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Jettison the Arguments, or the Rule?
The Place of Darwinian Theological Themata in
Evolutionary Reasoning
Paul A. Nelson
Department of Philosophy
University of Chicago
1050 East 59th Street
Chicago, IL 60637
Introduction
"No biologist today," observes Douglas Futuyma, "would
think of submitting a paper entitled 'New evidence for evolution;'
it simply has not been an issue for a century." [1] Whether
they see it as an issue or not, however, biologists today still
explain (in textbooks, for instance) why they think evolution
is true. In other words, they regularly make a case for the theory.
On these occasions, an odd thing often happens. While presenting
a line of evidence or argument for evolution, the author will,
as a premise of his argument, make a theological claim. The case
for evolution, in short, takes an unmistakably theological turn.
In their biology textbook A View of Life, for instance,
Salvador Luria, Stephen Jay Gould, and Sam Singer argue as follows:
A whale's flipper, a man's arm, a bird's wing, and a dog's foreleg...perform
functions about as different and varied as styles of locomotion in vertebrates
can be, yet all are built of the same bones. Why would God have used the same
building blocks, and distorted and twisted them in such odd ways, if He had
simply set out to make the best swimming, running, and flying machines? The
common structure must reflect common descent from an ancestor possessing these
bones. [2]
Consider two other examples, drawn in both cases from the technical
literature, where the theology is implicit under the rubric of
"intelligent design" -- as expressed, for instance,
by George Williams on the vertebrate retina:
...the optic nerve aris[es] on the wrong side of the sensory layer so that
it must go through a hole in the retina to get to the brain. The diameter
of the nerve is far greater than that of any retinal blood vessel. That means
a large hole, and wherever it is there will be no vision. This is the reason
for the blind spot, about 30 degrees right of the point of focus in the right
eye, 30 degrees to the left in the left...
There would be no blind spot if the vertebrate eye were really intelligently
designed. In fact it is stupidly designed, because it embodies many functionally
arbitrary or maladaptive features, of which the inversion of the retina is
merely one example. These features are there, not for functional but for purely
historical reasons. [3]
Or consider Bruce Alberts on protein synthesis and ribosomes:
...the mechanism of protein synthesis seems complex and awkward
compared to other biological processes that evolved later and
were therefore based on protein catalysis....In other words,
cells -- unlike computers -- are not optimally designed. Instead
what they are today is in large part a reflection of their past
history (Jacob, 1977). The ribosome is a notable example. As
a machine for making proteins, the ribosome seems so awkward
as to be a bore both for teachers to teach and for students to
learn. Its many pieces seem to make no conceptual sense at all,
especially when compared to the elegantly-designed pieces of
a DNA replication machine....Only when viewed as a historical
relic does the ribosome come alive. [4]
Now all this might be of little moment, were it not that these
arguments sit uncomfortably with a widely advocated philosophical
doctrine. It is generally held that evolutionary theory, like
other natural sciences, employs necessarily a methodology according
to which one cannot in scientific reasoning refer to "God,"
"the Creator," "creation" (understood as the
act of a divine intelligence), or other theological concepts.
Evolutionary biologists cite a variety of arguments in support
of this view, or argue that in all events methodological naturalism
(as the view has come to be known) stands very much at the foundation
of the modern scientific outlook. [5]
Thus it is a point of considerable interest that, while presenting
the "fact" of evolution (in writing introductory textbooks
or encyclopedia articles, for instance), or in reasoning about
organisms generally, many evolutionary biologists appeal to theology,
or to aesthetic and teleological judgments (e.g., "optimal
design," where the designing cause is an optimally acting
and all-knowing intelligence) functionally indistinguishable from
theology. This is noteworthy on at least two counts.
First, the demonstrable role of theology in evolutionary explanation
provides evidence (or counterarguments) against the soundness
of the philosophical doctrine of methodological naturalism. Methodological
naturalism has lately come under critical scrutiny. [6] This essay
provides some raw materials for that project, by showing how theological
premises bear directly on the content of evolutionary explanations.
