Ratnakīrti
Ratnakīrti (11th century CE) was an Indian Buddhist philosopher of the Yogācāra and epistemological ("pramāṇavāda") schools who wrote on logic, philosophy of mind and epistemology. Ratnakīrti studied at the Vikramaśīla monastery in modern-day Bihar. He was a pupil of Jñānaśrīmitra, and Ratnakīrti refers to Jñānaśrīmitra in his work as his "guru" with phrases such as "yad āhur guravaḥ". Ratnakīrti's work has been termed as "more concise and logical though not so poetical" compared to that of his teacher, although he does build on much of Jñānaśrīmitra's work. He was one of the last Buddhist philosophers in  India. Philosophy. Ratnakīrti's "Refutation of Other mindstreams" ("Santānāntaradūṣaṇa") argued that knowledge of external streams of consciousness (citta-santāna) is a form of inference (anumāna) and not direct perception (pratyakṣa). Ratnakīrti introduced the two truths doctrine as key to the nature of the discussion. Since inference deals with conceptual universals, the proof of the mindstreams of others, whilst empirically valid in relative truth (saṃvṛtisatya), does not hold ultimate metaphysical certainty in absolute truth (paramārthasatya). Ratnakīrti, therefore, argued for the ultimate truth of only "one mind" (ekacitta). By establishing the impossibility of external mindstreams, Ratnakīrti was also arguing for the non -dualism of Yogācāra "consciousness-only". Ratnakīrti argued that from an ultimate point of view, the distinctions between a subject and object, or the observer and the observed, all disappear. Ratnakīrti's theory states that there is no logical foundation for individuating mindstreams, and that there are no boundaries between minds from the perspective of ultimate truth. This sub-school of Yogācāra, Cittamātra (mind only), is also known as the "Citrādvaitavāda" school (non-dual mind) or "Vijñānādvaitavāda" school (non-dual consciousness). Ratnakīrti's "Refutation of Arguments Establishing Īśvara" ("Īśvarasādhanadūṣaṇa") argued against the Hindu concept of a creator God. He wrote that  it is not possible to establish Īśvara through inference as the Naiyāyikas did. Although the mindstreams of others are regarded as relatively true, they are not ultimately true.The text begins with an explanation of the Nyāya belief system, followed by a criticism of inferences which establish an intelligent creator. Ratnakīrti's "Proof of Exclusion" ("Apohasiddhi") establishes a theory of exclusion which follows Dignāga's theory of the same. It explains how thoughts and perception become understood through inference, and it is a theory of definitions and meaning-making. There are three types of exclusion described in the text. Works . Works attributed to Ratnakīrti include: The works are compiled in "Ratnakīrtinibandhāvali." Notes. 8. McAllister, Patrick. "Ratnakirti and Dharmottara on the Object of Activity." Journal of Indian Philosophy; Dordrecht Vol. 42, Iss. 2-3, (Jun 2014): 309-326.