These lectures are intended to give an outline of Yoga, in order to prepare the student to take up, for practical purposes, the Yoga sutras of Patanjali, the chief treatise on Yoga. I have on hand, with my friend Bhagavan Das as collaborator, a translation of these Sutras, with Vyasa's commentary, and a further commentary and elucidation written in the light of Theosophy. To prepare the student for the mastering of that more difficult task, these lectures were designed; hence the many references to Patanjali. They may, however, also serve to give to the ordinary lay reader some idea of the Science of sciences, and perhaps to allure a few towards its study.