a selection from the PREFACE: 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...