A defeater is, very broadly, a consideration that reduces or completely takes away justification from a subject’s belief about a certain proposition. According to a widely endorsed view, justifiers and defeaters require evidential support. However, a number of philosophers argue that unjustified beliefs can serve as defeaters as well. Call the former type of defeater an ‘evidential defeater’ and the latter a ‘doxastic defeater’. Doxastic defeaters are highly controversial. First of all, they seem to be flatly incompatible with evidentialism. Moreover and more alarmingly, if we accept that unjustified beliefs can be defeaters, we have to accept that unjustified beliefs can serve as justifiers as well. A further unwelcome implication is that epistemically irresponsible subjects could immunise themselves from defeat by generating their own defeater-defeaters. Problems like these have led philosophers to reject doxastic defeaters altogether. This paper argues that doxastic defeaters are intelligible given a dualistic conception of rationality.
