The doctrine of the Trinity says that there is just one God and three distinct divine persons, each of whom is God. This would seem to imply that there are three divine persons, each a different person the other persons but the same God as the other persons. If we accept what I believe is the most popular account of identity current among logicians then we must hold that this apparent consequence is contradictory. We see this as follows (it will suffice to consider just the relation of Father and Son): logicians generally treat relativized identity expressions of the form ‘is the same A as’ (here ‘A’ stands in for a term which relativizes the identity) as being analysable in terms of absolute (or unrelativized) identity according to the following equivalence schema, (E):
(E) a is the same A as b if and only if a is identical to b and a is an A and b is an A.
The view under consideration affirms the following three sentences:
(1) The Father and the Son are persons.
(2) The Father is not the same person as the Son.
(3) The Father is the same God as the Son.