9

Logic II 9

The use of legs is clear to us, having them ourselves. But if we
pass the animal kingdom in review, we see that in the majority
of branches there are no such organs of locomotion; while
in the others they are present throughout some whole classes.
and are absent throughout others; That is and in still others are sometimes
present, sometimes absent. With such a distribution, begs this mode
of locomotion may be so connected with the possibility of a
form, that it would the animals of the same order could not
differ in respect to using legs; but it is evident tht animals
having legs do not form a natural group; for they are not
separated from all others in any other important particular. We thus
get a tolerably clear idea of what a natural class is: it will
amply suffice for our present purpose; though we can hardly hope
that it will turn out to be logically accurate. We also see that, when
an object has been made with a purpose, as is, of
course, the case with the sciences, no classes can be
more fundamental nor broader than those which are