In the 1860's, following the revelations of geology and evolution, Matthew Arnold imagined the 'sea of Faith' as a tide: "But now I only hear its melancholy, long, withdrawing roar, retreating... down the vast edges drear, and naked shingles of the world." (Dover Beach) Now, in the 21st century that retreat, in the West, has reached the point that half the population has abandoned Christianity, the rituals and creeds of which have ceased to have meaning...