Two weeks ago Edouard Machery argued against the idea that common sense is a good guide to reality. Common sense relies on intuition; and intuitions are unreliable, vary greatly across cultures and are sensitive to seemingly irrelevant factors such as the wording of a particular thought experiment. This week Nevin Climenhaga challenges this view, arguing that we can have good intuitions and bad ones, and that there are legitimate ways of sorting reliable from unreliable ones.

Analytic philosophers frequently appeal to intuitions as evidence for philosophical claims. For example, it seems to me that knowledge can be extended by deduction and inference: if Alice knows that Bob is 25, Alice can deduce, and in so doing come to know, that Bob is over 21. On the basis of this felt intuition, I conclude that knowledge can always be extended by deduction: if you know Q and know that Q entails R, then you’re able to come to know R by deducing it from Q.