 The map is a useful model of Classical representation. It consists, for example, of a set of lines of varying widths, lengths, and colors, and thereby represents the roads in and around a city. This is not because the roads have the properties of the map (the widths, lengths, and colors of the lines) but because the abstract structure given in the map (the relations among the lines) duplicates the abstract structure of the roads. At the heart of Classical thought is the principle that we know in virtue of having ideas that, in this sense, represent what we know. Of course, in contrast to the map, we do not need to know what the actual features of our ideas are in virtue of which they are able to represent. (In Descartes’ scholastic terminology, we do not need to know their “formal reality”.) We need to know only the abstract structure that they share with the things they represent (the structure of what Descartes calls their “objective reality”). We do, however, have direct (introspective) access to the abstract structures of our ideas: we can “see” what representational structure they have. Further, we can alter an idea’s structure to make it a better representation of an object, as we can alter a map to improve it.