5.1.5 Normativity in Logic

What if Lulu claims that she is 5 feet tall and that she is 7 feet tall? You’d think that she was joking or not being literal because this is tantamount to saying that she is both 5 feet tall and not 5 feet tall (which is implied by being 7 feet tall). The statement “I’m 5 feet tall and not 5 feet tall” is a contradiction. Surely Lulu does not believe a contradiction. We might even think, as Aristotle did, that it is impossible to believe a contradiction. But even if Lulu could believe a contradiction, we think that she should not. Since we generally believe that inconsistency in reasoning is something that ought to be avoided, we can say that logic is normative. Normativity is the assumption that certain actions, beliefs, or other mental states are good and ought to be pursued or realized. Normativity implies a standard (a norm) to which we ought to conform. Ethics is a normative discipline because it is the study of how we ought to act. And because we believe people ought to be logical rather than illogical, we label logic as normative.

While ethics is normative in the realm of actions and behavior, logic is normative in the realm of reasoning. Some rules of thought, like the law of noncontradiction, seem to be imperative (a command), so logic is a command of reasoning. Some philosophers argue that logic is what makes reasoning possible (MacFarlane 2002). In their view, logic is a constitutive norm of reasoning—that is, logic constitutes what reasoning is. Without norms of logic, there would be no reasoning. This view is intuitively plausible: What if your thoughts proceeded one after the other, with no connection (or ability to detect a connection) between them? Without logic, you would be unable to even categorize thoughts or reliably attach concepts to the contents of thoughts. Let’s take a closer look at how philosophers use special logical statements to organize their reasoning.