 Analog representation fails to be differentiated because it is dense. With an ordering of types such that between any two types, there is a third, it is impossible to determine instantiation of at most one type. Not every case involving a failure of finite differentiation is a case of density. However, a traditional thermometer is such that heights of mercury that differ to any degree count as distinct syntactic types, the kinds of things that can differ semantically. Similarly, for pictures distinguished according to regions of color, for any two pictures, no matter how closely similar, one can always find a third more similar to each of them than they are to each other. Density is a feature of any system that measures continuously varying values. That is, as long as the system in question is designed so that any difference in magnitude indicates a difference in type.