 Whenever we have a taxonomically organized body of knowledge, we presuppose that subclasses inherit properties from their superclasses: dogs have lungs because they are mammals, and mammals have lungs. However, there can be exceptions, which can interact in complex ways as in the following example: mammals, by and large, don’t fly; since bats are mammals, in the absence of any information to the contrary, we are justified in inferring that bats do not fly. But if we learn that bats are exceptional mammals, in that they do fly, the conclusion that they don’t fly is retracted, and the conclusion that they fly is drawn instead. Things can be more complicated still, for in turn, baby bats are exceptional bats, in that they do not fly (does that make them unexceptional mammals?). Here we have potentially conflicting inferences. When we infer that Stellaluna, being a baby bat, does not fly, we are resolving all these potential conflicts based on the Specificity Principle. 