Brahman
Supreme reality is described in many schools as the ultimate foundation of being.
What it is: Brahman is, in many Hindu traditions, the supreme, absolute reality or ultimate foundation of the universe.
How the tradition understands it: It can be described as impersonal, personal, with attributes, without attributes, or transcendent to usual categories, depending on the school. It is especially central in Vedanta.
Textual basis and context: The Upanishads are the most important classical source for this concept. Later philosophical commentaries gave it very different interpretations.
Debates and variations: Advaita, Vishishtadvaita, and Dvaita, for example, diverge deeply on the nature of Brahman and its relation to the world and the self.
Supportive
Brahma Sutra 1.1.2
A classical sutra on the origin of the universe from the Absolute.
Reference: Brahma Sutra 1.1.2.
Content: The sutra deals with the reality from which the world proceeds.
Use in debate: It is central to Vedanta discussions about Brahman.
Taittiriya Upanishad 2.1
A passage on Brahman as ultimate reality.
Reference: Taittiriya Upanishad 2.1.
Content: The text describes Brahman in language of fundamental reality and the origin of being.
Use in debate: It is an important reference for Hindu metaphysics.