Ratnakīrti (11th century CE) was a Buddhist philosopher of the Yogacara and epistemological schools (pramanavada) who wrote on logic, philosophy of mind and epistemology. Ratnakīrti studied at Vikramashila university under Jñanasrimitra (975–1025). Ratnakīrti's "Refutation of Arguments Establishing Īśvara" (Īśvara-sādhana-dūṣaṇa) argued against the Hindu concept of a creator God. Ratnakīrti also wrote the "Proof of Momentariness" (Kṣānabhaṅgasiddhi), where he defended the theory of momentariness, the view that dharmas last only for a moment.