1188 THE STRUCTURE OF EVOLUTIONARY THEORY
Nevertheless, when philosophy bids us hearken and obey the lessons both of
mechanical and of teleological interpretation, the precept is hard to follow: so
that oftentimes it has come to pass, just as in Bacon's day, that a leaning to the
side of the final cause "hath intercepted the severe and diligent inquiry of all
real and physical causes," and has brought it about that "the search of the
physical cause hath been neglected and passed in silence." So long and so far
as "fortuitous variation" and the "survival of the fittest" remain engrained as
fundamental and satisfactory hypotheses in the philosophy of biology, so long
will these "satisfactory and specious causes" tend to stay "severe and diligent
inquiry," "to the great arrest and prejudice of future discovery."D'Arcy Thompson's citation of Bacon's famous critique does not imply any
personal distaste for the subject of excellent adaptation or final causation in general.
Quite to the contrary, D'Arcy Thompson's focus on geometric beauty and mechanical
optimality led him to emphasize the loveliest and most stunningly efficient of organic
designs. Thus, his complaint did not lie with the existence of adaptation, but with the
too-facile Darwinian assumption that such final causes imply a mode of construction
explicitly powered by the value of the developing adaptation itself—in other words, a
functionalist mechanism like natural selection. The nub of D'Arcy Thompson's
system, and his reason for emphasizing the different statuses of efficient and final
causation, resides in his conviction that efficient causes of physical construction craft
final causes as automatic consequences—thus obviating the need for a special
category of mechanisms (again like natural selection) to explain biological
adaptation. D'Arcy Thompson expresses his admiration and feeling for final causes in
one of his loveliest prose flourishes (p. 3):
Time out of mind, it has been by way of the "final cause," by the teleological
concept of "end," of "purpose," or of "design," in one or another of its many
forms (for its moods are many), that men have been chiefly wont to explain
the phenomena of the living world; and it will be so while men have eyes to
see and ears to hear withal. With Galen, as with Aristotle, it was the
physician's way; with John Ray, as with Aristotle, it was the naturalist's way;
with Kant as with Aristotle, it was the philosopher's way. It was the old
Hebrew way, and has its splendid setting in the story that God made "every
plant of the field before it was in the earth, and every herb of the field before it
grew." It is a common way, and a great way; for it brings with it a glimpse of
a great vision, and it lies deep as the love of nature in the hearts of men.As the last step in his general argument, D'Arcy Thompson then asks us to
consider how far the simplest and most direct style of efficient causation might carry
us in explaining adaptive organic form. Perhaps many features owe their geometric
optimality—leading to maximization of utility, or final cause, as well—to the
simplest mechanism of direct shaping by the physical forces most relevant to the
behaviors of the organism in its daily struggles for