What would otherwise be a mere description, may be raised to the rank of a
real definition by the peculiar purpose which the speaker or writer has in
view. As was seen in the preceding chapter, it may, for the ends of a
particular art or science, or for the more convenient statement of an
author’s particular doctrines, be advisable to give to some general name,
without altering its denotation, a special connotation, different from its
ordinary one. When this is done, a definition of the name by means of the
attributes which make up the special connotation, though in general a mere
accidental definition or description, becomes on the particular occasion
and for the particular purpose a complete and genuine definition. This
actually occurs with respect to one of the preceding examples, “Man is a
mammiferous animal having two hands,” which is the scientific definition
of man, considered as one of the species in Cuvier’s distribution of the
animal kingdom.
In cases of this sort, though the definition is still a declaration of the
meaning which in the particular instance the name is appointed to convey,
it can not be said that to state the meaning of the word is the purpose of
the definition. The purpose is not to expound a name, but a
classification. The special meaning which Cuvier assigned to the word Man
(quite foreign to its ordinary meaning, though involving no change in the
denotation of the word), was incidental to a plan of arranging animals
into classes on a certain principle, that is, according to a certain set
of distinctions. And since the definition of Man according to the ordinary
connotation of the word, though it would have answered every other purpose
of a definition, would not have pointed out the place which the species
ought to occupy in that particular classification; he gave the word a
special connotation, that he might be able to define it by the kind of
attributes on which, for reasons of scientific convenience, he had
resolved to found his division of animated nature.