 More fundamental in view of the focus of epistemological works is the distinction between reliable and non-reliable cognitions. There is agreement as to which cognitions are reliable cognitions—precisely those prescribed by Dharmakīrti, namely, perception and inference—although not as to what defines them as reliable cognitions. As for non-reliable cognitions, one finds an opposition between a fivefold typology, which is the trademark of works of the pre-classical period, and a more basic threefold typology prescribed by Sakya Pandita.