THIS book was planned many years ago. As to the idea running through it, I cannot say when that arose. My feeling is, it was born with me. On reflection, indeed, it seems possible the seeds fell imperceptibly in youth--from F. A. Lange, maybe, and other sources--to germinate unseen in a congenial soil. However that may be, the idea underlies much that I have written. Even the present book began to be written, and to be published in a preliminary form, more than fifteen years ago. Perhaps I may be allowed to seek consolation for my slowness, however vainly, in the saying of Rodin that "slowness is beauty," and certainly it is the slowest dances that have been to me most beautiful to see, while, in the dance of life, the achievement of a civilisation in beauty seems to be inversely to the rapidity of its pace.