Prasthanatrayi literally, three points of departure, refers to the three canonical texts of Hindu philosophy

Hindu philosophy

Hindu philosophy is divided into six schools of thought, or , which accept the Vedas as supreme revealed scriptures. Three other schools do not accept the Vedas as authoritative...

, especially of the Vedanta

Vedanta

Vedānta was originally a word used in Hindu philosophy as a synonym for that part of the Veda texts known also as the Upanishads. The name is a morphophonological form of Veda-anta = "Veda-end" = "the appendix to the Vedic hymns." It is also speculated that "Vedānta" means "the purpose or goal...

 schools. It consists of:

1. The Upanishads, known as Upadesha prasthana (injunctive texts), and the Śruti prasthāna (the starting point of revelation)
2. The Brahma Sutras
   Brahma Sutras
   The Brahma sūtras , also known as Vedānta Sūtras , are one of the three canonical texts of the Vedānta school of Hindu philosophy. A thorough study of Vedānta requires a close examination of these three texts, known in Sanskrit as the Prasthanatrayi, or the three starting points...
   
   , known as Nyaya prasthana or Yukti prasthana (logical text)
3. The Bhagavad Gita
   Bhagavad Gita
   The ' , also more simply known as Gita, is a 700-verse Hindu scripture that is part of the ancient Sanskrit epic, the Mahabharata, but is frequently treated as a freestanding text, and in particular, as an Upanishad in its own right, one of the several books that constitute general Vedic tradition...
   
   , known as Sadhana prasthana (practical text), and the Smriti prasthāna (the starting point of remembered tradition)

The Upanishad

Upanishad

The Upanishads are philosophical texts considered to be an early source of Hindu religion. More than 200 are known, of which the first dozen or so, the oldest and most important, are variously referred to as the principal, main or old Upanishads...

s consist of twelve or thirteen major texts, with many minor texts. The is part of the .The (also known as the ), systematise the doctrines taught in the Upanishads and the .

All the founders of the three major schools of Vedanta

Vedanta

Vedānta was originally a word used in Hindu philosophy as a synonym for that part of the Veda texts known also as the Upanishads. The name is a morphophonological form of Veda-anta = "Veda-end" = "the appendix to the Vedic hymns." It is also speculated that "Vedānta" means "the purpose or goal...

, viz, Adi Shankara

Adi Shankara

Adi Shankara Adi Shankara Adi Shankara (IAST: pronounced , (Sanskrit: , ) (788 CE - 820 CE), also known as ' and ' was an Indian philosopher from Kalady of present day Kerala who consolidated the doctrine of advaita vedānta...

, Ramanujacharya, Nimbarkacharya and Madhva

Madhvacharya

Madhvācārya was the chief proponent of Tattvavāda "Philosophy of Reality", popularly known as the Dvaita school of Hindu philosophy. It is one of the three most influential Vedānta philosophies. Madhvācārya was one of the important philosophers during the Bhakti movement. He was a pioneer in...

wrote (commentaries) on these texts.