to make clear that he means just what we mean by two persons, two Christs—namely, Jesus Son of Mary, and the Word of God who dwelt in him.
The philosophical terms certainly need explanation; our judgement as to their correctness will depend on how the people who use them do explain them. Those which occur in this controversy are: οὐσία, φύσις, ὑπόστασις, πρόσωπον. In our later scholastic use these are simple enough. οὐσία is essence, φύσις is nature, ὑπόστασις or πρόσωπον mean person. Therefore, in our Lord we see two natures (or essences)[1]—that is, two οὐσίαι, two φύσεις,[2] but one person (one ὑπόστασις, one πρόσωπον). In the 5th century it was not quite so clear. Οὐσία and φύσις meant the same thing, normally "essence" or "nature." Yet St. Cyril makes the phrase "one incarnate nature (μία φύσις σεσαρκωμένη) of the Word of God" his axiom. Was he, then, a Monophysite? No, because the Word of God has one nature proper to himself, one infinite divine nature. And that nature is incarnate, σεσαρκωμένη, made flesh, itself undestroyed—as we should say, assumes a human nature. St. Cyril means what we mean. Then, does hypostasis necessarily mean person? By no means. The Latin persona originally meant an actor's mask;[3] then the part you play in a drama, as we say "dramatis personæ"; then the part you play in life, the responsible individual who eats, drinks, studies, marries and dies. When there is a collective individuality we talk about a "persona moralis," as in the case of a corporation. The exact Greek equivalent of this is not ὑπόστασις but πρόσωπον.[4] Φύσις (nature) and πρόσωπον (person), then, are fairly clear. Hypostasis is one of those words which lie between two others and may be understood of either. Etymologically it is nearer to φύσις. Ὑπόστασις exactly equals the Latin substantia, and substance (in scholastic use) is nature. Suppose, then, that a man or a school of philosophy uses φύσις of nature in general, of what we should call the "universal," the abstract idea of humanity or
