ever will be, a matter of
knowledge in the scientific sense. At the most, we can see for ourselves
only that selection does bring about changes at least as great as the
differences between natural species. The evidence for this we have
before our eyes, if we choose to see, on a stock farm; in the breeding
yards of any keeper of "fancy" animals; or in the nursery gardens of any
florist. So far, Huxley accepted the Darwinian principle as a definite
contribution to knowledge; and so far the whole body of biologists has
followed him. Beyond this the truth of the Darwinian principle is a
matter of inference or judgment; of balancing probabilities and
improbabilities. In multitude of counsellors there is said to be wisdom,
and what we learn from the counsellors of biology all over the world is
that some maintain that natural selection is the only probable agency in
effecting evolution, and that it is competent to account for all the
changes which we know to have taken place; others hold that its probable
influence has been over-rated; and others, again, think that it has been
one of the many causes that have brought about the kaleidoscopic variety
of organic nature. Huxley remained to the last among those who
distinguished in the clearest way between natural selection as an
exceedingly ingenious and probable hypothesis, and a proved cause; and
he was always careful, especially when he was writing for or speaking in
the presence of those who like himself accepted the fact of evolution as
proven, to distinguish between this provisional hypothesis as to how
evolution had come about, and definite knowledge that it had come about
in this way. Two passages from Huxley's writings, one written in 1860 in
the _Westminster Review_, and the second written in 1893, in the preface
to the volume of his collected essays which contained a reprint of the
_Westminster_ article, will make plain the continuity of Huxley's
attitude:

"There is no fault to be found with Mr. Darwin's method, then;
but it is another question whether he has fulfilled all the
conditions imposed by that method. Is it satisfactorily proved,
in fact, that species may be originated by selection? That there
is such a thing as natural selection? That none of the phenomena
exhibited by species are inconsistent with the origin of species
in this way? If these questions can be answered in the
affirmative, Mr. Darwin's view steps out of t