Any book, written as this one is, expressly for use in class-room instruction, must meet one question with which text-books outside the realm of philosophy are not harassed. What shall be its attitude towards philosophic principles? This is a question which may be suppressed, but cannot be avoided. The older works, indeed, were not so much troubled by it, for it is only recently that psychology has attained any independent standing. As long as psychology was largely a compound of logic, ethics, and metaphysics, the only thing possible was to serve this compound, mingled with extracts from the history of philosophy. And it must not be forgotten that such a course had one decided advantage: it made psychology a good introduction to the remaining studies of the philosophic curriculum. But at present, aside from the fact that there is already an abundance of text-books of this style, which it were idle to increase, psychology seems deserving of a treatment on its own account.
On the other hand, there are books which attempt to leave behind all purely philosophic considerations, and confine themselves to the facts of scientific psychology.