Rudra's evolution from a minor Vedic deity to a supreme being is first evidenced in the "Shvetashvatara Upanishad" (400–200 BC), according to Gavin Flood. Prior to it, the Upanishadic literature is monistic, and the "Shvetashvatara" text presents the earliest seeds of theistic devotion to Rudra-Shiva. Here Rudra-Shiva is identified as the creator of the cosmos and liberator of souls from the birth-rebirth cycle. The period of 200 BC to 100 AD also marks the beginning of the Shaiva tradition focused on the worship of Shiva as evidenced in other literature of this period. Shaiva devotees and ascetics are mentioned in Patanjali's "Mahābhāṣya" (2nd-century BC) and in the "Mahabharata". Other scholars such as Robert Hume and Doris Srinivasan state that the "Shvetashvatara Upanishad" presents pluralism, pantheism, or henotheism, rather than being a text just on Shiva theism.