13th century

Thomas Aquinas on the Trinity: two processions and "subsisting relations"

Min: Thomas explains the Trinity through two immanent processions – of the Word (by way of the intellect: this is generation, and the Word is the Son) and of love (by way of the will: "spiration", which is the Spirit). He locates the distinction of the three persons not in the essence but in relative opposition based on origin, so the persons are "subsisting relations"; following Boethius he defines a person as an individual substance of a rational nature, applying the term to God analogically (Summa theologiae I, qq. 27–43).