 DSM-type classification adheres to a classical nineteenth century disease model, whereby each disease is a discretely bounded entity, made up of a symptom cluster emanating from underlying organic states or processes within the individual patient. The applicability of each aspect of this model to mental disorder has been challenged. Some would replace its idea of validity (involving a relation between classificatory name and underlying disease) with the statistical concept of predictive or prognostic validity, which proceeds without reference to underlying causes. Rather than discretely bounded, many disorders appear to be continuous with normal states. In an interpretive and definitional choice, over which the data remains ambiguous, mental disorders arguably represent no more than tails of normal distributions of particular traits in the general population (Machery 2017). But the uniformity of these normal distributions has also been questioned (Poland &amp; Tekin 2017).