In this little book I have endeavoured to maintain the simplicity which is the ideal of this series.

It is more difficult, however, to be simple in a topic which, even in its illustrations, demands of the reader more or less facility in the exploration of his own mind.

I am persuaded that the attempt to make the matter of psychology more elementary than is here done, would only result in making it untrue and so in defeating its own object.
In preparing the book I have secured the right and welcomed the opportunity to include certain more popular passages from earlier books and articles.

It is necessary to say this, for some people are loath to see a man repeat himself.

When one has once said a thing, however, about as well as he can say it, there is no good reason that he should be forced into the pretence of saying something different simply to avoid using the same form of words a second time.