Chapter 55 — That the personal distinction is constituted through the aforesaid relations in God

Since distinction in the Godhead is by relations that are not accidental, but subsistent, and since among beings subsisting in an intellectual nature there is personal distinction, it necessarily follows that personal distinction in God is constituted by the aforesaid relations. Therefore, the Father and the Son and the Holy Spirit are three persons, and similarly three hypostases, since ‘hypostasis’ means something that is subsistent and complete.