596 THE STRUCTURE OF EVOLUTIONARY THEORY
In the context of this conscious and directed search, we should not be
surprised that Darwin's theory of natural selection rests upon the same central
paradox that fueled Adam Smith's system: postulate a cause based on individuals
ruthlessly pursuing their own benefits; an ordered polity will then arise as an
incidental side consequence. No dismissal of Paley's omniscient God as the direct
creator of general order could possibly have been more incisive, or more radical.
We can therefore understand why Darwin insisted so strongly upon a single-level
theory of natural selection—with struggle among individual bodies as a virtually
exclusive locus of causality (see Chapters 2 and 3 for extended analysis). The
downward shift of agency, from a purposively benevolent deity to the amoral self-
interest of organisms, embodies the most distinctive and radical aspect of
Darwinism.
Given Darwin's intense and conscious desire to restrict causality to competing
organisms, I have been particularly struck, in researching and writing this book, by
the inability of all-the most diligent, and most thoughtful, early selectionists to
make such a system work fully and consistently—despite intense and clearly
focussed efforts to "cash out" Darwin's vision. As discussed in Chapters 3 and 5,
only two early evolutionists fully grasped the meaning of natural selection, and the
logic behind Darwin's restriction to the level of organisms. The first, August
Weismann, defended Darwin's system with utmost zeal, as he spoke with pride
about the Allmacht (all-might, or omnipotence) of natural selection. He began by
advocating rigid adherence to Darwin's level of organisms. But, in fighting the
resurgent Lamarckism of late 19th century thought, Weismann had to descend a
notch to postulate important "germinal selection" at the level of hereditary units.
Late in his career, he recognized the logical generality enjoined by his admission
of a second locus—which selection can work on objects with requisite properties at
any level of the genealogical hierarchy. Weismann therefore articulated a fully
hierarchical model of selection operating at several levels both below and above
individual organisms. Moreover, he developed this full theory not in retreat or as a
hedge, but as a compelling extension of selection's central logic—and as further
testimony to an Allmacht even more inclusive.
The second, Hugo de Vries, postulated a macromutational mechanism that
logically precluded the production of new species by gradual selection of
intrapopulational variation. In so doing, he committed intellectual parricide against
his personal hero, Charles Darwin—and this mental act caused him great
psychological distress. He assuaged his feelings of guilt, and showed his
understanding of the abstract logic of selection, by insisting that he remained loyal
to Darwinism—but at a higher level of selection among species, rather than among
organisms (see pp. 446-451).
We must also not neglect the man who had invested the most effort in holding
the line at organismal selection, and who had the most to lose if such a restriction
could not work—Charles Darwin himself. Darwin struggled mightily to bring all
evolutionary phenomena, including a host of apparently exceptional items from
hymenopteran colonies to prevention of interspecific hybridization, under the
umbrella of organismic selection, often with truly ingenious