Vaishnavism in the 8th century came into contact with the Advaita doctrine of Adi Shankara. Vasudeva has been interpreted by Adi Shankara, using the earlier Vishnu Purana as a support, as meaning the supreme self or Vishnu, dwelling everywhere and in all things, although many other schools of Hindu philosophy have a different interpretation of this key concept. There were counter-movements in South India to Shankara's theory of Brahman in particular, Ramanuja in the 11th century and Madhva in the 13th, building on the devotional tradition of the Alvars (Shri Vaishnavas).