According to the Second Council of Constantinople (2 June 553) there is ‘one divinity in three hypostases or persons’. Today it is commoner to say that there are three persons in one God. No doubt these formulations come to the same thing, but what is that?

The English word ‘person’ translates the Latin persona and the Greek prosopon, expressions for the masks actors wore on the ancient stage. Since the same actor might appear in different masks, playing different roles, in the same play, the word suggests that the Persons of the Trinity, the Father, Son and Spirit, are three roles the one God plays, three appearances or aspects he presents. The word ‘hypostasis’ is a philosophical term for something that exists on its own like a living organism; so to call the Father, Son and Spirit ‘hypostases’ is to suggest that they form a kind of three-membered society. Both these suggestions are unorthodox. The first is Sabellianism, the second tritheism, and these are the Charybdis and Scylla between which the speculative theologian is supposed to steer. But is such a course possible? The use of both terms by Constantinople II rather poses the problem than solves it.