Darwin and the Darwinians 177
there will be a considerable revolution in natural history. Systematists will be able
to pursue their labours as at present; but they will not be incessantly haunted by the
shadowy doubt whether this or that form be a true species. This, I feel sure and I speak
after experience, will be no slight relief. The endless disputes whether or not some fifty
species of British brambles are good species will cease. Systematists will have only to
decide (not that this will be easy) whether any form be sufficiently constant and distinct
from other forms, to be capable of definition; and if definable, whether the differences
be sufficiently important to deserve a specific name. This latter point will become a
far more essential consideration than it is at present; for differences, however slight,
between any two forms, if not blended by intermediate gradations, are looked at by
most naturalists as sufficient to raise both forms to the rank of species.
Hereafter we shall be compelled to acknowledge that the only distinction between
species and well-marked varieties is, that the latter are known, or believed, to be con-
nected at the present day by intermediate gradations whereas species were formerly
thus connected. Hence, without rejecting the consideration of the present existence
of intermediate gradations between any two forms, we shall be led to weigh more
carefully and to value higher the actual amount of difference between them. It is quite
possible that forms now generally acknowledged to be merely varieties may hereafter
be thought worthy of specific names; and in this case scientific and common language
will come into accordance. In short, we shall have to treat species in the same manner
as those naturalists treat genera, who admit that genera are merely artificial combina-
tions made for convenience. This may not be a cheering prospect; but we shall at least
be freed from the vain search for the undiscovered and undiscoverable essence of the
term species.^78It will be worthwhile to look at this matter closely, given the excerpts above as
cross bearings on the subtlety of Darwin’s views on species, and ask, has Darwin
said that species are “merely artificial combinations made for convenience?” The
answer is, no. He has said rather that naturalists shall be forced to treat them that
way. We have seen repeatedly that Darwin did not insist species were unreal, merely
that the rank was arbitrarily assigned and that we could not see if they were real
on the basis of characters. The reason the term species has no discoverable essence
(but does that imply it has a Real Essence in the Lockean sense?) is that each case
is different in the biological particulars. But they are separated, he says, in that the
“intergradations” between them are extinct. That is real enough. Darwin’s defini-
tion of species is simply that they do not interbreed, or, in the case of “unisexual”
organisms, that Natural Selection keeps them isolated in the “proper type” suited to
the conditions of life in which they live. In this I am concurring with Kottler’s and
Ghiselin’s conclusions; where Darwin seems to be a nominalist, he is in fact describ-
ing the problems of current taxonomic criteria, founded on creationist views of spe-
cies, and so describing what species are not.^79
The glossary to the later editions of the Origin does not give us a definition for
species, so we lack from Darwin the sort of epigrammatic slogan for species that so
many other writers have given us, and even if it had, it would be the definition of the
(^78) Op. cit., 371.
(^79) Kottler 1978, 293f, Ghiselin 1984.