The Upanishads are a collection of ancient Indian texts that form the philosophical underpinnings of Hinduism. They are considered to be the concluding part of the Vedas, which are the oldest sacred scriptures of Hindu tradition. Composed between 800 BCE and 200 BCE, the Upanishads marked a significant shift from ritualistic practices to spiritual and philosophical inquiry. These texts explore profound concepts such as the nature of reality, the self, and the ultimate truth, or Brahman. They delve into complex metaphysical discussions and seek to provide answers to existential questions about the meaning and purpose of life.