branches of the Darwinian essence in this particular picture—are also so essential
that any severing of a complete branch either kills, or so seriously compromises,
the entire theory that a new name and basic structure becomes essential.
We now reach the interesting point where excisions and regraftings preserve
the essential nature of an intellectual structure, but with two quite different levels
of change and revision, as characterized by Falconer's and Darwin's competing
metaphors for the Duomo of Milan. I would argue that a severing low on any one
of the three major branches corresponds with a revision profound enough to
validate the more interesting Falconerian version of major revision upon a
conserved foundation. (The Falconerian model is, in this sense, a Goldilockean
solution itself, between the "too much" of full destruction and the "too little" of
minor cosmetic revision.) On the other hand, the severing of a subbranch of one of
the three branches symbolizes a less portentous change, closer to Darwinian
models for the Milanese Duomo— an alteration of important visual elements, but
without change in the basic framework.
My fascination with the current state of evolutionary theory, at least as I read
current developments in both logic and empirics, lies in its close conformity to the
Falconerian model—with enough continuity to make the past history of the field so
informative (and so persistently, even emotionally, compelling), but with enough
deep difference and intellectual fascination to stimulate anyone with a thirst for the
intriguing mode of novelty that jars previous certainty, but does not throw a field
into the total anarchy of complete rebuilding (not a bad thing either, but far from
the actual circumstance in this case).
To summarize my views on the utility of such a model for the essence of
Darwinian logic, I will designate three levels of potential cuts or excisions to this
organic (and logical) coral of the structure of evolutionary theory, as originally
formulated by Darwin in the Origin of Species, and as revised in a Falconerian way
in recent decades. The most inclusive and most fundamental K-cuts (killing cuts)
sever at least one of the three central principles of Darwinian logic and thereby
destroy the theory tout court. The second level of R-cuts (revision cuts) removes
enough of the original form on one of the three central branches to ensure that the
new (and stronger or more arborescent) branch, in regrowing from the cut, will
build a theory with an intact Darwinian foundation, but with a general form
sufficiently expanded, revised or reconstructed to present an interestingly different
structure of general explanation—the Falconerian model for the Duomo of Milan.
Finally, the third level of S-cuts (subsidiary cuts) affects only a subbranch of one
of the three major branches, and therefore reformulates the general theory in
interesting ways, while leaving the basic structure of explanation intact—the
Darwinian model for the Duomo of Milan.
I wrote this book because I believe that all three pillars, branches, or tripod
legs, representing the three fundamental principles of Darwinian central logic, have
been subjected to fascinating R-cuts that have given us at least the
20 THE STRUCTURE OF EVOLUTIONARY THEORY