In making an attempt to estimate the philosophical ideas of the last century and a quarter, I have endeavored as a historian to be accurate, and as impartial as nature will permit a philosopher to be when dealing with opinions more or less out of harmony with his own. But it may prevent misleading anticipations if I confess at the start that the tracing of historical affiliations and historical causes has had only a secondary interest for me, and that the book as a whole is frankly propaganda, and designed to recommend one particular attitude as against competing attitudes; apart from this critical interest, it is not very likely that the work would have been carried through. If it were urged that fewer pages of criticism, and more attention to historical and descriptive data, would have resulted in a more generally useful volume, I do not know that I should be prepared to combat the claim; though I think it might be argued that one way, and at times the only way, to give an intelligible account of a philosophical doctrine, especially of the more esoteric sort, is by pointing out its limitations and obscurities. My real excuse however for writing a book in which criticism plays so large a part is that I wanted to do so.
The particular philosophical standpoint which the following pages presuppose as a background, is one which, I am regretfully aware, many philosophers, perhaps most of them, will regard as lamentably crude and unadventurous. Typically two conceptions have been predominant in the history of thought--the psychological, and the logical. For the one, reality is to be interpreted as experience, beyond which the philosopher should not attempt to pry, "experience" stand-