How can one think about the same thing twice without knowing that its the same thing? How can one think about nothing at all (for example Pegasus the mythical flying horse)? Is thinking about oneself special? One could mistake ones car for someone elses but it seems one could not mistake ones own headache for someone elses. Why not? R. M. Sainsbury & Michael Tye provide an entirely new theory-called originalism- which provides simple & natural solutions to these puzzles & more. Originalisms central thesis is that concepts the constituents of thoughts are to be individuated by their origin rather than epistemically or semantically. The doctrine has further valuable consequences for the nature of thought our knowledge of our own thoughts the nature of experience the epistemology of perception-based beliefs & for arguments based on conceivability. Sainsbury & Tye argue that although thought is special there is no special mystery attaching to the nature of thought. Their account of the mind considers it as part of nature as opposed to something with supernatural powers-which means that human beings have more opportunities to make mistakes than many have liked to think.