Prana

The Upanishads already treat prana as prior to the other senses: the Prashna Upanishad and Chandogya Upanishad both tell a fable in which speech, sight, hearing and mind each claim to be the greatest of the body's powers, and each in turn withers when prana departs, proving that prana alone sustains the rest. Prana is one word doing several jobs in these texts: the breath itself, the general life force, and also the name of one particular current among five, the pancha vayu, that moves outward through the mouth and nostrils. The other four, apana (downward, elimination), samana (digestive, centering), udana (upward, speech and growth) and vyana (pervading, circulation), divide the body's work between them, a scheme set out fully in Ayurvedic and later Hatha Yoga sources.

Pranayama, restraint of the breath, is the fourth limb of Patanjali's eight-limbed yoga in the Yoga Sutras, and Hatha Yoga texts such as the Hatha Yoga Pradipika treat it as the direct technology for gathering prana and driving it up the central channel, sushumna nadi, through the network of seventy-two thousand nadis the body is said to contain. Where prana is forced into sushumna in sufficient concentration, it is said to rouse kundalini, the dormant coiled energy at the base of the spine, and drive it upward through the chakras. Prana is described as continuous with the universal life force, Brahman acting in the body, so that cultivating it is simultaneously a physiological and a soteriological act, not two separate things.

Prana entered Western vocabulary largely through the same channel as kundalini and the chakras: late nineteenth and early twentieth century popularizers, chief among them Swami Vivekananda, who lectured on Raja Yoga in the United States and Europe in the 1890s and rendered prana in English as "vital force" or "life energy," terms with no exact Sanskrit equivalent that nonetheless stuck. Theosophical writers absorbed and reworked the concept alongside their own etheric vocabulary, often blurring the line between the Sanskrit source and their own additions, a pattern scholars of modern yoga such as Mark Singleton have traced in detail; the postural yoga most familiar in the West today is itself a twentieth century synthesis, not a straightforward transmission of the older textual tradition.

Prana has also long been rendered, especially by early translators, as "breath" outright, which flattens the distinction the sources themselves draw between ordinary respiration and the subtler force breath merely carries. It has never been the subject of a controlled scientific test in the way animal magnetism or the odic force were: as a concept internal to a living religious and medical tradition it is described in its own terms here, not adjudicated.