evidence, to exclude contrivance in the case of the eye, yet to
acknowledge the proof of contrivance having been employed, as the
plainest and clearest of all propositions in the case of the telescope?'

Well, the answer to be made is that only upon the hypothesis of special
creation can this analogy hold: on the hypothesis of evolution by
physical causes the evidence in the two cases is _not_ equal. For, upon
this hypothesis we have the eye beginning, not as a ready-made structure
prepared beforehand for the purposes of seeing, but as a mere
differentiation of the ends of nerves in the skin, probably in the first
instance to enable them better to discriminate changes of temperature.
Pigment having been laid down in these places the better to secure this
purpose (I use teleological terms for the sake of brevity), the
nerve-ending begins to distinguish between light and darkness. The
better to secure this further purpose, the simplest conceivable form of
lens begins to appear in the shape of small refractive bodies. Behind
these sensory cells are developed, forming the earliest indication of a
retina presenting a single layer. And so on, step by step, till we
reach the eye of an eagle.

Of course the teleologist will here answer--'The fact of such a gradual
building up is no argument against design: whether the structure
appeared on a sudden or was the result of a slow elaboration, the marks
of design in either case occur in the structure as it stands.' All of
which is very true; but I am not maintaining that the fact of a gradual
development _in itself_ does affect the argument from design. I am
maintaining that it only does so because it reveals the possibility
(excluded by the hypothesis of sudden or special creation) of the
structure having been proximately due to the operation of physical
causes. Thus, for the value of argument, let us assume that natural