  Study of the nature, content and causes of cognition (buddhi, jñāna, upalabdhi) lies at the very centre of the Nyāya philosophical method. In epistemology, the question asked is: how do we distinguish between true and false cognitions, and under what conditions does a true cognition arise? In logical theory, the issue is: when does one cognition ‘follow’ from another, in some suitably articulated sense. In philosophy of language, the assumption is that sentence structure mirrors cognitive structure, and hence that an inquiry into sentence meaning proceeds via an analysis of the cognitions sentences ‘express’. The importance of this topic is reflected by The Manual of Reason, for although ‘cognition’ is technically just one of twenty-four types of quality in the Vaiśeṣika schema, its analysis accounts for nearly half of the book (TS 34–74).