In this paper, I will argue for two interrelated theses. First, if we take phenomenological psychopathology seriously, and want to understand what it is like to undergo various psychopathological experiences, we cannot treat madpeople’s testimony as mere data for sane clinicians, philosophers, and other scholars to analyze and interpret. Madpeople must be involved with analysis an interpretation too. Second, sane clinicians and scholars must open their minds to the possibility that there may be experiences that other people have, which they nevertheless cannot conceive of.
I look at influential texts in which philosophers attempt to analyze and understand depersonalization and thought insertion. They go astray because they keep using their own powers of conceivability as a guide to what is or is not humanly possible to experience. Several experiences labelled inconceivable and therefore impossible by these philosophers, are experiences I have had myself.
Philosophers and others would be less likely to make this mistake if they would converse and collaborate more with the madpeople concerned. When this is not feasible, they should nevertheless strive to keep an open mind. Fantastical fiction may have a role to play here, by showing how bizarre experiences may nevertheless be prima facie conceivable.