This book is about knowledge and its value. The central hypothesis is that humans think and speak of knowing in order to identify reliable informants, which is vital for human survival, cooperation, and flourishing. This simple idea is used to answer an array of complex and consequential philosophical questions. This is an excellent work. Michael Hannon very helpfully and sensitively unpacks the function-first methodology, including what Edward Craig has said on the matter. This is not, however, a re-hashing of Craig's views: Hannon develops his ideas in philosophically independent ways. Chapters individually and cumulatively are very impressive, covering a wide range of topics. They do not neglect any significant position, and respond to a truly impressive sample of contributors. Hannon is a clear and powerful thinker. I recommend this book highly.