I want to share with you some of my reading through the work of Emil Brunner (1889-1966) who was professor of theology at Zurich 1924-1953.
“In Christianity faith in the Mediator is not something optional, not something about which, in the last resort, it is possible to hold different opinions…For faith in the Mediator – in the event which took place once for all, a revealed atonement – is the Christian religion itself; it is the “main point”; it is not something alongside of the centre, it is the substance and kernel, not the husk; this is so true that we may even say: In distinction from all other forms of religion the Christian religion is faith in the one Mediator…. And there is no other possibility of being a Christian than through faith in that which took place once for all, revelation and atonement through the Mediator. It is, of course, true that there are many respectable good pious people who do not believe in the Mediator. I would say all the good I can of them, but there is one thing which I cannot and ought not to say about them: that they are Christians. For to be a Christian means precisely to trust in the Mediator.”
(Emil Brunner, The Mediator, p.40)