Introduction.
In his study of evolution, or arrange-
ment of organisms into taxa, the systematic biologist
makes
continual use of the concepts of homology and
analogy. The historical
development and current
meanings of these concepts are of interest both
because
they help show how the science of systematics is done,
and
because of the intriguing frequency with which
philosophically mistaken
arguments have intruded into
the science.
The fundamental aim of taxonomy is to classify
organisms into groups in a
biologically meaningful way.
The Linnean hierarchy, built along lines
formally pro-
posed by Aristotle, is the
familiar result. A major pur-
pose of
evolutionary biology is to discover the actual
diverging sequences of
organisms, commonly described
by phylogenetic trees, and the causes of
those diver-
gences.
