Ramanuja is the main proponent of Vishishtadvaita philosophy. The philosophy itself is considered to have existed long before Ramanuja's time. Ramanuja continues along the line of thought of his predecessors while expounding the knowledge expressed in the Upanishads, Brahma Sutras and Bhagavad Gita. Vedanta Desika and Pillai Lokacharya, disciples in the tradition of Ramanuja, had minor disagreements not on the philosophy, but on some aspects of the theology, giving rise to the Vadakalai and Thenkalai schools of thought, as explained below.