sh agriculture are distinguished, in settling their
rotation, into white and green; the botanist divides the higher plants
into gymnosperms and angiosperms, and the latter into monocotyledons and
dicotyledons. The principle of resemblance and difference is recognised
in all these cases; but what resemblances or differences are important
depends upon the purpose to be served.

Purposes are either ([alpha]) special or practical, as in gardening or
hunting, or ([beta]) general or scientific, as in Botany or Zoology. The
scientific purpose is merely knowledge; it may indeed subserve all
particular or practical ends, but has no other end than knowledge
directly in view. And whilst, even for knowledge, different
classifications may be suitable for different lines of inquiry, in
Botany and Zoology the Morphological Classification is that which gives
the most general and comprehensive knowledge (see Huxley, _On the
Classification of Animals_, ch. 1). Most of what a logician says about
classification is applicable to the practical kind; but the scientific
(often called 'Natural Classification'), as the most thorough and
comprehensive, is what he keeps most constantly before him.

Scientific classification comes late in human history, and at first
works over earlier classifications which have been made by the growth of
intelligence, of language, and of the practical arts. Even in the
distinctions recognised by animals, may be traced the grounds of
classification: a cat does not confound a dog with one of its own
species, nor water with milk, nor cabbage with fish. But it is in the
development of language that the progress of instinctive classification
may best be seen. The use of general names implies the recognition of
classes of things corresponding to them, which form their denotation,
and whose resembling qualities, so far as recognised, form their
connotation; and such names are of many degrees of generality. The use
of abstract names shows that the objects classed have also been
analysed, and that their resembling qualities have been recognised
amidst diverse groups of qualities.

Of the classes marked by popular language it is worth while to
distinguish two sorts (_cf._ chap. xix. Sec. 4): Kinds, and those having
but few points of agreement.

But the popular classifications, made by language and the primitive
arts, are very imperfect. They omit innumerable things which have not
been found useful or noxious, or have bee