When a religious method recommends itself as scientific, it can be certain of its public in the West. Yoga fulfils this expectation. Quite apart from the charm of the new and the fascination of the half-understood, there is good cause for Yoga to have many adherents. It offers the possibility of controllable experience and thus satisfies the scientific need for facts; and, besides this, by reason of its breadth and depth, its venerable age, its doctrine and method, which include every phase of life, it promises undreamed of possibilities.
Every religious or philosophical practice means a psychological discipline, that is, a method of mental hygiene. The manifold, purely bodily procedures of Yoga also mean a physiological hygiene which is superior to ordinary gymnastics and breathing exercises inasmuch as it is not merely mechanistic and scientific, but also philosophical; in its training of the parts of the body, it unites them with the whole of the spirit, as is quite clear, for instance, in the pranayama exercises where prana is both the breath and the universal dynamics of the cosmos.
Yoga practice would be ineffectual without the concepts on which Yoga is based. It combines the bodily and the spiritual in an extraordinarily complete way.
In the East, where these ideas and practices have developed, and where for several thousand years an unbroken tradition has created the necessary spiritual foundations, Yoga is, as I can readily believe, the perfect and appropriate method of fusing body and mind together so that they form a unity which is scarcely to be questioned. This unity creates a psychological disposition which makes possible intuitions that transcend consciousness.