The main character is the sage Yajanavalkya, who teaches that truth can only be found through negation of all thoughts about it, called the doctrine of "neti neti."
Sri Shankaracharya and some of his followers take Monism and Absolutism to be the central theme. The two oldest parts are the Brhadaranyaka, the "Great Forest text", and the Chandogya. The main character is the sage Yajanavalkya, who teaches that truth can only be found through negation of all thoughts about it, called the doctrine of "neti neti." Other parts of this work are the Isa, the Kena, and the Katha. The most important commentator on them is Sankara, and the teaching based on them is known as the Vedanta. FTP, identify this 108 part work, famously translated by Friedrich Max Muller, which is traditionally the end of the Vedas.
Sri Shankaracharya and some of his followers take Monism and Absolutism to be the central theme.
Upanishads