Brahma-Sutra
and the sutras of Vedanta
attributed to Badarayana;
the Bhagavad-Gita
influences the moderners
very much, but the most
intense development of the
doctrine came in the
8th century A.D.
in the teachings
of Sankaracharya,
who formulated
the non-dualistic concepts
of Advaita Vedanta.
Notes: Vedarita
In the Vedic religion, Ṛta (/ˈrɪtə/; Sanskrit ऋत ṛta ‘order, rule; truth’)is the principle of natural order which regulates and coordinates the operation of the universe and everything within it.[1] In the hymns of the Vedas, Ṛta is described as that which is ultimately responsible for the proper functioning of the natural, moral and sacrificial orders. Conceptually, it is closely allied to the injunctions and ordinances thought to uphold it, collectively referred to as Dharma.
Vedic ṛtá and its Avestan equivalent aša are both thought by some to derive from Proto-Indo-Iranian *Hr̥tás ‘truth’.(Wikipedia)