It may therefore be said to them: If matters are as you maintain, then the Messiah would be two Messiahs and two sons—one Messiah who is a god and the son of a god, and another who is a man and the son of a man; for Mary must either have given birth to the Messiah or not.
If she did give birth to him, that birth must have been either spiritual or physical. If it was physical, he would be other than the one begotten by the Father, and that necessarily yields two Messiahs. If it was spiritual, then the Messiah is one son, one hypostasis, one Messiah.
The proof for this is the iron blade that becomes one with fire: it is a single sword that burns, guards, cuts, and gives light. It is impossible for the burning and luminous quality to belong to the iron in and of itself apart from the fire—for iron that contains no fire does not burn. Nor can the fiery element be the cutting and defensive part, for the nature of fire is to illuminate and consume, not to cut.
Thus it is established and confirmed that the Melkite conviction is correct: the Messiah is one hypostasis. And the falsity of the Nestorian assertion—that the Messiah comprises two hypostases—stands exposed.