Four Vaiṣṇava Sampradāyas and Siddhāntas—There are four Vaiṣṇava schools (sampradāyas) of Vedānta. These are 1) the Śrī Sampradāya, whose ācārya is Rāmānuja; 2) the Brahmā Sampradāya, whose ācārya is Madhva; 3) the Rudra Sampradāya, whose ācārya is Viṣṇusvāmī, and 4) the Kumāra Sampradāya, whose ācārya is Nimbārka. Opposed to these is the non-Vaiṣṇava Vedāntist school of Śaṅkarācārya. Every Vedāntist school is known for its siddhānta or essential conclusion about the relationships between God and the soul, the soul and matter, matter and matter, matter and God, and the soul and souls. Śaṅkarācārya's siddhānta is Advaita, nondifference (i.e. everything is one, therefore these five relationships are unreal). All the other siddhāntas support the reality of these relationships from various points of view. Rāmānuja's siddhānta is Viśiṣṭādvaita, qualified nondifference. Ma-dhva's siddhānta is Dvaita, difference. Viṣṇusvāmī's siddhānta is Śuddhādvaita, purified nondifference. And Nimbārka's siddhānta is Dvaita-advaita, difference-and-identity. The Bengali branch of Madhva's sampradāya is known as the Brahma-Madhva-Gauḍīya Sampradāya, or the Caitanya Sampradāya. In the 1700's this school presented Indian philosophers with a commentary on Vedānta-sūtra written by Baladeva Vidyābhūṣaṇa that argued yet another siddhānta. It is called acintya-bhedābheda-tattva, which means simultaneous inconceivable oneness and difference. In recent years this siddhānta has become known to people from all over the world due to the popularity of the books of His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda. Acintya-bhedābheda philosophy maintains the same standpoint of difference as Madhva's siddhānta on the five-fold relationship of God to soul, soul to matter, matter to matter, matter to God and soul to soul. But acintya-bhedābheda-tattva further teaches the doctrine of śakti-pariṇāma-vāda (the transformation of the Lord's śakti), in which the origin of this five-fold differentiation is traced to the Lord's play with His śakti or energy. Because the souls and matter emanate from the Lord, they are one in Him as His energy yet simultaneously distinct from Him and one another. The oneness and difference of this five-fold relationship is termed acintya or inconceivable because, as Śrīla Prabhupāda writes in his purport to Bg. 18.78, Nothing is different from the Supreme, but the Supreme is always different from everything. As the transcendental origin and coordinator of His energies, God is ever the inconceivable factor. See Advaita, Dvaita, Māyāvādī philosophy, Six systems, Vedānta, Vedānta-sūtra.