- Darwin famously characterized the Origin as "one long argument" without
explicitly stating "for what?" Assumptions about the focus of this long argument
have ranged from the restrictively narrow (for natural selection, or even for
evolution) to the overly broad (for application of the most general
hypotheticodeductive model in scientific argument, as Ghiselin has claimed). I take
a middle position and characterize the "long argument" as an attempt to establish a
methodological approach and intellectual foundation for rigorous analysis in
historical science—a foundation that could then be used to validate evolution. - The "long argument" for historical science operates at two poles—
methodological and theoretical. The methodological pole includes a set of
procedures for making strong inferences about phyletic history from data of an
imperfect record that cannot, in any case, "see" past causes directly, but can only
draw conclusions from preserved results of these causes. Darwin develops four
general procedures, all based on one of the three essential premises of his theory's
central logic: the explanation of large-scale results by extrapolation from short-
term processes. In order of decreasing information available for making the
required inference, these four procedures include: (1) extrapolation to longer times
and effects of evolutionary changes actually observed in historic times (usually by
analogy to domestication and horticulture); (2) exemplification and ordering of
several phenomena as sequential stages of a single historical process (fringing
reefs, barrier reefs and atolls as stages in the formation of coral reefs by subsidence
of central islands, for example); (3) inference of history as the only conceivable
coordinating explanation for a large set of otherwise disparate observations
(consilience); and (4) inference of history from single objects based on quirks,
oddities and imperfections that must denote pathways of prior change. - The theoretical pole rests upon the three essential components of
Darwinian logic: (1) agency, or organismal struggle as the appropriate (and nearly
exclusive) level of operation for natural selection; (2) efficacy, or natural selection
as the creative force of evolutionary change (with complexly coordinated sequelae
of inferred principles about the nature of variation, and of commitments to
gradualism and adaptationism as foci of evolutionary analysis); and (3) scope, or
extrapolationism (as described in point 4 just above). The logical coordination of
these commitments, and their establishment as a brilliantly coherent and
intellectually radical theory of evolution, can best be understood by recognizing
that Darwin transferred the paradoxical argument of Adam Smith's economics into
biology (best organization for the general polity arising as a side consequence of
permitting individuals to struggle for Aemselves alone) in order to devise a
mechanism—natural selection—that would acknowledge Paley's phenomenology
(the good design of organisms said harmony of ecosystems), while inverting its
causal basis in the most radical of all conceivable ways (explaining the central
phenomenon of adaptation by historical evolution rather than by immediate
creation, and recognizing nature's sensible order as a side consequence of
unfettered struggle among individuals, rather than a sign of divine intent and
benevolence).
60 THE STRUCTURE OF EVOLUTIONARY THEORY