The general assumption that human knowledge depends, firstly, on our faculty to receive some raw material from the world outside us and, secondly, on our faculty to "organize' or to "structure' this material by means of certain concepts may sound quite innocent. At a close look, however, it appears to be anything but clear. In an article entitled "On the Very Idea of a Conceptual Scheme", the philosopher Donald Davidson has called this assumption "the third dogma of empiricism" (Davidson 1984, 189).