2 1 3A r g u m e n t s f r o m A n a l o g ythe same proof that the eye was made for vision, as there is that the telescope
was made for assisting it. They are made upon the same principles; both being
adjusted to the laws by which the transmission and refraction of rays of light
are regulated. I speak not of the origin of the laws themselves; but such laws
being fixed, the construction in both cases is adapted to them....
To some it may appear a difference sufficient to destroy all similitude
between the eye and the telescope, that the one is a perceiving organ, the other
an unperceiving instrument. The fact is that they are both instruments. And as
to the mechanism, at least as to mechanism being employed, and even as to
the kind of it, this circumstance varies not the analogy at all.... The end is the
same; the means are the same. The purpose in both is alike; the contrivance for
accomplishing that purpose is in both alike. The lenses of the telescopes, and
the humors of the eye, bear a complete resemblance to one another, in their
figure, their position, and in their power over the rays of light, viz. in bringing
each pencil to a point at the right distance from the lens; namely, in the eye, at
the exact place where the membrane is spread to receive it. How is it possible,
under circumstances of such close affinity, and under the operation of equal
evidence, to exclude contrivance from the one; yet to acknowledge the proof of
contrivance having been employed, as the plainest and clearest of all proposi-
tions, in the other?...
Were there no example in the world of contrivance except that of the eye,
it would be alone sufficient to support the conclusion, which we draw from
it, as to the necessity of an intelligent Creator.... The proof is not a conclu-
sion that lies at the end of a chain of reasoning, of which chain each instance
of contrivance is only a link, and of which, if one link fail, the whole fails; but
it is an argument separately supplied by every separate example. An error in
stating an example affects only that example. The argument is cumulative in
the fullest sense of that term. The eye proves it without the ear; the ear without
the eye. The proof in each example is complete; for when the design of the part
and the conduciveness of its structure to that design is shown, the mind may
set itself at rest; no further consideration can detract anything from the force
of the example.notEs
(^1) Gilbert Harman deserves much credit for calling attention to the importance of inferences to
the best explanation; see, for example, his Thought (Princeton, NJ: Princeton University Press,
1973). A similar form of argument called abduction was analyzed long ago by Charles Sanders
Peirce; see, for example, his Collected Papers of Charles Sanders Peirce, Vol. 5 (Cambridge, MA:
Harvard University Press, 1931), 189. A wonderful recent discussion is Peter Lipton, Inference to
the Best Explanation (London: Routledge, 1991).
(^2) Sir Arthur Conan Doyle, “Silver Blaze,” The Complete Sherlock Holmes, Vol. 1 (Garden City, NY:
Doubleday, 1930), 349. The stories describe Holmes as a master of deduction, but his arguments
are inductive as we define the terms.
(^3) This discussion in many ways parallels and is indebted to the fifth chapter of W. V. Quine and
J. S. Ullian, The Web of Belief, 2nd ed. (New York: Random House, 1978).
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