Insufficient reasons insufficient to rescue the knowledge norm of practical reasoning: towards a certainty norm

A certain number of philosophers are attracted to the idea that knowledge is the epistemic norm of practical reasoning in the sense that it is epistemically appropriate to rely on p in one’s practical reasoning if and only if one knows that p. A well-known objection to the sufficiency direction of that claim is that there are cases in which a subject supposedly knows that p and yet should not rely on p. In light of the distinction between sufficient and insufficient reasons, some philosophers contend that these cases are inconclusive. In this paper, I argue that this insufficient reason manoeuvre is defective because it either misconstrues the relevant cases or is at odds with strong intuitions about how we (should) reason. I then put forward further considerations relative to the instability of some pieces of reasoning and show how they can be explained by a certainty norm for practical reasoning.