This book is an inquiry in epistemology directed at understanding the concept of knowledge. Its point of departure is that the standard philosophical project of analysing the concept of knowledge arbitrarily restricts the subject matter and is based on risky theoretical presuppositions. Craig develops an alternative approach, akin to the ‘state of nature’ method in political theory, which builds up the concept from a hypothesis about the social function of knowledge and the needs that it fulfils. Included in Craig's attempt to understand the concept is the endeavour to explain, in the light of his own theory, much that philosophers have written about knowledge, its analysis, the obstacles to its analysis, and scepticism. Moreover, the book aims to show not only why many languages have such constructions as ‘knows whether’ and ‘knows that’ but also why they have equivalents of ‘knows how to’ and ‘know’ followed by a direct object.