Another one from the bin of “great Protestant theologians of the last century”. This one from Paul Tillich. He writes in Dynamics of Faith:
Faith is a total and centered act of the personal self, the act of unconditional, infinite, and ultimate concern. The question now arise: what is the source of this all-embracing and all-transcending concern? The word “concern” points to two sides of a relationship, the relation between the one who is concerned and his concern. In both respects we have to imagine man’s situation in itself and in his world. The reality of man’s ultimate concern reveals something about his being, namely, that he is able to transcend the flux of relative and transitory experiences of his ordinary life. Man’s experiences, feelings, thoughts are conditioned and finite. They not only come and go, but their content is of finite and conditional concern – unless they are elevated to unconditional validity. But this presupposes the general possibility of doing so; it presupposes the element of infinity in man. Man is able to understand in an immediate personal and central act the meaning of the ultimate, the unconditional, the absolute, the infinite. This alone makes faith a human potentiality.