But may not this inference be presumptuous? Have we any right to
assume that the Creator works by intellectual powers like those of
men? If we must compare the eye to an optical instrument, we ought
in imagination to take a thick layer of transparent tissue, with a
nerve sensitive to light beneath, and then suppose every part of
this layer to be continually changing slowly in density, so as to
separate into layers of different densities and thicknesses, placed
at different distances from each other, and with the surfaces of
each layer slowly changing in form. Further, we must suppose that
there is a power always intently watching each slight accidental
alteration in the transparent layers, and carefully selecting each
alteration which, under varied circumstances, may in any way, or in
any degree, tend to produce a distincter image. We must suppose
each new state of the instrument to be multiplied by the million,
and each to be preserved till a better be produced, and then the old
ones to be destroyed. In living bodies variation will cause the
slight alterations, generation will multiply them almost infinitely,
and natural selection will pick out with unerring skill each
improvement. Let this process go on for millions on millions of
years, and during each year on millions of individuals of many
kinds; and may we not believe that a living optical instrument might
thus be formed as superior to one of glass as the works of the
Creator are to those of man?" {92a}

Mr. Darwin does not in this passage deny design, or cunning, point
blank; he was not given to denying things point blank, nor is it
immediately apparent that he is denying design at all, for he does
not emphasize and call attention to the fact that the VARIATIONS on
whose accumulation he relies for his ultimate specific difference
are accidental, and, to use his own words, in the passage last