Eastern and Western Conceptions of the Trinity: Relative Identity and Triunity

The western church affirms that each person of the Trinity is God; the West also professes that the Father is not the Son or that the Son is not the person of the Holy Spirit. Neither person of the Trinity is hypostatically identical with the other. Moreover, western theologians generally contend that the Father, Son and Holy Spirit are identical in terms of what they are whereas the tres personae are distinguished in terms of who they are. That is, their identity is thought to be substantial (metaphysical) but not hypostatical.

Yet how do these concepts overcome the problem that seems to be raised by Leibniz's Law, namely, if an entity/object X has all properties in common with an entity/object Y, then X and Y are absolutely identical? This is one formulation of Leibniz's Law, but one western answer to this apparent difficulty is relative identity wherein the Father and Son are said to be the same F (the same God) without being the same G (the same person) just like Peter and John are both human without being the same persons. But two replies to this approach might be to question relative identity and to scrutinize divine simplicity, which has been invoked to show why God differs from Peter and John.

Finally, I might say that Lewis Ayres (in his work Nicaea and its Legacy) has argued that the so-called distinction between eastern and western Trinitarianism is greatly exaggerated. Ayres presents a more nuanced account of Augustine's Trinitarianism on pp. 364-383 of his study.