" In the ultimate depths of his being man knows nothing more surely than that his knowledge, that is, what is called knowledge in everyday parlance, is only a small island in a vast sea that has not been travelled. It is a floating island, and it might be more familiar to us than the sea, but ultimately it is borne by the sea and only because it is can we be borne by it. Hence the existentiell question for the knower is this: Which does he love more, the small island of his so-called knowledge or the sea of infinite mystery? "

― Karl Rahner , Foundations of Christian Faith: An Introduction to the Idea of Christianity