I sketch a way of deriving Chomsky's Principles A and B of the binding theory. I first argue that English reflexive pronouns can, like English non-reflexive pronouns, be free variables. Also like non-reflexive pronouns, when bound, reflexives must be bound by a Büring-like special binder which I call an "A-probe." I suggest that Principle A derives from a requirement that certain A-probes impose. Reflexive pronouns are the exponent of those special A-probes, and the requirement that the special A-probes impose is that their exponent (the reflexive) have the same value as their argument (the DP in the Specifier of the A-probe). This requirement is expressed as a presupposition. All other A-probes are exactly like the special one, except that they have no accompanying presupposition. This allows Principle B to be a consequence of Heim's Maximize Presupposition.