Gregory Nyssa’s “Not Three Gods” letter to Bishop Ablabius

The argument which you state is something like this:— Peter, James, and John, being in one human nature, are called three men: and there is no absurdity in describing those who are united in nature, if they are more than one, by the plural number of the name derived from their nature.

If, then, in the above case, custom admits this, and no one forbids us to speak of those who are two as two, or those who are more than two as three, how is it that in the case of our statements of the mysteries of the Faith, though confessing the Three Persons, and acknowledging no difference of nature between them, we are in some sense at variance with our confession, when we say that the Godhead of the Father and of the Son and of the Holy Ghost is one, and yet forbid men to say there are three Gods?

The question is, as I said, very difficult to deal with: yet, if we should be able to find anything that may give support to the uncertainty of our mind, so that it may no longer totter and waver in this monstrous dilemma, it would be well: on the other hand, even if our reasoning be found unequal to the problem, we must keep forever, firm and unmoved, the tradition which we received by succession from the fathers, and seek from the Lord the reason which is the advocate of our faith: and if this be found by any of those endowed with grace, we must give thanks to Him who bestowed the grace; but if not, we shall none the less, on those points which have been determined, hold our faith unchangeably.