lated before, but in negative contexts, and with no appreciation of its power — see
p. 137), and can only specify the guts of the operating machine, not the three
principles that established the range and power of Darwin's revolution in human
thought. Rather, these three larger principles, in defining the Darwinian essence,
take the guts of the machine, and declare its simple operation sufficient to generate
the entire history of life in a philosophical manner that could not have been more
contrary to all previous, and cherished, assumptions of Western life and science.
The three principles that elevated natural selection from the guts of a working
machine to a radical explanation of the mechanism of life's history can best be
exemplified under the general categories of agency, efficacy, and scope. I treat
them in this specific order because the logic of Darwin's own development so
proceeds (as I shall illustrate in Chapter 2), for the most radical claim comes first,
with assertions of complete power and full range of applicability then following.
AGENCY. The abstract mechanism requires a locus of action in a hierarchical
world, and Darwin insisted that the apparently intentional "benevolence" of nature
(as embodied in the good design of organisms and the harmony of ecosystems)
flowed entirely as side-consequences of this single causal locus, the most
"reductionistic" account available to the biology of Darwin's time. Darwin insisted
upon a virtually exceptionless, single-level theory, with organisms acting as the
locus of selection, and all "higher" order emerging, by the analog of Adam Smith's
invisible hand, from the (unconscious) "struggles" of organisms for their own
personal advantages as expressed in differential reproductive success. One can
hardly imagine a more radical reformulation of a domain that had unhesitatingly
been viewed as the primary manifestation for action of higher power in nature—
and Darwin's brave and single-minded insistence on the exclusivity of the
organismic level, although rarely appreciated by his contemporaries, ranks as the
most radical and most distinctive feature of his theory.
EFFICACY. Any reasonably honest and intelligent biologist could easily
understand that Darwin had identified a vera causa (or true cause) in natural
selection. Thus, the debate in his time (and, to some extent, in ours as well) never
centered upon the existence of natural selection as a genuine causal force in nature.
Virtually all anti-Darwinian biologists accepted the reality and action of natural
selection, but branded Darwin's force as a minor and negative mechanism, capable
only of the headsman's or executioner's role of removing the unfit, once the fit had
arisen by some other route, as yet unidentified. This other route, they believed,
would provide the centerpiece of a "real" evolutionary theory, capable of
explaining the origin of novelties. Darwin insisted that his admittedly weak and
negative force of natural selection could, nonetheless, under certain assumptions
(later proved valid) about the nature of variation, act as the positive mechanism of
evolutionary novelty— that is, could "create the fit" as well as eliminate the
unfit—by slowly accumulating the positive effects of favorable variations through
innumerable generations.
Defining and Revising the Structure of Evolutionary Theory 15