Daniel Dennett gets credit (or, if you will, blame -- we'll come to that) for the expression "Cartesian Theatre" as a name for a flaw in many theories of the human mind. The idea behind the phrase is this: one intuitive way to think of perception is as the recreation of an outward reality within an inner space. Think of a little version of yourself watching a movie relating events that are happening outside the walls of the theatre. The movie is produced in something like real time due to sensors on the outer walls of the same building. Of course if we do think of perception that way, we are open to the question: can the little guy who is my real self be sure that the movie is accurate? Maybe an evil demon has tampered with the processes of production? The way to solve such puzzles, according to Dennett, is to abandon the idea of the Cartesian theatre altogether. Now comes Markus Gabriel, a philosopher I've been reading lately. You may remember that I menti...