“Through God alone can God be known. The knowledge of God comes only through revelation. This assertion is not peculiar to the Christian Faith, it is found in all religions. The Christian faith, however, claims that only in it, that is, in the revelation of God in Jesus Christ, does this assertion attain truth and reality. No proof can be adduced in support of this belief; indeed, those who ask for proofs simply show that they do not understand the statement, for a revelation which could be proved would be no revelation. It would be based upon some general truth outside itself. But a static truth  of this kind – a general truth – would be the very opposite of revelation, and any doctrine which might be based upon it could only be called ‘revelation’ by a gross misuse of terms, and a gross misunderstanding of the real meaning of revelation.

On the other hand, however, there is one point which can be proved, and it is this: by ‘revelation’ – and therefore by the term ‘God’ – Christianity means something totally different from all forms of religion or philosophy. Further, it is also true that this sense of the uniqueness of faith is not an accretion, evolved in support of its claims, or a later theological theory, but an integral part of faith itself. A real Christian faith is impossible apart from the conviction that here, and here alone, is salvation. For the Christian faith is related to an historical event which took place once for all. The very fact that it arose in this way constitutes the revelation. This event is not merely the starting point of faith, it is also the foundation upon which it is built. It belongs to the essence of the Christian faith that it is based upon this solid foundation, that everything depends upon this fact, upon this event which took place once for all.”

(Emil Brunner, The Mediator, p.201)