1 Many persons, in their study of the sacred dogmas, failing to distinguish between what is common in the essence or substance, and the meaning of the hypostases, arrive at the same notions, and think that it makes no difference whether οὐσία or hypostasis be spoken of. The result is that some of those who accept statements on these subjects without any enquiry, are pleased to speak of “one hypostasis,” just as they do of one “essence” or “substance;” while on the other hand those who accept three hypostases are under the idea that they are bound in accordance with this confession, to assert also, by numerical analogy, three essences or substances. Under these circumstances, lest you fall into similar error, I have composed a short treatise for you by way of memorandum. The meaning of the words, to put it shortly, is as follows:
Source: Letters (New Advent)