THE human being who thrills to the experience of beauty in nature and in art does not forever rest with that experience unquestioned. The day comes when he yearns to pierce the secret of his emotion, to discover what it is, and why, that has so stung him - to defend and to justify his transport to himself and to others. He seeks a reason for the faith that is in him. And so have arisen the speculative theories of the nature of beauty, on the one hand...