Yoga is one of the six Indian philosophies of the astika (orthodox) group, the others being Nyaya, Vaiseshika, Sankhya, Mimamsa and Vedanta. As the yoga philosophy has no metaphysics of its own, it accepts the teachings of Sankhya to formulate the methods to attain its goal.
The purpose of yoga practice is to release purusha (cosmic spirit) from prakruti through mind control. The subject is dealt with in depth in the Upanishads and Bhagavad Gita, the sacred texts of India. However, Patanjali’s Yoga Sutra is considered as the classical text on yoga system.