98 THE STRUCTURE OF EVOLUTIONARY THEORY
now, and might be engaged empirically by studies of adaptation and heredity. But
the more important primary force, the source of natural order and the ultimate
cause of human mentality, lurked in the background of time's immensity, and at the
inaccessible interior of the very nature of matter. This characterization creates an
intolerable dilemma for anyone who holds (as Darwin did) that science must be
defined as testable doing, not just noble thinking. Recalling my opening quip,
Lamarck's system virtually mocked the empirical approach to science, and
forestalled any growing confidence in evolution: what is important cannot be seen;
what can be seen is not important.
Darwin used a brilliant argument to cut through this dilemma, thus making
the study of evolution a practical science. He acknowledged Lamarck's implied
claim that small scale adaptation to local environment defines the tractable subject
matter of evolution. But he refuted the disabling contention that adaptation in this
mode only diverted the "real" force of evolution into side channels and dead ends.
And he revised previous evolutionary thinking in the most radical way—by
denying that Lamarck's "real" force existed at all, and by encompassing its
supposed results as consequences of the "subsidiary" force accumulated to
grandeur by the simple expedient of relentless action over sufficient time. Darwin
established our profession not only by discovering a force—natural selection—that
seems both powerful and true; he also, perhaps more importantly, made evolution
accessible to science by granting to empiricists their most precious gifts of
tractability and testability. The essence of Darwin's theory (specified in the next
section) owes as much to his practical triumph at this immediate scale of daily
work, as to his broadest perception that western views of nature had been seriously
awry, and largely backwards.
Darwin, as we all know, began the last chapter of the Origin with a claim that
"this whole volume is one long argument" (1859, p. 459). Fine, but an argument
for what? For evolution itself? In part, of course, but such a general theme cannot
mark the full intent of Darwin's statement, for the bulk of the Origin moves well
beyond the basic arguments for evolution's factuality, as Darwin proceeds to craft a
defense for natural selection and for the philosophy of nature so entailed. "One
long argument" for natural selection, then? Again, in part; but we now confront the
obverse of my last statement: too much of the Origin details basic evidence for
evolution, independent of any particular mechanism of change. Instead, we must
ask what deeper subject underlies both the defense of evolution as a fact and the
proposal of a mechanism to explain its operation? How should we characterize the
"one long argument" that pervades the entire book?
Ghiselin (1969) correctly identified the underlying theme as the construction,
and defense by example, of a methodology—a mode of practice—for testing both
the fact and mechanism of evolutionary change. But I cannot agree with Ghiselin
that Darwin's consistent use of "hypothetico-deductive" reasoning constitutes his
long argument (see Kitcher, 1985), for this style of scientific procedure, whatever
its merits or problems, has been advocated as a general methodology for all
scientific activity (see Hempel, 1965). Darwin, I