316 THE STRUCTURE OF EVOLUTIONARY THEORY
Whewell ends with a striking musical analogy, arguing that formalism
conveys a certain pleasure and appreciation, but that full delight and instruction
require apprehension in terms of purpose:
To us this doctrine [of final causes or functionalism] appears like the
natural cadence of the tones to which we have so long been listening: and
without such a final strain our ears would have been left craving and
unsatisfied. We have been lingering long amid the harmonies of law and
symmetry, constancy and development; and these notes, though their music
was sweet and deep, must too often have sounded to the ear of our moral
nature, as vague and unmeaning melodies, floating in the air around us, but
conveying no definite thought, molded into no intelligible announcement
(1869, p. 495).The vertebrate archetype: constraint and nonadaptation
All biologists know that Richard Owen defined the terms analogy and homology in
their modern sense, and that he made a tripartite division of the second category
into general, special and serial (thus demonstrating the generative and
developmental, rather than the evolutionary, basis of his underlying concept—see
Chapter 10, pp. 10 70 - 1076, for an extensive analysis of Owen's categories in the
light of modern developmental biology). With this framework, constructed
specifically in the light of the formalist-functionalist debate, Owen could engage
the problem that Darwin would later designate as paramount in morphology—the
special homology of similar parts with divergent functions. "What can be more
curious," Darwin would write (1859, p. 434 and p. 112 of this book), "than that the
hand of a man, formed for grasping, that of a mole for digging, the leg of the horse,
the paddle of the porpoise, and the wing of the bat, should all be constructed on the
same pattern."
Surely, Owen reasoned, these underlying structural similarities could not be
explained by common utility—the category that he had designated as "analogy."
And thus, the "British Cuvier" explicitly contradicted the central belief of his
eponym by denying a functional explanation for homology: "The attempt to
explain, by the Cuvierian principles, the facts of special homology on the
hypothesis of the subserviency of the parts so determined to similar ends in
different animals—to say that the same or answerable bones occur in them because
they have to perform similar functions—involve [sic] many difficulties, and are
opposed by numerous phenomena" (Owen, 1848, p. 73).
Owen clearly accepts the common conceptual taxonomy of his generation, for
he argues that functionalism and formalism represent the only intelligible
interpretations of morphology. We rightly reject functionalism for special
homology, but if we deny formalism as well, then we retain, for explanation,
nothing but a stochastic "slough of despond": "With regard to the structural
correspondences manifested in the locomotive members; if the principle of special
adaptation fails to explain them, and we reject the idea of these correspondences as
manifestations of some archetypal exemplar on which it has