In this paper I argue against John MacFarlane’s (2014) radical relativist semantics. By developing an argument of Ross & Schroeder (2013) I claim that belief in this relativist theory is incompatible with being a rational agent that acts in accordance with the norms of assertion and retraction. My conclusion is therefore that MacFarlane's semantics is committed to postulating that competent speakers are ignorant of the very theory that provides a – putative – correct account of their linguistic behaviour.
