Faith and Philosophy

published on April 14, 2015

Against the Geachian Theory of the Trinity and Incarnation

Relative-identity theories of the Trinity and Incarnation are worth another look. But not all such theories are the same. One important difference among them concerns restricted quantification. Peter Geach proposes two theses: the sortal relativity of identity and the irreducibility of restricted quantification. Every relative-identity theory of the Trinity and Incarnation applies Geach’s first thesis. But only what I call “the Geachian theory” applies both theses. I argue that any such Geachian theory faces significant theoretical disadvantages. Towards the end, I propose a closely related but non-Geachian relative-identity theory that doesn’t share those theoretical disadvantages.