Yoga (Sanskrit yuga, “union”), one of the six classic systems of Hindu philosophy, distinguished from the others by the marvels of bodily control and the magical powers ascribed to its advanced devotees. Yoga affirms the doctrine that through the practice of certain disciplines one may achieve liberation from the limitations of flesh, the delusions of sense, and the pitfalls of thought and thus attain union with the object of knowledge. Such union, according to the doctrine, is the only true way of knowing. For most yogi (those who practice yoga), the object of knowledge is the universal spirit Brahma. A minority of atheistic Yogi seek perfect self-knowledge instead of knowledge of God. In any case, it is knowledge and not, as is commonly supposed, feats of asceticism, clairvoyance, or the working of miracles, that is the ideal goal of all yoga practices. Indeed, yoga doctrine does not approve of painful asceticism; it insists that physical and mental training is not to be used for display but only as a means to spiritual ends.

Yoga practice forms a ladder leading to perfect knowledge. One: self-control (yama) involves truthfulness, abstinence, avoidance of theft, refusal of gifts, and not doing injury to living things. Two: religious observance (niyama) embraces austerity, poverty, contentment, purification rites, recital of the Vedic hymns, and devoted reliance on the Supreme Being. Three: postures (āsana), of which there are a great many, are regarded as basic to all the stages that follow. Four: regulation of the breath (prānāyāma) includes altering its depth and rhythm, breathing through either nostril at will, and the virtual suspension of breath. Five: restraint of the senses (prātyāhāra) means the withdrawal from external objects and the consequent turning of the mind upon itself. Six: steadying of the mind (dhārāna) narrows attention to some one part of the body, such as the navel, the tip of the nose, or the middle of the brow, and in that way renders the practitioner insensitive to outside disturbance. Seven: meditation (dhyāna) fixes the mind on the object of knowledge, especially Brahma, to the exclusion of all other thoughts. Eight: profound contemplation (samādhi) is the perfect absorption of thought in the object of knowledge, its union and identification with that object. The achievement of samādhi liberates the self from the illusions of sense and the contradictions of reason. It is thought that has gone beyond thought, reaching its goal by its own negation. It leads to an inner illumination, the ecstasy of the true knowledge of reality.