.

2. Although the majority of structures and instincts met with in the
animal kingdom are in a marvellous degree suited to the performance of
their functions and uses, it is nevertheless far from being an
invariable rule that the suitability is perfect. Thus, for instance,
even in the case of the eye--which is perhaps the most wonderful and
most highly elaborated structure in organic nature--it is demonstrable
that the organ, considered as an optical instrument, is not ideally
perfect; so that, if it were an artificial production, opticians would
know how to improve it. And as for instinct, numberless cases might be
adduced of imperfection, ranging in all degrees from a slight deficiency
to fatal blundering.

Now if all organic structures are supposed to be mechanisms designed by
the Deity, and all instincts are supposed to be mental attributes
implanted by Him, it becomes unintelligible that in the result the human
mind should thus be able to perceive, either an ignorance of natural
principles in the Author of nature, or a singular absence of thought in
applying His knowledge. But, on the other hand, if all the structures
and instincts are supposed to be due to natural selection (whether alone
or in conjunction with other natural causes), we have no need to feel
staggered at flagrant cases of imperfection; we have only to wonder at
the number of cases in which perfection, more or less complete, has been
attained.

3. Lastly, there is still another general consideration, and one which
appeals to my mind as of immense weight. The question, it will be
remembered, lies between beneficent design and natural selection, and I
think that the consideration about to be adduced is in itself alone
sufficient to decide the question.

This consideration is that amid all the millions of mechanisms and
instincts in the animal kingdom, there is no one instance of a
mechanism or instinct occurring in one species for the exclusive benefit
of another species, although there are a few cases in which a mechanism
or instinct that is of benefit to its possessor has come also to be
utilised by other species. Now, on the beneficent design theory it is
impossible to explain why, when all the mechanisms in the same species
are invariably correlated for the benefit of that species, there should
never be any such correlation between mechanisms in different species,
or why the same remark should apply to instincts. For how magnificent a
displa