Secondly, this essay suggests that the received understanding
of such questions as the significance of homologous patterns may
be skewed by unjustified theological premises. In arguing for
evolution, and in explaining the patterns of natural history,
biologists have grown accustomed to making claims about what a
creator would or would not have done. For this practice, they
have the example of the Origin of Species itself, and indeed,
Darwin's writings generally, where arguments of the sort at issue
play an important role in the case for evolution.
We do not inherit a theology, however, as we do our hair color.
We should adopt, or reject it, in terms of its coherence and correspondence
with truth -- especially, for biologists, where that theology
bears directly on one's understanding of the natural world.
The Imperfection Argument
In his History of Creation, Ernst Haeckel argued that
"even if we knew absolutely nothing of the other phenomena
of development, we should be obliged to believe in the truth of
the Theory of Descent, solely on the ground of the existence of
rudimentary organs." [7] Under the heading of "Dysteleology,"
Haeckel gathered a number of apparently useless or imperfect structures
that, he argued, could be reconciled with the theory of creation
only by "ludicrous" ad hoc conjectures. In laying great
stress on the evidential force of imperfection, Haeckel followed
Darwin's lead. Throughout his entire corpus, Darwin is never stronger
or more bitter in his language than when condemning the failed
teleology of theories of creation, which impute imperfect organic
design to the direct intent of a rational and benevolent creator.
Many current evolutionists stand squarely in this tradition.
Arguments that trade on intuitions about the nature of God --
namely, that from his wisdom and perfection he would create only
optimal or perfect designs -- occur widely in the recent evolutionary
literature, in a variety of contexts. [8] Doubtless the most influential
formulations, however, occur in the writings of Stephen Jay Gould.
Since many authors draw on Gould's formulations, I will consider
them here in detail (although, as noted, the same argument --
varying only in the particular organic design being considered
-- is made by many others).
The following passages are all drawn from Gould's writings.
While not structured formally as a series of premises leading
to a conclusion, each passage does contain the elements of the
argument, and expresses it either implicitly or explicitly.
The theory of natural selection would never have replaced the doctrine of
divine creation if evident, admirable design pervaded all organisms. Charles
Darwin understood this, and he focused on features that would be out of place
in a world constructed by perfect wisdom. ... Darwin even wrote an entire
book on orchids to argue that the structures evolved to ensure fertilization
by insects are jerry-built of available parts used by ancestors for other
purposes. Orchids are Rube Goldberg machines; a perfect engineer would certainly
have come up with something better. This principle remains true today. The
best illustrations of adaptation by evolution are the ones that strike our
intuition as peculiar or bizarre. [9]
Odd arrangements and funny solutions are the proof of evolution -- paths
that a sensible God would never tread but that a natural process, constrained
by history, follows perforce. [10]
The proof that evolution, and not the fiat of a rational agent, has built
organisms lies in the imperfections that record a history of descent and refute
creation from nothing. ... Adaptation does not follow the blueprints of a
perfect engineer. [11]
Evolution lies exposed in the imperfections that record a history of descent.
Why should a rat run, a bat fly, a porpoise swim, and I type this essay with
structures built of the same bones unless we all inherited them from a common
ancestor? An engineer, starting from scratch, could design better limbs in
each case. [12]
But how can a scientist infer history from single objects? This most common
of historical dilemmas has a somewhat paradoxical solution. Darwin answers
that we must look for imperfections and oddities, because any perfection in
organic design or ecology obliterates the paths of history and might have
been created as we find it. This principle of imperfection became Darwin's
most common guide. ... I like to call it the "panda principle" in
honor of my favorite example -- the highly inefficient, but serviceable, false
thumb of the panda. [13]
It will be useful to formalize Gould's argument. I have drawn
the following premises from the cited passages.
1. If p is an instance of organic design, then p was produced
either by a wise creator, or by descent with modification (evolution).
2. If p (an instance of organic design) was produced by a
wise creator, then p should be perfect (or should exhibit no
imperfections).
3. Organic design p is not perfect (or exhibits imperfections).
From these premises, the conclusion follows that:
Organic design p was not produced by a wise creator, but by descent with
modification. Some organic designs are evidence of evolution.
