THIS little book is intended to help the student to study his own nature, so far as its intellectual part is concerned. If he masters the principles herein laid down, he will be in a fair way to cooperate with Nature in his own evolution, and to increase his mental stature far more rapidly than is possible while he remains ignorant of the conditions of his growth. The Introduction may offer some difficulties to the lay reader, and may perhaps be skipped by such at the first reading. It is necessary, however, as a foundation for those who would see the relation of the intellect to the other parts of their nature and to the outer world. And those who would fulfill the maxim "Know thyself" must not shrink from a little mental exertion, nor must expect mental food to drop ready-cooked from the sky into a lazily-opened mouth. If the booklet helps even a few earnest students, and clears some difficulties out of the way, its purpose will have been served.