A widespread error, in this context, holds that the wider the concept, the less
its cognitive content—on the ground that its distinguishing characteristic is
more generalized than the distinguishing characteristics of its constituent
concepts. The error lies in assuming that a concept consists of nothing but its
distinguishing characteristic. But the fact is that in the process of
abstracting from abstractions, one cannot know what is a distinguishing
characteristic unless one has observed other characteristics of the units
involved and of the existents from which they are differentiated.
Just as the concept “man” does not consist merely of “rational faculty” (if it
did, the two would be equivalent and interchangeable, which they are not), but
includes all the characteristics of “man,” with “rational faculty” serving as
the distinguishing characteristic—so, in the case of wider concepts, the
concept “animal” does not consist merely of “consciousness and locomotion,” but
subsumes all the characteristics of all the animal species, with
“consciousness and locomotion” serving as the distinguishing characteristic.