Note that premises 1 and 2 are theological; they refer directly
to a creator, and the actions expected of him. Gould's terms for
the creator include "a perfect engineer," "a sensible
God," "a rational agent," and "a wise creator."
Note further that premises 2 and 3 refer to "perfection,"
and we may reasonably infer from the cited passages that Gould
holds that humans can readily discern the presence or absence
of perfection when they examine organic designs.
The conclusion requires of course both that perfection and
imperfection be patent qualities of organic design, and that a
wise creator would only create perfect organic designs. If these
premises are granted, it will follow that any imperfect organic
design is not the product of a wise creator. Rather it has come
to be via the historically contingent processes of descent with
modification.
And, according to Gould, examples of imperfect organic design
abound. He writes of "vestigial organs," "odd biogeographic
distributions made sensible only as products of history,"
and "adaptations as contrivances jury-rigged from parts available"
[14] -- all of which, on the imperfection argument, provide evidence
for descent.
Some Problems with the Imperfection Argument
The imperfection argument for evolution is popular and compelling.
It draws on widely shared intuitions about God and the nature
and history of the structure of organisms. Discussing the argument
with philosophers and biologists, I was struck by how many of
them accepted it unreservedly as an impeccable piece of scientific
reasoning.
Despite its wide appeal, however, the argument is also deeply
problematical. The argument employs theological concepts, such
as "a wise creator," and aesthetic or teleological notions,
"perfection" and "imperfection," that cannot
perform the analytical and empirical work required of them. Each
premise of the argument is attended with difficulties.
Premise 1. "If p is an instance of organic design, then
p was produced either by a wise creator, or by descent with modification."
In this section, I will assume that the concept "wise
creator" and our ordinary notions of biological perfection
and imperfection are unambiguous, that is, they are understood
in the same way by all observers (assumptions which will be at
issue below). I want first to examine a lesser difficulty, namely,
that given our ordinary notions, the first premise of the imperfection
argument is a false dichotomy.
The imperfection argument presupposes a static theory of creation,
according to which an organic design p appears today largely as
it was originally created. Yet few if any creationists would defend
such a theory. [15] In fact, they are likely to acknowledge that
some organic designs are biologically "imperfect," but
will argue that such imperfection is consistent with their theoretical
outlook. Not all "imperfections," therefore, would count
against the theory of special creation, or a discontinuous geometry
of organic form, as these structures would be expected under what
might be called a "dynamic" theory of creation. In such
cases the argument from divine wisdom will fail to hit its mark.
As an example, consider blind cave animals. Futuyma presents
the functionless lens and retina of the cave salamander as instances
of the imperfect workings of evolution. He then asks, "Do
we find evidence here of wise design?" [16] Yet in the same
year that Futuyma posed his question, two well-known creationists,
independently considering the same phenomenon, saw it as degenerative
change easily understood under a creation theory:
Blind cave fish with remnants of eyes...appear to have true
vestigial organs. These and similar degenerations apparently
have indeed resulted from typically disadvantageous mutations....When
hereditary changes are small enough to permit survival and reproduction,
vestiges may remain. However, these vestigial structures at best
are indicative of changes within limits; they are usually degenerative
changes within a species. [17]
So Futuyma's question has answers other than the one he presupposes.
In all likelihood the apparently poor design of the cave salamander's
eye is the consequence of evolutionary change, but such degenerative
changes can readily be accommodated within a dynamic theory of
creation.
Consider another example, the rudimentary wings of flightless
birds, which Naylor regards as true vestigial structures whose
existence contradicts the theory of creation. [18] The Dutch creationist
Hendrik Murris, however, in a discussion of genetic drift and
the limits of variation, argues:
Suppose that (as an oversimplified example) the allele 'A'
imparts the ability to fly , while 'a' signifies flightlessness.
