The Prasthantrayi refers to three holy books. They are: The Upanishads, the Brahma-Sutra and the Bhagavad Gita. These three books are collectively known as the Prasthantrayi or the Prasthantrayam. They form the Scriptural Trinity of the Sanatan Dharma or the Hinduism.
The Upanishads present the cream of the Vedas. The Upanishads pronounce the Ultimate Truth. The Upanishadic philosophy puts an end to all forms of ignorance in life and leads to the realization of the self. The different systems of philosophy in India find their roots in the Upanishads.
Badarayana (Ved Vyasa) was a great scholar with exceptional erudition. He initiated the challenging task of systematizing the Vedas. He meticulously studied the vast philosophical doctrines of the Upanishads. He pioneered the efforts to simplify the Upanishadic philosophy what we know as the Vedanta.
The result of his efforts was one of the most illustrious works on the Vedanta. Badarayana’s work is known as Brahma-Sutra.
The Brahma-Sutra is also referred to as Vedanta-Sutra or Uttar-Mimamsa-Sutra.
The Bhagavad Gita is a part of the great epic, the Mahabharat.
The Mahabharat, authored by the great sage Veda Vyasa, is an epic that vividly depicts the different facets of human life. There are unsurmountable aspirations, ceaseless activities and inspiring achievements in Mahabharat. Amongst all these shine out the philosophy of the Bhagavad Gita.
The Bhagavad Gita sheds a flood of light on all questions associated with life. It proclaims the relationship between the Supreme Self and the self, the Brahman and the atman, between God and man. One finds solutions to all the problems of life in the Bhagavad Gita.
If ever a controversy arises on any philosophical issue in Hinduism, the interpretation of the Prasthantrayi is final and binding. If there is a difference in the statements of the Prasthantryi and any other book of Hinduism, the former is considered supreme.
Generally the fundamental philosophy pronounced in the Prasthantrayi is referred to as the Vedanta.