His Vishishtadvaita (qualified non-dualism) philosophy has competed with the Dvaita (theistic dualism) philosophy of Madhvāchārya, and Advaita (non-dualism) philosophy of Ādi Shankara, together the three most influential Vedantic philosophies of the 2nd millennium. Ramanuja presented the epistemic and soteriological importance of bhakti, or the devotion to a personal God (Vishnu in Ramanuja's case) as a means to spiritual liberation. His theories assert that there exists a plurality and distinction between Ātman (soul) and Brahman (metaphysical, ultimate reality), while he also affirmed that there is unity of all souls and that the individual soul has the potential to realize identity with the Brahman.