 Abelard’s arguments for rejecting (a)–(c) are sophisticated and subtle. For the claim that reason may be fruitfully applied to a particular article of faith, Abelard offers a particular case study in his own writings. The bulk of Abelard’s work on theology is devoted to his dialectical investigation of the Trinity. He elaborates an original theory of identity to address issues surrounding the Trinity, one that has wider applicability in metaphysics. The upshot of his enquiries is that belief in the Trinity is rationally justifiable since as far as reason can take us we find that the doctrine makes sense—at least, once the tools of dialectic have been properly employed.