The Yoga Sutras are very short, only a few pages in the original, yet Patanjali packs into them a complete account of the inner life and how to master it. This edition is Charles Johnston's interpretation, which keeps the four-book structure of the original and adds commentary that often reaches for parallels in Christian and other mystical writing. Johnston's central claim is that the sutras describe one thing: the birth of the spiritual man out of the psychic man.
Book I sets the problem and the goal. We think we live a physical life, but in truth we have long lived a psychic one, centred in a world of mental images, memories, hopes, fears, and desires. These powers are not evil in themselves; they are spiritual powers run wild and perverted. The first sutras name the goal as union of the soul with the Oversoul, reached through control of the restless psychic activities, so that the Seer at last comes to consciousness in his own nature.
Book II turns to practice. It names the hindrances that hold a person back, unwisdom, self-assertion, lust, hate, and attachment, and shows how each is worn away by its opposite and by meditation. Then it gives the famous eight means of yoga in order: the commandments and the rules of conduct, right poise of the body, control of the life-force, withdrawal of the senses, attention, meditation, and contemplation. Johnston stresses that these steps are simple and familiar, and that the whole difficulty is in actually doing them, in their proper order.
Book III defines the inner stages of concentration. Attention is the binding of the mind to one region; meditation is holding it there; contemplation is the state in which the sense of separateness falls away and the meaning of the object shines out. The three practised together on one object form perfect concentration. From this discipline arise the powers the book is known for, but Johnston treats them as by-products and warns that clinging to them is itself a snare.
Book IV brings the argument to its close. All of nature, on this view, exists to bring forth and perfect the spiritual man, who is the crown of its long evolution. When that purpose is attained, the round of change and rebirth gives place to enduring being. Johnston ends by reconciling two ways of describing the same outcome: it can be read as the culmination of natural evolution, or as the return of pure consciousness to its own essential form.