Wouter Kusters argues that madness has much to offer philosophy, as does philosophy to madness. In this paper, i support both claims by drawing on a mad phenomenon which I label Radical Psychotic Doubt, or RPD. First, although skepticism is a minority position in epistemology, it has been claimed that anti-skeptical arguments remain unsatisfying. I argue that this complaint can be clarified and strengthened by showing that anti-skeptical arguments are irrelevant to RPD sufferers. Second, there's a debate about whether so-called (...) hinge commitments are beliefs or not. I argue that RPD can be used to strengthen the case that they are. Moreover, if hinges are beliefs, some madpeople are more epistemically rational than some sane philosophers. Third, drawing on my own mad experiences, I challenge evidentialism by presenting a better candidate for a truly forced cchoice about what to believe than William James' traditional religious example. I further show that in certain psychiatric contexts, evidentialism has more radical implications than Jamesian pragmatism, which comes out as more conservative. Finally, I discuss how philosophical theories like pragmatism and Pyrrhonism can provide inspiration for new and much-needed coping strategies for RPD sufferers. (shrink)