Four volumes of letters on the integral yoga, other spiritual paths, the problems of spiritual life, and related subjects.

In these letters, Sri Aurobindo explains the foundations of his integral yoga, its fundamentals, its characteristic experiences and realisations, and its method of practice. He also discusses other spiritual paths and the difficulties of spiritual life. Related subjects include the place of human relationships in yoga; sadhana through meditation, work and devotion; reason, science, religion, morality, idealism and yoga; spiritual and occult knowledge; occult forces, beings and powers; destiny, karma, rebirth and survival. Sri Aurobindo wrote most of these letters in the 1930s to disciples living in his ashram. A considerable number of them are being published for the first time.