The externalist conception of the mind was one of the most significant developments in the philosophy of mind in the second half of the twentieth century. Despite its central importance, however, most recent work on externalism has been very technical, often making the basic ideas and principles difficult for students to grasp. As well, comparatively little work has been done to situate externalism in the history of philosophy, in either analytic and continental traditions. Mark Rowlands remedies both these problems, presenting a clear and accessible introduction to externalism that is grounded in wider developments in the history of philosophy. Rowlands discusses Sartre's radical reversal of idealism and the Husserlian views that prompted it; Wittgenstein's attack on the assimilation of meaning and understanding to an inner process; Putnam's and Burge's thought experiments and the externalism about content to which those experiments gave rise; the scope and limits of content externalism; and the extension of externalism to consciousness.