The History of Tantra
Tantra emerged early in the post-classical period, around the fourth century c.e., but didn't reach its full flowering until 500 to 600 years later. This school represents a rather radical departure for yoga philosophy. In what could only have been understood as heresy, tantra rejected the Vedas (the most sacred texts of Hinduism since at least 1500 B.C.E.) as irrelevant. It refuted the notion that liberation could be attained only through rigorous asceticism and meditation, and it dismissed the Samkhyan precept that a yogi must renounce the world in order to free himself from it. Tantra also eschewed karma yoga (the path of action or service), choosing instead to focus on devotion (bhakti), most particularly worship of the Goddess.
In teaching about the causes of suffering and the path to liberation, tantra shares common ground with its ancestors. Like the nondualistic authors of the early Upanishads, tantric yogis believed that human suffering comes from the illusion of opposites, from the mistaken notion that the Self is somehow separate from the objects it desires. Being good nondualists, tantrikas (tantric yogis) see all possible sets of opposites, all dualities (good and evil, hot and cold, hard and soft, male and female) contained within the universal consciousness. The only way a yogi can liberate himself from suffering, according to tantra, is to unite all the opposites or dualities in his own body. Like Patanjali, tantrikas believe in the need to have a strong, pure physical body.
While Patanjali may have acknowledged the need to strengthen and purify the body, he ultimately believed that the body was defiled and that a truly liberated yogi would shun the company of others for fear of becoming contaminated. Tantrika, on the other hand, celebrated the physical body, which they considered to be a sacred temple of the Divine, as a means to conquer death. The body became the vehicle for attaining liberation. In tantric yoga, the universal consciousness, which earlier philosophers called purusha, became Shiva and resided within the body. The principle of nature or creation, called prakriti in earlier yogic thought, became shakti and lived at the base of the spine. The ultimate unity—the male energy of Shiva with the feminine principle shakti—took place internally and led to final liberation or samadhi. Unlike the more traditional nondualists, however, tantrikas believed that the whole world was not an illusion, but a manifestation of the Divine and that all experience brought the practitioner closer to his or her own divinity.