An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

THE CATEGORIES OR PREDICAMENTS. 195
"
The same consideration applies mutatis mutandis to real
kinds" in Nature, with the important difference that the
transition forms actually exist in large numbers. The real
kinds run into one another; between them there are margins
of debateable ground, as it were, objects which appear to
constitute a transition from one kind to another. Still, there
are natural divisions, marked off by typical differences which
are obvious and clear ; and in this sense we can maintain
that real kinds exist in Nature. The theory of Evolution
teaches that many, if not all, of them have descended from
a common stock, and forbids us to regard the divisions
between them as permanent ; but it has not taken away the
meaning of "real kinds." It has given them a relative
instead of an absolute stability.
It is
"
"
an interesting fact that the natural classifications,
in Botany and Zoology, were worked out before the Evolution
theory was generally accepted ; and Evolution has given
them a fuller meaning. A natural classification is now a
"
and the words
"
genealogical tree ;
kind,"
affinity,"
"family," are no longer mere metaphorical expressions.
"
genus,"