to which comparative anatomy introduces us; partly because they
furnish one of the clearest proofs of evolution, and partly because
they most strikingly refute the teleology of certain philosophers. The
theory of evolution enables us to give a very simple explanation of
these phenomena.

We have to look on them as organs which have fallen into disuse in the
course of many generations. With the decrease in the use of its
function, the organ itself shrivels up gradually, and finally
disappears. There is no other way of explaining rudimentary organs.
Hence they are also of great interest in philosophy; they show clearly
that the monistic or mechanical view of the organism is the only
correct one, and that the dualistic or teleological conception is
wrong. The ancient legend of the direct creation of man according to a
pre-conceived plan and the empty phrases about "design" in the
organism are completely shattered by them. It would be difficult to
conceive a more thorough refutation of teleology than is furnished by
the fact that all the higher animals have these rudimentary organs.

The theory of evolution finds its broadest inductive foundation in the
natural classification of living things, which arranges all the
various forms in larger and smaller groups, according to their degree
of affinity. These groupings or categories of classification--the
varieties, species, genera, families, orders, classes, etc.--show such
constant features of coordination and subordination that we are bound
to look on them as genealogical, and represent the whole system in the
form of a branching tree. This is the genealogical tree of the
variously related groups; their likeness in form is the expression of
a real affinity. As it is impossible to explain in any other way the
natural tree-like form of the system of organisms, we must regard it