that which is common to every individual substance of rational nature is the intention of singularity, which is not in the genus of substance. Therefore, in the definition of person we should not give substance as the genus.

Obj. 3: But it will be replied that this word “person” does not denote a mere intention, but an intention together with its subject.

On the contrary, the Philosopher proves that a compound of subject and accident cannot be defined, because such a definition would be nugatory. (Aristotle, Metaphysics 7.3–4, 1029a20–1030a17; 7.5, 1030b14–1031a14.) For seeing that the definition of an accident includes the subject, for example, nose in the definition of “snub,” it will be necessary in defining a compound of subject and accident to express the subject twice, once for itself and once for the accident. If, then, “person” signifies the intention together with the subject, it will be futile to define it.

Obj. 4: The subject of this common intention is an individual. If, then, “person” denotes the intention together with its subject, it will still follow that, in defining person, the individual will be defined, which cannot be done.

Obj. 5: An intention is not included in the definition of a real thing, nor accident in the definition of a substance. Now, “person” denominates a real thing and a substance. Therefore, it is unfitting to include “individual” in the definition of “person,” since it denotes both an intention and an accident.

Obj. 6: A thing in whose definition substance is expressed as the genus must be itself a species of substance. Now, person is not a species of substance, for then it would be condivided with other species of substance. Therefore, it is unfitting in defining person to express substance as the genus.

Obj. 7: “Substance” is divided into first and second. Now, second substance cannot be placed in the definition of person, for a contradiction of terms would be involved when it is called an “individual substance,” for second substance is universal substance. But likewise, neither is “person” the first substance, for a first substance is an individual substance, so it would be futile to add “individual” to “substance” in defining person. Therefore, it is unfitting to include substance in the definition of person.

Obj. 8: The term “subsistence” seems more akin to person than does “substance”; for we say that there are three subsistences in God, as likewise three persons, while we do not say there are three substances, but one. Therefore, it were better to define a person as a subsistence than as a substance.

Obj. 9: If you multiply the thing defined, you multiply the genus included in the definition; thus, many men are many animals. Now, there are three persons and not three substances in God. Therefore, substance should not be expressed as the genus in the definition of person.

Obj. 10: Rational is a difference of animal. Now, person is found in things that are not animals, namely, in the angels and in God. Therefore, rational should not be expressed as the difference in defining person.

Obj. 11: Nature is only in movable things, since it is the principle of movement, as is said in Physics 2. (Aristotle, Physics 2.1, 192b20.) Now, essence is in things both movable and immovable. Therefore, it were better in defining person to include essence rather than nature, seeing that person is found both in movable and immovable things, since person is found in men, angels, and God.

Obj. 12: The definition should be convertible with the thing defined. Now, not every individual substance of rational nature is a person. For the divine essence as an essence is not a person, or else in God there would be one person just as there is one essence. Therefore, the aforesaid definition of person is unsuitable.

Obj. 13: The human nature in Christ is an individual substance of rational nature, for it is neither an accident nor a universal substance nor is it of irrational nature; and yet in Christ it is not a person, since it would follow that the divine person in assuming human nature assumed a human person. Thus, there would be two persons in Christ, the divine person assuming and the human person assumed, which is the heresy of Nestorius. Therefore, not every individual substance of rational nature is a person.

Obj. 14: The soul separated by death from the body is not said to be a person, yet it is an individual substance of rational nature. Therefore, this is not a suitable definition of person.

I answer that, as explained above, it is reasonable that the individual in the genus of substance should have a special name, because a substance is individualized by its proper principles and not by something extraneous, as an accident is by its subject. Again, it is reasonable that among individual substances also the individual of rational nature should have a special name, because (as stated above) it belongs to it properly and truly to act through itself.

Therefore, just as the word “hypostasis” according to the Greeks or “first substance” according to the Latins is the special name of an individual in the genus of substance, even so the word “person” is the special name of an individual of rational nature, so that person is a special name under both these heads.

Hence, to indicate that it is in a special manner an individual in the genus of substance, it is stated that it is “an individual substance”; and to indicate that it is in a special manner an individual of rational nature, it is added, “of rational nature.” Accordingly, by describing it as a substance, we exclude accidents from the account of person, for no accident can be a person, and by adding “individual,” we exclude genera and species in the genus of substance, since they cannot be called persons; and by adding “of rational nature,” we exclude inanimate bodies, plants, and beasts, which are not persons.

Reply Obj. 1: Three points are to be noted in an individual substance; first, the generic and specific nature existing in the individual; second, such a nature’s mode of existence, inasmuch as the generic and specific nature in the individual substance exists as proper to that individual and not as common to many; third, the principle whence is caused this mode of existence. Now, just as a nature considered in itself is common, so too is that nature’s mode of existence, for we do not find human nature existing in things except as individualized in this or that man; for there is no man that is not a particular man, except in the opinion of Plato, who posited separate universals. But the principle of that mode of existence, namely, the principle of individuation, is not common but differs in each individual, for this particular thing is individualized by this matter and that one by that matter. Accordingly, just as the term denoting the nature is common and definable, like man or animal, so too is the term denoting the nature together with such a mode of existence, for example, hypostasis or person. On the other hand, the term that includes in its signification a determinate principle of individuation is neither common nor definable, like Socrates or Plato.

