This volume investigates the neglected topic of mental action, and shows its importance for the metaphysics, epistemology, and phenomenology of mind. Twelve specially written essays address such questions as the following: Which phenomena should we count as mental actions -- imagining, remembering, judging, for instance? How should we explain our knowledge of our mental actions, and what light does that throw on self-knowledge in general? What contributions do mental actions make to our consciousness? What is the relationship between the voluntary and the active, in the mental sphere? What are the similarities and differences between mental and physical action, and what can we learn about each from the other?