... are exactly similar notonly in appearance and character, but right down to the levelof neurological organisation and activity. According to externalism, we cannot explain the action of John’s ... position: see his The Elm and the Expert: Mentaleseand its Semantics (Cambridge, MA: MIT Press, 1994). An introduction to the philosophy of mind86seems, does not permit us to do this. (Of course, ... of many perceptual illusions. For example, whenpeople see an object lying at the bottom of a tank ofwater, it is very common for them to believe that theobject is closer to the surface than...