The Upanishads (Devanagari: उपनिषद्, Upaniṣad; also known as Vedānta and Śrutiśira) are part of the Vedas and form the Hindu scriptures which primarily discuss philosophy, meditation and nature of God; they form the core spiritual thought of Vedantic Hinduism. The Upanishads are mystic or spiritual contemplations of the Vedas, their putative end and essence, and thus known as Vedānta ("the end of the Vedas"). The Upanishads were composed over several centuries. The oldest, such as the Brhadaranyaka and Chandogya Upanisads, have been dated to around the eighth century BCE. The roots of many Indian religions are built upon the foundation of the Upanishads.