"The essence of science is that it is always willing to abandon a given idea, however fundamental it may seem to be, for a better one; the essence of theology is that it holds its truths to be eternal and immutable. To be sure, theology is always yielding a little to the progress of knowledge, and only a Holy Roller in the mountains of Tennessee would dare to preach today what the popes preached in the Thirteenth Century, but this yielding is always done grudgingly, and thus lingers a good while behind the event."