 We consider it to be a bad thing to be inconsistent. Similarly, we criticize others for failing to appreciate (at least the more obvious) logical consequences of their beliefs. In both cases there is a failure to conform one’s attitudes to logical strictures. We generally take agents who fall short of the demands of logic to be rationally defective. This suggests that logic has a normative role to play in our rational economy; it instructs us how we ought or ought not to think or reason. The notion that logic has such a normative role to play is deeply anchored in the way we traditionally think about and teach logic. To consider just two examples, Kant characterizes what he calls “pure general” logic as embodying the “absolutely necessary rules of thought without which there can be no employment whatsoever of the understanding” (A52/B76), which instruct us not “how the understanding is and thinks” but “how it ought to proceed” (Kant 1974 [1800]: 16). Similarly, Frege, in his vehement opposition to the psychologistic tendencies of his time, classifies logic, “like ethics” as a “normative science” (Frege 1897/1979: 228), one whose laws “prescribe universally how one should think if one is to think at all” (Frege 1893/1903/2009: xv). This entry is concerned with the question as to whether the tradition and the intuitions that appear to underwrite it are correct. In other words, it is concerned with the question as to whether logic has normative authority over us. And if it does, in what sense exactly it can be said to do so?