This book takes purism about knowledge as the default position and defends it from the challenges of pragmatic encroachment. The book is divided into two parts, a negative and a positive one. The negative part critically examines existing purist strategies in response to pragmatic encroachment. The positive part provides a new theory of how practical factors can systematically influence our confidence and explores some implications of such influence. In particular, it provides a new purist explanation of the data commonly used (...) to motivate pragmatic encroachment on knowledge. Moreover, it develops a new variety of pragmatic encroachment, not on knowledge but on credence. Thus, my aim in this book is not to provide a full-fledged defence of all kinds of purism. Rather, I argue for purism about knowledge but pragmatic encroachment about credence. This book is a revised version of my PhD dissertation “Belief, Knowledge and Action”. In this revision, I have made some substantive changes, introduced some stylistic changes and added discussions of new relevant literature. (shrink)