This book presents a unified and systematic philosophical account of human actions and their explanation, and it does it in the spirit of scientific realism. In addition, various other related topics, such as psychological concept formation and the nature of mental events and states, are dis­ cussed. This is due to the fact that the key problems in the philosophy of psychology are interconnected to a high degree. This interwovenness has affected the discussion of these problems in that often the same topic is discussed in several contexts in the book. I hope the reader does not find this too frustrating. The theory of action developed