When one gives up the Christian faith, one pulls the right to Christian morality out from under one's feet. This morality is by no means self-evident. Christianity is a system, a whole view of things thought out together. By breaking one main concept out of it, the faith in God, one breaks the whole. It stands or falls with faith in God.

The portable Nietzsche: selected and translated, with an introd., pref. and notes (ed. Viking Pr, 1968)