This book, first published in 1922, examines the science of Râja Yoga. All the orthodox systems of Indian philosophy point to one goal, the liberation of the soul through perfection – and the method to attain this is through Yoga. This book presents lectures on Yoga, delivered to a western audience view to explaining Indian philosophy; the lectures are accompanied by the Sutras (aphorisms) of Patanjali, along with an explanatory commentary.