250 THE STRUCTURE OE EVOLUTIONARY THEORY
became stymied, and eventually surrendered, with pleasure in Weismann's case at
least, to the need for hierarchy in devising any complete system for the logic of
evolutionary explanation in selectionist terms—Weismann on subcellular selection
for explaining trends, Darwin on species selection for encompassing diversity.
Both men accepted causal hierarchy in the modern and valid sense of similar forces
working in distinct ways at different levels.
Very few evolutionists know anything about this history, and may therefore
doubt the importance of the subject. But downgrading on this criterion would
represent a great mistake rooted in the conservative premise that anything vital
must be easily visible in all contexts. Anyone tempted to accept such a basis for
dismissal should consider the conventional tales of rulers and conquerors—
virtually the only subject matter of so many secondary school and undergraduate
history courses—and recognize what modern scholars have taught us by probing
the hitherto invisible pathways of daily life among ordinary people. Compare the
overt and conventional history of diplomacy with the often more potent, but
academically invisible, history of technology.
Evolutionary thought began with hierarchy, wrongly conceived. Our
canonical theory of natural selection arose as an attempted rebuttal. The most
brilliant practitioners of that theory could not bring the argument to completion; so
both Weismann and Darwin brought hierarchy back, in a valid style this time, to
render the theory of selection both coherent and comprehensive. I previously
offered a choice of proverbs: you may view hierarchy as a bad penny or a pearl of
great price. But hierarchy, like the poor, has always been with us (and, perhaps,
shall inherit the earth as well!). This situation can only recall James Boswell's
famous statement about one of Dr. Johnson's colleagues who lamented that he had
tried to be a philosopher, but had failed because cheerfulness always broke
through. Too many of us have tried to be good Darwinian evolutionists, and have
felt discouraged because hierarchy always breaks in. I suggest that we rejoice—
with good cheer—and welcome an under appreciated and truly indispensable old
friend.