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Man Darwin admitted the extent to which this way of looking at nature
had remained with him: "I was not able to annul the influence of my
former belief, then almost universal, that each species had been
purposely created; and this led to my tacit assumption that every
detail of structure, excepting rudiments was of some special, though
unrecognized, service." Like Paley, Darwin began with artifice and
with familiar examples in order to win over his audience. Like Paley,
he employed repeated examples and rhetorical questions in order to
bring his reader to make the leap of faith which his theory required.
The same cast of mind carried over to Darwin's writing about natural
selection, and others were quick to point this out.

The third reason for Darwin's writing about natural selection as he
did was more straightforwardly scientific. In proposing the theory of
evolution by means of the mechanism of natural selection he was not
really supplying a mechanism at all. Rather, he was providing an
abstract account at a general level of how favorable variations might
be preserved. He had to keep his account at a certain level of
abstraction since, as he confessed, he could specify neither the laws
of variation nor the precise means by which variations were preserved.
The acceptability of his account depended on its plausibility and its
ability to explain in very general terms the sort of process which was
involved. He could neither show evolution at work nor provide a
complete example of the stages by which it had worked. The former
process was too slow while the record of its having occurred was too
fragmentary. Darwin's task was to explain away the lack of evidence
while repeatedly stressing the greater plausibility of his theory over
that of special creation. Whenever he was really in trouble he adopted
the same tactic as Lyell, Chambers, and Powell had done - he appealed
to the very principle which was at issue, the uniformity of nature. By
creatively confusing the metaphysical regulative principle of science
with particular empirical issues, his argument gained plausibility
from its circularity. John Tyndall put the point in the best possible
light in his highly controversial "Belfast Address" in 1874: "The
strength of the doctrine of Evolution consists, not in an experimental
demonstration (for the subject is hardly accessible to this mode of
proof), but in its general harmony with scientific thought."

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I

From the outset there were signs that trouble lay ahead at the hands
of outright opponents of evolution (e.g., Wilberforce), friendly foes
(Sedgwick), and sympathetic critics (e.g., Lyell). In the most famous
review of the Origin, Bishop Samuel Wilberforce deftly turned Darwin's
own language against him.