Bhakti, a sentiment rooted in the worship of God, has been prevalent since the Vedic period and has evolved over time. The word Bhakti, derived from the root Bhaj which means to serve, includes worship, love and offering to God. There are two paths of devotion: Saguna and Nirguna, the second is the path of knowledge and the second is the path of love. Hinduism accepts both forms of God, with saints and devotees adopting their preferred forms. Philosophical discussion on Bhakti began in the Middle Ages, with scholars such as Shankaracharya attempting to consolidate Hinduism through the Vedas and Upanishads. Shankaracharya introduced monism, arguing that the soul and the world have no real significance apart from Brahman, and knowledge is the only means of purifying the mind. Ramanujacharya opposed Shankaracharya's theory and said that Brahma is omniscient, omnipotent and omnipresent. Nimbarkacharya also established dualism, saying that soul and nature are objectively real but dependent on God.