(Puruṣa): The Self that abides in the heart of all things. It is the spiritual monad, which, according to the philosophy Patanjali expressed in the Yoga Sutras (the Yoga Darshana, known as Classical Yoga), is individual. Conversely, prakriti (Nature) is infinite. Even though purusha (Spirit) is seen as individual (while according to Advaita Vedanta, atman is universal, identical to Brahman), it remains the witness of all psycho-mental phenomena. In the Yoga Sutras (2:21), Patanjali says that prakriti exists only for the sake of serving purusha’s liberation.