Prasthanatrayi

 Prasthanatrayi (Sanskrit: प्रस्थानत्रयी, IAST: Prasthānatrayī), literally, three sources (or axioms), refers to the three canonical texts of theology having epistemic authority, especially of the Vedanta schools. It consists of:

1. The Upanishads, known as Upadesha prasthana (injunctive texts), and the Śruti prasthāna (the starting point or axiom of revelation), especially the Principal Upanishads.
2. The Brahma Sutras, known as Sutra prasthana or Nyaya prasthana or Yukti prasthana (logical text or axiom of logic)
3. The Bhagavad Gita, known as Sadhana prasthana (practical text), and the Smriti prasthāna (the starting point or axiom of remembered tradition)

The Upanishads consist of ten, twelve or thirteen major texts, with a total of 108 texts (some scholars list ten as principal – the Mukhya Upanishads, while most consider twelve or thirteen as principal, most important Upanishads). The ten Upanishads are Īśā, Kena, Kaṭha, Praṣna, Muṇḍaka, Māṇḍūkya, Taittirīya, Aitareya, Chāndogya and Bṛhadāraṇyaka.

The Bhagavad Gītā is part of the Mahabhārata. In the Bheeshma Parva.

The Brahma Sūtras (also known as the Vedānta Sūtras), systematize the doctrines taught in the Upanishads and the Gītā.

The founders of the major schools of Vedanta, Aadi Shankara and Madhvācharya, wrote bhāṣyas (commentaries) on these texts. Rāmānujāchārya did not write any bhāṣya (commentary) on the Upanishads, but Ramanuja wrote bhāṣyas (commentaries) on Brahma Sutras and Bhagavad Gita.