Internalism and Laws of Form 299
formalism, the "philosophic anatomique" of the book (1818) that would secure his
reputation.
Geoffroy began by applying the chief formalist notion of unity of type to the
vertebrate skeleton. Reptiles, birds, and mammals presented minimal difficulty, but
fishes posed the key challenge to such a comprehensive view. Compared with
terrestrial vertebrates, fishes seemed so different in their anatomy of skull, fins, and
shoulder girdle, and so disparate in mode of respiration, that any notion of a
common plan must be deemed untenable if not fatuous prima facie. Cuvier had
argued on functional grounds that the uniqueness of several skeletal elements in
fishes testified to their fitness for swimming and breathing in water.
Geoffroy published a group of memoirs on the anatomy of fishes in 1807, the
first successes of his research program. Working primarily with bones of the
shoulder girdle, he found a putative homologue of the furcula (wishbone) in birds.
The functionalist credo that such a bone must exist "for" flight must therefore be
false. Rather, the furcula in birds, and its homolog in fishes (operating as an
additional rib in some species, and as an aid to opening the gills in others), must be
specialized representatives of an abstract element in the archetype of all
vertebrates. The form of the archetype holds priority, whereas diversified
functional utility only represents a set of secondary modifications, superimposed
by conditions of existence upon the primacy of underlying form. Thus, in his first
foray into formalism, Geoffroy codified the key idea of structural constraint: form
exerts both logical and temporal priority upon function; good designs exist in
abundance because the archetype includes this potential for secondary
modification; function does not create form, rather form finds function: "Without a
direct object in swimming animals, without a utility determined in advance, and
thrown, so to say, by chance into the field of organization, the furcula enters into
connection with the organs near it; and according to the manner in which this
association is formed, it takes on uses which are in some sense prescribed by them"
(Geoffroy, 1807, quoted in Appel, 1987, p. 87).
The boldest version of the formalist argument for vertebrates, strongly upheld
and extended by Geoffroy, hypothesizes a comprehensive unity of type across the
entire phylum—with all elements present in all species (if only in embryos, or
fused in adults), and with no new elements originating for specific functions. This
strict account embodies both meanings of constraint in their strongest versions—
the negative sense of limitation in restriction of elements to pieces of the
archetypal jigsaw puzzle; and the positive sense of directed channels providing
numerous, though ordered, possibilities for modified shapes (including forms as
yet unrealized on our planet, but predictable from the channels, and implied by
observed developmental pathways).
Geoffroy wrote in 1807 (quoted in Appel, 1987, p. 89): "It is known that
nature works constantly with the same materials. She is ingenious to vary only the
forms... One sees her tend always to cause the same elements to reappear, in the
same number, in the same circumstances, and with the same connections."