There are in the Upaniṣads two conceptions of the world, one which considers the world to be a real emanation of Brāhman, and the other which regards it as an appearance of the Absolute. But on one point there is unanimity of view, i.e. the origin of the whole world is traced to the self, and not to a material source.

“Brāhman” and “ātman” are the two words, without grasping whose meaning and significance it is impossible to understand the Upaniṣads. In certain contexts where the inquiry is into the source of the universe, the expression “ātman” is employed, and in certain others where the topic of investigation is the true self of man the term “Brāhman” is used.

The Upaniṣads make a distinction between two kinds of knowledge, the higher (parā) and the lower (a-parā).The lower knowledge consists of all the empirical sciences and arts as also of such sacred knowledge as relates to things and enjoyments that perish."Widely contrasted and different are these two,” says the Kaṭha, “nescience (avidyā) and what is known as knowledge (vidyā).

Upaniṣads by their nature are opposed to ritual. In the Brihadāraṇyaka, he who worships a divinity other than the self is described as a domestic animal of the gods. Lordship on earth may be gained by sacrificing a horse. But spiritual autonomy is to be achieved renouncing the whole universe which the Upaniṣad conceives in the image of a horse.

The Upaniṣads are called the Vedanta, as most of them constitute concluding portions of the Veda, and also their teaching represents the aim or goal of the Veda. The Sanskrit word 'anta', like the English end, may mean both “terminus” and “aim.” The later Vedāntic Schools derive their name Vedanta or Veda-anta from the fact that they claim to interpret the Upaniṣads.