 Granted, psychological categories seem to be more like biological species than like gold, magnesium or atomic particles, for instance, in possessing fuzzy boundaries and seeming to rest on continua, rather than forming discrete categorical entities. But the differences have often been seen as profound, as three examples will demonstrate. (i) Some have taken psychological categories to represent a different order of being, as we saw in  Section 5,  with its own distinctive forms of causal explanations (Jaspers 1913 [1963]; Bolton 2008; Wiggins &amp; Schwartz 2011; Kusters 2016). (ii) Others point out that psychological categories can alter, and eventually even be altered by, the persons they classify, forming “interactive” kinds through such looping effects. Indeed, mental disorders have been denied the status of natural kinds on precisely the grounds that instability in their properties results when they have been classified and labeled (Hacking 1995). And in a final example (iii), some have tried to show that the relation between mental illnesses and biological kinds differs according to the role played by values in establishing the taxa of mental illness (Wakefield 1992; this claim is discussed in  §8).  None of these differences has gone un-criticized. A thoroughgoing mind to brain reductionism would reject (i). About (ii), it has been pointed out that the classification of biological species is also subject to the instability wrought by looping effects. And similarly, it has been argued in response to (iii) both that values also enter into the classification of biological species, and that once we reach the categories of interest in this analysis, non-evaluative traits form the observable taxa of such species (Cooper 2007).