96 THE STRUCTURE OF EVOLUTIONARY THEORY
marked varieties, or between lesser varieties and individual differences.
These differences blend into each other in an insensible series; and a se-
ries impresses the mind with the idea of an actual passage. Hence I look
at individual differences, though of small interest to the systematist, as of
high importance for us, as being the first step towards such slight varie-
ties as are barely thought worth recording in works on natural history
(1859, p. 51).I need hardly stress Darwin's impact as one of the half dozen or so most
revolutionary thinkers in western history. I want, instead, to emphasize a more
curious aspect of his status—his continuing relevance, indeed his benevolent
hovering over almost all our current proceedings. We may revere Newton and
Lavoisier as men of equal impact, but do modern physicists and chemists actively
engage the ideas of these founders, as they pursue their daily work? Darwin, on the
other hand, continues to bestride our world like a colossus—so much so that I can
only begin this book on the structure of evolutionary theory by laying out Darwin's
detailed vision as a modern starting point, a current orthodoxy only lightly
modified by more than a century of work. I do, in this book, advocate some major
restructuring, in the light of new concepts and findings, and with the approbation
of more and more colleagues as our understanding of evolution broadens. But
Darwin remains our context—and my proposed restructuring represents an
extension, not a replacement, of his vision. The hierarchical theory of selection
builds a world different from Darwin's in many important respects, but we do so by
extending his mechanism of selection to a larger realm than he acknowledged—
that is, to levels both below and above his focus on the struggle among organisms.
When Cassius spoke his words about Caesar (paraphrased above), he added
his puzzlement at Caesar's extraordinary success: "Upon what meat doth this our
Caesar feed, that he is grown so great." I shall argue in this chapter that Darwin's
continued, pervasive relevance arises from his capacity for revolutionary
innovation at two opposite poles of scientific practice—the immediate strategy of
formulating a methodology for everyday research, and the most general discussion
of causes and phenomena in the natural world (the questions that will not go away,
and that air continually from college bull sessions, to TV talk shows, to learned
treatises on the nature of things). Darwin's residence at both poles of immediate
methodology and broadest theoretical generality begins with his distinctive
attitude towards the central importance of daily, palpable events in nature, and
their power to account for all evolution by cumulation—hence my choice of an
opening topic for this chapter (see Fig. 2-1).
Caesar voiced his suspicions of Cassius, fearing men who think too much
(may all despots thus beware). But his grudging words of praise might well be
invoked to epitomize the reasons for Darwin's unparalleled success: "He reads
much; he is a great observer, and he looks quite through the deeds of men."