Beyond “Reality Testing”: Doubt and Lived Experience in Depersonalization and Derealization Disorder

Depersonalization derealization disorder (DPD) is typically defined by two criteria.First, patients experience lasting or recurring impressions of unreality (or alienation) concerning themselves, their body, or the world around them.Second, their reality testing remains intact, which usually means they know these impressions are misleading and that they, their body, or the world are in fact real (and not alienated).In his stimulating article, Casey (2026) primarily argues that individuals with intense and constant forms of DPD neither believe nor disbelieve that their body or themselves are unreal or alien; and a fortiori, they do not know if they are real.Instead, they are in doubt about these matters.Casey also argues, more incidentally, for a certain conception, which we might call Diltheyan, of DPD, according to which:-DPD consists in a disintegration of lived experience -where lived experience is construed, as per Dilthey (1890/2010), as:-a form of immediate contact with the world and thus subverts the subject/object dichotomy.-And is affective and value-laden (not purely cognitive) -(and thus, supposedly, at odds with the way empiricist philosophers and natural sciences represent us, our experiences and the world).-And DPD accordingly results in a loss of our immediate affective contact with the world.Casey's two points (the compatibility of DPD and doubt, and the Diltheyan view of DPD) are not unconnected.According to Casey, the claim that DPD patients know that their impressions are misleading amounts to the claim that they know these impressions are merely subjective and do not correspond to objective reality, which presuppose a subjective-objective dichotomy.And this subjective-objective dichotomy is precisely what the Diltheyan conception of experience (as "lived experience") thwarts.In other words, the neglect of doubting forms of DPD and of the Diltheian conception of DPD might be both rooted in a "positivist," non-Diltheian conception of experience.