Ramanuja (c. 1037–1137) was the foremost proponent of the philosophy of Viśiṣṭādvaita or qualified non-dualism. Viśiṣṭādvaita advocated the concept of a Supreme Being with essential qualities or attributes. Viśiṣṭādvaitins argued against the Advaitin conception of Brahman as an impersonal empty oneness. They saw Brahman as an eternal oneness, but also as the source of all creation, which was omnipresent and actively involved in existence. To them the sense of subject-object perception was illusory and a sign of ignorance. However, the individual's sense of self was not a complete illusion since it was derived from the universal beingness that is Brahman. Ramanuja saw Vishnu as a personification of Brahman.
What was the philosophy of qualified dualism?