If birds with AA and Aa combinations arrive and breed on an island
where they have no natural enemies, the flightless aa individuals
which will inevitably be hatched will survive. Some generations
later, according to our model experiment, the entire population
could be flightless! [19]
Murris goes on to argue that within the theory of creation,
known genetic processes may explain the origin of some, though
not all, species of flightless birds. In a related analysis, the
German creationists Reinhard Junker and Siegfried Scherer explain
the origin of the rudimentary wings of flightless beetles and
insects as cases of degenerative microevolution. [20] Junker later
authored a systematic treatment of rudimentary organs and atavisms
within a creationist framework. [21] In these dynamic theories
of creation, extant organic designs are the products not just
of original creative intent, but also of the perturbing effects
of secondary causes, e.g., natural selection, mutation, or genetic
drift. [22] Thus, in any assessment of the optimality of an organic
design, the perturbing effects of secondary and natural causes
must be separated from original design (if such a historical reconstruction
is possible).
By presupposing a static theory of creation, the first premise
of the argument from divine wisdom describes a false dichotomy.
Of course, many supposedly imperfect organic designs, such as
human upright posture, or the human retina, cannot be explained
by a dynamic theory of creation as the consequence of simple degenerative
changes. A dynamic theory of creation can accommodate only certain
limited neutral or degenerative changes without contradicting
another of its main empirical tenets, namely, that genetic and
phenotypic variation is bounded. Most "vestigial" structures,
for instance, appear to mark out paths of phylogenetic branching
that are expressly denied by even the most flexibly dynamic theories
of creation. In any event, the argument from divine wisdom need
not, indeed should not, presuppose a static theory of creation.
That it does so often presuppose such a theory, however, should
alert us to the possibility that the argument may rest on other
problematical presuppositions.
Premise 2. "If p was produced by a wise creator, then
p should be perfect (or exhibit no imperfections)."
With this premise, we come upon the major theological difficulties
of the argument. In Gould's formulations, and in any formulation
which includes statements about the character and actions of a
"wise creator," the argument from divinew wisdom makes
theological claims which must be justified or explicated, irrespective
of the argument's empirical content. The structure of the argument
requires that "wise creator" be fixed objectively in
some way. In other words, any exponent of the argument must explain
(1) what a "wise creator" or a "sensible God"
is, and (2) what a "wise creator" would do.
To illustrate the first problem, assume for the moment that
we are able to identify an imperfect organic design p. Then suppose
our conception of the creator is similar to John Stuart Mill's:
the creator is benevolent and wise but not omnipotent. [23] This
creator's power is limited, and thus he would not be able to avoid
occasional design compromises. Some imperfections would necessarily
be included in the creation -- including, let us say, the imperfect
organic design p. On this view of the creator, the conclusion
that imperfection of organic design is evidence of descent with
modification would not follow in every case. Gould writes that
perfection alone cannot demonstrate descent, because "perfection
need not have a history." [24] If we employ Mill's conception
of the creator, however, imperfection need not have a history
either. [25] If a stapler that continually jams or a water pitcher
with a dribbling spout were designed de novo, they have no history
in an evolutionary sense -- yet both artifacts are manifestly
imperfect to anyone knowing their intended functions.
Mill's limited creator is heterodox (in the Christian tradition),
and some may wish to argue that one either defends the usual omnipotent
conception of the creator, or one defends no conception at all.
The point however is that we have no grounds within evolutionary
theory itself to exclude Mill's creator, or any one of a number
of conceivable creators whose natures allow imperfection. The
creator's place in the argument can't be filled by just any conception.
[26] To sustain the conclusion, "Imperfection of organic
design is evidence of descent," the argument from divine
wisdom requires a particular conception of the creator, namely,
the conventional picture of an omnipotent and beneficent artificer
(hereafter, the conventional conception). Thus, far from being
theologically neutral, the argument has a stake in the truth of
a particular theology.
I turn next to the problem of what a "wise creator"
would do, a problem related to the ambiguity of "perfection"
as an operational construct. Suppose we begin with the conventional
conception of the creator. According to the second premise of
the argument from divine wisdom, if a perfect God created the
world, we should expect to observe "perfect" organic
design -- but what sense should be attached to this term? Is it
possible that biological entities judged imperfect when considered
individually, might combine to form a macrosystem judged perfect?
