44

Logic II 43a.

{Section title: Classes determined by examples, not by definition.}

There are two remarks [which?] more about natural classification
which, though they are commonplace enough, cannot
decently be passed by without recognition. They
have both just been virtually said, but they had better
be more explicitly expressed and put in a light in which
their bearing upon the practice of classification shall
be plain. The descriptive definition of a natural class, according to
what I have been saying, is not the essence of it. It is
only an enumeration of its members. A description
of a natural class must be founded upon samples of
it or typical examples. Possibly a zoologist or
a botanist may have so definite a conception of
what a species is that a single type-specimen may
enable him to say whether a form of which he finds
a specimen belongs to the same species or not. But
it will be much safer to have a large number of indi-