For Aquinas, the ideal situation of justice is a situation of equality. Only when the persons acting toward each other are equal is there “justice without qualification.” For an act to be an act of justice per se , it’s necessary that the persons be “absolutely other” and “absolutely distinct,” which is to say that the persons are not defined in terms of each other.

Justice without qualification is not possible in a father-son relation, since the son is subject to the father, and the father has a kind of “ownership” in the son. A father thus can strike his son and remain just; but to strike an equal is unjust.

Aquinas would certainly see justice perfected in an absolute sense in the relations of the Trinity. The Father, Son, and Spirit can act with justice toward one another because they are absolutely equal. But they are not “absolutely other”; the Father is Father in relation to the Son, and the Spirit is who He is in relation to Father and Son. Thus, the absolute perfection of justice violates one of Aquinas’s fundamental principles of justice.

Two questions: First, is Thomas’s definition of justice a hint of a failure to press Trinitarian categories into his moral theory? Second, what does it do to Thomas’s theory of justice to introduce a more overtly Trinitarian framework? Would we have to tamper with Thomas’s basic definition of justice as rendering to each what is due?