Tibetan philosophy developed from the texts and assumptions of Indian Buddhism and almost exclusively in the Buddhist sphere, offering interesting solutions and developments to the Madhyamaka, Pramāṇavāda and, to a lesser extent, Yogācāra currents. Some key concepts used by contemporary interpreters of Indian and Buddhist philosophy, such as the distinction between a *svātantrika and a *prāsaṅgika current in Madhyamaka, and the notion of «root text» (mūla) of a certain school, dating back to Tibetan scholasticism.
In the self-representation of their own tradition, Tibetan thinkers give a decisive role to the debate held in bSam yas towards the end of the 8th century, during which it was decided what form of Buddhism to adopt in Tibet. In opposition, there were the gradualist current, of Indian origin, linked to Śāntarakṣita and Kamalaśīla (Madhyamaka) and which was the winner of the debate, and an instantaneist one, of Chinese origin and linked to Chan Buddhism. Instantaneism then remained a constant key of interpretation and was applied to various forms, always minor, of Tibetan Buddhism.
The idea that no practice was needed to achieve awakening (bodhi) was proposed to bSam yas, since Buddha’s nature is already present ab initio in everyone and it is only necessary to realize it through a form of intuitive anagnosis. On a more properly philosophical level, central to Tibetan philosophy is the debate among the supporters of «emptiness in itself» and «emptiness of what is other» (śūnyatā). Three of the four major Tibetan religious schools, the Sa skya, the bKa’ brgyud and the rNying ma, adhere to the Madhyamaka interpretation called «emptiness of what is other», which maintains that the absolute is devoid of all conceptual and dependent superimpositions, and therefore «empty» with respect to these, but not empty in itself.
Nāgarjuna’s writings – according to this interpretation – would deny any reality at the level of conventional reality (saṃvr̥ti-satya), but not at that of absolute reality (paramārtha-satya). This would consist of knowledge (in Tibetan ye shes) that goes beyond the distinction between subject and object and is identifiable with the nature of the Buddha beyond its historical manifestation. This interpretation is decisively opposed by the dGe lugs school, from whose ranks come the great thinker Tsong kha pa (1357-1419), who accused supporters of the «emptiness of what is other» of turning Buddhism into a substantialist philosophy.
Tsong kha pa, therefore, adheres to Candrakīrti and the Madhyamaka current *prāsaṅgika. However, Tsong kha pa himself opposes Pa tshab and his disciples, who, following the current *prāsaṅgika, deny any proposition of Nāgārjuna’s tetralemma claiming that everything neither «exists», nor «does not exist», nor «exists and does not exist».
This representation, according to Tsong kha pa, is self-contradictory and does not explain what is learned by the means of valid knowledge (pramāṇa). If, in fact, each object is ultimately empty and illusory, there is no distinction between the content of correct knowledge and that of an error, that is, between a vase and a piece of nacre that is mistaken for silver. In order to avoid such consequences, Tsong kha pa specifies the first two propositions of the tetralemma, which therefore states that everything neither «exists from the point of view of absolute reality» nor «does not exist from the point of view of conventional reality».
In Tibetan monastic universities the cursus studiorum is composed of epistemology (pramāṇa), Prajñāpāramitā, Madhyamaka, Vinaya, and Abhidharma (Theravāda). For epistemology, Tibetan philosophy develops its own literature, called bDus grwa, while the last five topics are studied on the basis of Indian texts, but through manuals based on the terminology of the bDus grwa. This develops discussions about vyāpti (anumāna), denial and classifications of correct or erroneous knowledge based on a Sautrāntika ontology as represented in Dharmakīrti.
Constant is the attention to produce formally correct definitions and their use in debates. Especially in its beginnings, connected to the figure of Phya pa (1109-1169), the bDus grwa elaborates areas of investigation separate from those dealt with in India, while Sa skya Paṇḍita (1182-1251), one of the most important thinkers of Tibetan philosophy, strives to bring epistemology within the mark of Dharmakīrti. Developed in Tibetan philosophy is also the theory of apoha.