-[If a category seems to come into types, you can reify those as separate sub-categories, like bipolar I and II. The idea that there's something to the idea that bipolar I and II are "different", is s]
+Is the two-type typology of bipolar disorder a good theory? Are bipolar I and bipolar II "really" different conditions, or slightly different presentations of "the same" condition, part of a "bipolar spectrum" along with cyclothymia? In our current state of knowledge, this is debateable! But if our understanding of the etiology of bipolar disorder were to advance, and we were to find evidence that that bipolar I has a different underlying _causal structure_ from bipolar II (with decision-relevant consequences, like responding to different treatments), that would support a policy of thinking and talking about them as mostly separate things (even while they have enough in common to both be kinds of "bipolar").