The great ideals of the past failed not by being outlived (which must mean over-lived), but by not being lived enough. Mankind has not passed through the Middle Ages. Rather mankind has retreated from the Middle Ages in reaction and rout. The Christian ideal has not been tried and found wanting. It has been found difficult and left untried.
The Christian faith from the beginning, is sacrifice the sacrifice of all freedom, all pride, all self-confidence of spirit, it is at the same time subjection, self-derision, and self-mutilation.