It is widely agreed among epistemologists that the verb ‘knows’ is factive and that it is therefore impossible to know what isn’t so. Yet even this view has not gone unchallenged. Allan Hazlett has argued that there are strong reasons to reject the assumption that ‘knows’ is a factive verb.
Over at Experimental Philosophy, Wesley Buckwalter has a new post in which he reports a series of experiments that look in more detail at the kinds of cases Hazlett originally introduced. The results do show that people are sometimes willing to use the verb ‘knows’ with complement clauses that express false propositions, but they also point to a surprising new explanation of people’s tendency to speak in that way.