Though I have often had occasion to touch upon the subjects treated in this book, it is yet doubtful if I should have written this work without important request behind. In the his torical references, I have had to excise portions — particularly in the Mediaeval period — of what I had written, with a view to making the work more suitable for readers in a generation that does not reckon patience among its greatest virtues. Primarily prepared for philosophical readers, those parts of the book which relate to subjects like the First Cause and the World Ground will not fail to interest theological readers also. An extended study of the litera ture of the subjects dealt with convinced me that there was ample need and room for such.