Reply Obj. 2: Not only is the intention of singularity common to all individual substances, but also the generic nature together with that particular mode of existence. In this way, the term “hypostasis” denotes a nature of the genus of substance as individuated, while the term “person” denotes only a rational nature with that particular mode of existence. For this reason neither “hypostasis” nor “person” is a term of intention, like “singular” and “individual,” but denotes a real thing only, and not a real thing together with an intention.

Reply to Obj. 3–4: This suffices for the replies to the third and fourth objections.

Reply Obj. 5: While the essential differences of things are often unknown and unnamed, we are sometimes under the necessity of employing accidental differences to denote substantial distinctions, as the Philosopher teaches. (Aristotle, Metaphysics 8.2, 1043a2–28.) Thus it is that “individual” is included in the definition of person, in order to indicate an individual mode of existence.

Reply Obj. 6: The division of “substance” into first and second is not a division into genus and species, since second substance covers nothing that is not covered by first substance; rather, it is a division of a genus according to different modes of existence. Thus, “second substance” denotes the generic nature in itself absolutely, while “first substance” signifies that nature as individually subsistent; therefore, the division is analogous rather than specific. Accordingly, person is contained in the genus substance, although not as a species, but as defining a specific mode of existence.

Reply Obj. 7: Some hold that substance is included in the definition of person inasmuch as substance signifies a hypostasis; but since the account of hypostasis includes “individual” insofar as it is opposed to the community of a universal or to a part—for no universal nor any part of a thing, such as a hand or a foot, can be called a “hypostasis”—they say that “individual” is added in the definition of person inasmuch as “individual” excludes a community of assumability. For they hold that the human nature in Christ is a hypostasis but not a person. Therefore, they say to exclude assumability, “individual” is added in the definition of person.

This, however, would seem contrary to the intention of Boethius in On the Two Natures, who by the term “individual” excludes universals from the account of person. (Boethius, On the Person and the Two Natures 3 (PL 64:1343).) Hence, it is better to say that, in the definition of person, “substance” does not stand for “hypostasis” but for that which is common to first substance (that is, hypostasis) and second substance, and is divided into both. Thus, this common substance, by the addition of “individual,” is narrowed down to the hypostasis, and thus to say “individual substance of rational nature” is the same as to say “hypostasis of rational nature.”

Reply Obj. 8: In view of what we have just said, this argument does not prove. “Substance” does not stand for “hypostasis” but for that which is common to all substance in whatever sense it be taken. If, however, “substance” were to stand for “hypostasis,” the objection would remain inconclusive, because the substance that is a hypostasis is more akin to a person than is subsistence, since nonetheless “person” signifies some subject, as first substance does, and not merely as subsisting, as a subsistence. But seeing that the term “substance” is employed even by the Latins to denote the essence, therefore in order to avoid error, we do not speak of three substances, as we do of three subsistences. The Greeks, however, who have the word hypostasis as distinct from ousia (οὐσία), do not hesitate to acknowledge three hypostases in God.

Reply Obj. 9: Just as we speak of three persons in God, so may we speak of three individual substances, yet of only one substance that is the essence.

Reply Obj. 10: Rational is the difference of animal, inasmuch as “reason,” whence it is taken, denotes discursive knowledge, the sort that is found in man but not in angels nor in God. But Boethius takes “rational” in a broad sense for “intellectual,” and this is common to man, angels, and God.

Reply Obj. 11: In the definition of person, “nature” is not to be taken as the principle of movement, in which sense it is defined by the Philosopher, (Aristotle, Physics 2.1, 192b20.) but as defined by Boethius as the specific difference giving each thing its form. (Boethius, On the Person and the Two Natures 1 (PL 64:1342).) And since the difference completes the definition and confines the thing defined to its species, it follows that the term “nature” is more suitable in the definition of person, which is specific to certain substances, than is the term “essence,” which is most common.

Reply Obj. 12: In the definition of person, “individual” signifies that which is not predicated of several; and in this sense, the divine essence is not an individual substance by predication, inasmuch as it is predicated of several persons, although it is individual in itself. However, Richard of St. Victor amends the definition of Boethius as applied to the divine persons and says that a person is an incommunicable existence of divine nature, so as to indicate by the term “incommunicable” that the divine essence is not a person. (Richard of St. Victor, On the Trinity 4.18, 4.23 (PL 196:941, 945–46).)

Reply Obj. 13: Seeing that an individual substance is something complete existing through itself, the human nature in Christ, inasmuch as it was assumed into the divine person, cannot be called an individual substance, which is a hypostasis, any more than can a hand, a foot, or anything that does not subsist by itself apart from anything else; and for this reason, it does not follow that it is a person.

Reply Obj. 14: The separated soul is a part of rational nature and not a whole rational human nature; wherefore, it is not a person.