Buddhism accepts only two "pramana" ("tshad ma") as valid means to knowledge: Pratyaksha ("mngon sum tshad ma", perception) and Anumāṇa ("rjes dpag tshad ma", inference). Rinbochay adds that Buddhism also considers scriptures as third valid "pramana", such as from Buddha and other "valid minds" and "valid persons". This third source of valid knowledge is a form of perception and inference in Buddhist thought. Valid scriptures, valid minds and valid persons are considered in Buddhism as "Avisamvadin" ("mi slu ba", incontrovertible, indisputable). Means of cognition and knowledge, other than perception and inference, are considered invalid in Buddhism.