Prosopon

Prosopon (Greek, "face" or "mask") is an early word for a divine Person — the who of God — largely handed over to hypostasis because "mask" could suggest mere roles, but kept in the confession of Christ as one Person.

For Inquirers

In the ancient theatre an actor held up a painted prosopon — a "face," a mask — and became, for the length of a scene, the character it showed. So the word first meant the face a person presents to the world. When the early Christians were searching for words to speak of God as one being who is somehow three, this was one of the words they tried, using it to mean a "person": one of the three whos — the Father, the Son, and the Holy Spirit.

But there was a trap hidden in the word, and it is worth seeing why. If "person" means only the mask an actor holds up, then the Father, Son, and Spirit start to sound like three costumes a single performer puts on and takes off — one God playing three parts in turn. That is precisely what Christians do not believe. The Father, the Son, and the Spirit are three real someones, at the same time, always — not one actor's changing faces. So the Church came to lean on a sturdier word (hypostasis) for the Trinity, and let this softer one recede.

The word did keep one crucial home, though. When Christians say that Jesus is one person who is fully God and fully human, they say He is one face — one someone you could look at — and not two people crowded behind a single appearance. There the old theatre-word turned out to guard something precious: that the Lord who made the world and the man who wept at a friend's grave are not two, but one and the same him.

Overview

Prosopon (Greek πρόσωπον, literally "face" or "mask") is one of the early Greek words for a divine Person — the who of God (Father, Son, Holy Spirit), as distinct from the one ousia (the what).
It belonged to the contested fourth- and fifth-century vocabulary of the Trinitarian and Christological disputes: ousia, physis, hypostasis, prosopon.
For Trinitarian theology the Church came to prefer hypostasis, because prosopon's overtone of "mask" or outward appearance could suggest that the Three are merely roles a single God plays — the Sabellian (modalist) error.
The word survives with full force in Christology: the Council of Chalcedon confessed the two natures of Christ united in one Person (prosopon) and subsistence.

Summary

The word comes from the stage. A prosopon was the mask an actor raised to his face, and by extension the face or countenance a person turns toward others — the outward "who" one presents. It was natural, then, that as the Church hammered out how to speak of God she reached for it as one candidate for "person." It took its place among a small set of Greek words whose exact senses were fought over for three centuries: ousia (essence), physis (nature), hypostasis (subsistence), and prosopon (person/face). As one survey of those controversies puts it, the whole struggle was over "expressing in words the manner of the union" of the divine and the human in Christ, a struggle in which the same terms were used by different parties in different ways.[^ownest]

For speaking of the Trinity, however, prosopon carried a liability the sturdier hypostasis did not. Its theatrical root — the removable mask — lent itself to the very error the doctrine most needed to exclude: the idea that Father, Son, and Spirit are three masks worn in turn by a single divine actor, three appearances of one solitary God. That error has a name, Sabellianism or modalism, and it is exactly why the tradition marked prosopon as, in one summary, "an early, but less-preferred, Greek term… because it lends itself to confusion with Sabellianism."[^owfil] The Church's answer was not to redefine the word but to prefer a better one: hypostasis names a real, concrete subsistence — a someone who genuinely stands there — and so the Cappadocian formula settled on one ousia, three hypostases, guarding the truth that the Three are permanently and simultaneously distinct, never a single performer changing faces.

Christology gave the word its decisive role, and there its plain sense — one face, one someone you could look upon — did exactly the work required. When the Council of Chalcedon (451) confessed the incarnate Lord, it declared the two natures, divine and human, preserved without confusion and "united in one Person and subsistence, not separated or divided into two persons, but one and the same Son."[^chalcedon] "Person" there translates prosopon, set alongside hypostasis: Christ is one face, one subject, in whom Godhead and manhood meet. The single "who" who upholds the universe is the single "who" who thirsted on the Cross.

That confession answered a real controversy with a name and a moment behind it. In the dispute that led to the Council of Ephesus (431), Nestorius was understood to join the divine and the human in Christ so loosely that the Lord threatened to come apart into two persons — "two sons," a God and a man merely associated rather than truly one and the same. St. Cyril pressed the point that so shattered a union could not save, and his Twelve Anathemas, received at Ephesus, insisted that the Word was Himself made flesh, so that "the Holy Virgin is the Mother of God… inasmuch as in the flesh she bore the Word of God made flesh."[^ephesus] The union is real and personal, in the one hypostasis of the Word — two persons wearing a single mask could never have accomplished it.

The whole labour of the Church, behind its quiet preference for hypostasis over prosopon, was to say two things at once and lose neither: the one God is genuinely three, and the one Christ is genuinely one. A word first borrowed from the theatre, of all places, ended up marking the line between the true and the counterfeit at both.

See also Hypostasis (the sturdier word that replaced it for the Trinity), Ousia, The Trinity, Christology, Nestorianism, and Chalcedon.

Sources

[^ownest]: OrthodoxWiki, Nestorius — the fourth-to-sixth-century Christological disputes as arguments over "expressing in words… the manner of the union of the two conditions of Christ," conducted through "the semantic variables: ousia, physis, hypostasis, prosopon," which Cyril and Nestorius "used… differently.". [^owfil]: OrthodoxWiki, Filioque (terminology) — "prosopon (pl. prosopa) — (lit. 'face/mask') An early, but less-preferred, Greek term. It is less-preferred because it lends itself to confusion with Sabellianism.". [^chalcedon]: Council of Chalcedon (A.D. 451), The Definition of Faith — the two natures of Christ "being united in one Person and subsistence, not separated or divided into two persons, but one and the same Son." ("Person" renders prosopon.). [^ephesus]: Council of Ephesus (A.D. 431), The Twelve Anathemas of St. Cyril (Anathema 1) — "If anyone will not confess that the Emmanuel is very God, and that therefore the Holy Virgin is the Mother of God (Θεοτόκος), inasmuch as in the flesh she bore the Word of God made flesh… let him be anathema.".