The requirements of cognition determine the objective criteria of conceptualization. They can be summed up best in the form of an epistemological “razor”: concepts are not to be multiplied beyond necessity—the corollary of which is: nor are they to be integrated in disregard of necessity.
The requirements of cognition forbid the arbitrary grouping of existents, both in regard to isolation and to integration. They forbid the random coining of special concepts to designate any and every group of existents with any possible combination of characteristics. For example, there is no concept to designate “Beautiful blondes with blue eyes, 5’5” tall and 24 years old.” Such entities or groupings are identified descriptively. If such a special concept existed, it would lead to senseless duplication of cognitive effort (and to conceptual chaos): everything of significance discovered about that group would apply to all other young women as well. There would be no cognitive justification for such a concept—unless some essential characteristic were discovered, distinguishing such blondes from all other women and requiring special study, in which case a special concept would become necessary. . . .
In the process of determining conceptual classification, neither the essential similarities nor the essential differences among existents may be ignored, evaded or omitted once they have been observed. Just as the requirements of cognition forbid the arbitrary subdivision of concepts, so they forbid the arbitrary integration of concepts into a wider concept by means of obliterating their essential differences—which is an error (or falsification) proceeding from definitions by non-essentials. (This is the method involved in the obliteration of valid concepts by means of “anti-concepts.”)