Abstract

We show that taking together the principle ‘Ought’ Implies ‘Can’ (OIC) and The Knowledge Norm of Assertion (KNA) leads to a contradiction as long as we assume that there are situations in which we ought to assert what we cannot know. We call this The Paradox of Impossible to Know Assertion (PIKA) and argue that this is a genuine problem. At the end, we point out a generalization of PIKA.