This is an essay -- not a treatise -- on the most important of all matters of human concern. Although it has cost its author a great deal more thought and labor than will be apparent, it falls, in his estimation, far below the demands of its implacably urgent theme ... It suggests but the beginning of the beginning now being made to raise men's thinking onto a plain which may perhaps enable them to fend off or reduce some of the dangers which lurk on every hand--Pref.