Descriptions of human behavior should be extensible and reducible. Why? In Prometheus Rising, Robert Anton Wilson explains Timothy Leary's theory of personality types, the "interpersonal grid", the diagrammatic representation of which consists of a circle divided by the two dimensions of friendly/hostile and strong/weak, into four quadrants (friendly strength, hostile strength, friendly weakness, and hostile weakness), with each quadrant containing sixteen subquadrants. Wilson begins by explaining that each person is born with a genetic predisposition for one of these four personality types, and after explaining them briefly reminds his readers:


  Remember again that all these categories are for convenience and
  that nature has not employed the sharp boundaries that we use in our
  models of nature. Thus, with Leary's 1957 schemata, we can further
  sub-divide our 4 types into 16 types with 4 degrees of each, for a
  total of 64 sub-types.
  
  In the next section, to simplify what may be growing too complex, we
  will reduce everything again just to the interactions of the first two
  cirtuits.
  
  Any system for decribing human behavior should be flexible enough to be extended indefinitely, and should also still contain meaning when
  reduced back to its fundamentals. (p. 81, bold emphasis added)


Leary's system fulfills these criteria because the grid, which categorizes personalities, can be extended by subdividing cells or simplified by merging cells. But to me, the criteria make no sense, since I think that every description could be extended or reduced.

Is there an example of a description of human behavior that does not fulfill the criteria of extensibility and reducability?
I would say that in the present context Wilson does not use his ad-hoc criteria to differentiate two types of models of human personality – those that fulfill his criteria, and those that don't –, but that this is a pseudo-argument, legitimizing his momentary disregard of the model's complexity and allowing him to focus on only the four basic dimensions in his argumentation.

I call the criteria "ad-hoc", because he appears to make them up on the spot and not motivate them in any way. In my opinion, the whole book is filled with this kind of normative setting of dogmata.