Assertion and the “How do you know?” challenge

One of the central arguments for the knowledge norm of assertion appeals to the fact that it is typically legitimate to respond to an assertion with “How do you know?”, intended as a challenge to the assertion. The legitimacy of the challenge is taken as evidence in favor of the idea that permissible assertion requires knowledge. In this paper, I argue that if the legitimacy of “How do you know?” challenges supports a knowledge norm for assertion, it also supports the controversial KK thesis. I further argue that data from assertion prompts likewise supports KK. This is an unwelcome consequence for many proponents of the knowledge norm of assertion who reject KK. At the same time, it constitutes new evidence from conversational patterns in favor of the KK thesis.