Here, theological difficulties ordinarily ignored in any biological
analysis come crowding to the fore. These difficulties can be
avoided only by stipulation.
Consider, for instance, the question of the creator's proper
domain. Many philosophers and theologians take the creator's proper
domain to be the entirety of time and space, and furthermore hold
that issues of moral value figure ultimately in any theory of
creation. If this is so then the finitude of human scientific
observation may lead us to infer mistakenly that an organic design
(e.g., the panda's pseudothumb) is imperfect, when its imperfection
is only apparent, that is, local. On this view, any judgment of
perfection or imperfection must be qualified with a proviso that
perfection -- defined as divinely created perfection -- can be
judged only on the scale of the whole creation. And there is no
reason for a creator to optimize one part of the universe at the
expense of the whole.
As one commentator writes:
According to this view, what appears to be evil, when seen
in isolation or in a too limited context, is a necessary element
in a universe which, viewed as a totality, is wholly good. From
the viewpoint of God, who sees timelessly and as a whole the
entire moving panorama of created history, the universe is good....[27]
Several philosophers have articulated theodicies which employ
just such an analysis; Augustine and Leibniz are notable examples.
[28] In his Theodicy, Leibniz argued:
[W]e acknowledge...that God does all the best possible, in
accordance with the infinite wisdom which guides his actions...But
when we see some broken bone, some piece of animal's flesh, some
sprig of a plant, there appears to be nothing but confusion,
unless an excellent anatomist observe it: and even he would recognize
nothing therein if he had not seen like pieces attached to their
whole. It is the same with the government of God: that which
we have been able to see hitherto is not a large enough piece
for recognition of the beauty and order of the whole. [29]
Although one may regard such a theodicy with skepticism (or
scorn: see Candide), the problem remains. How is one to
judge divine perfection? The question cannot be evaded, for the
argument itself demands an answer. To be sure, one can stipulate
that only matters of biological optimality are relevant. The stipulation,
however, is entirely arbitrary.
My intention here should not be mistaken. I am not defending
a Leibnizian theodicy, but want only to stress that the "wise
creator" of the argument from divine wisdom is hardly the
plain and readily employed concept many take it to be. That these
problems have been largely ignored by exponents of the argument
should not be taken as evidence that they are insignificant.
Premise 3. "Organic design p is not perfect (or exhibits
imperfections)."
All exponents of the argument from divine wisdom hold (either
explicitly or implicitly) that perfection and imperfection are
observable aspects of organic design. Gould writes of perfection
as "the complex and perfected adaptations of organisms to
their environments: the butterfly passing for a dead leaf, the
bittern for a branch, the superb engineering of a gull aloft or
a tuna in the sea." [30]
These admirable organic designs are contrasted by Gould with
the imperfection of "[r]emnants of the past that don't make
sense in present terms -- the useless, the odd, the peculiar,
the incongruous." [31]
The terms "perfection" and "imperfection"
have long been part of the descriptive vocabulary of natural history.
We readily apply both to organic designs we admire or find puzzling
(or repugnant). As a consequence many authors use the terms with
little apparent reflection, perhaps thinking that, as operational
constructs in biology, "perfection" and "imperfection"
are entirely perspicuous. They are not. The epistemological difficulties
that plague optimality arguments in evolutionary theory also occur
in judgments of perfection (or imperfection). [32] In the latter
case, however, the difficulty of determining whether a state of
a trait or organism is optimal is magnified immeasurably by the
theological context.
Recall that the second premise of the argument states that
a "wise creator" will create perfect organic designs.
This seems clear enough until we come to particular cases, such
as the panda. Gould argues that we can use optimality theory to
designate "ideals for assessing natural departures."
[33] It follows that in finding existing pandas to be imperfect,
Gould must have some notion of an ideal panda, departure from
which evokes a judgment of imperfection. So what does an ideal
panda look like?
That is rather hard to say, as Maynard Smith has pointed out:
It is clearly impossible to say what is the "best"
phenotype unless one knows the range of possibilities. If there
were no constraints on what is possible, the best phenotype would
live for ever, would be impregnable to predators, would lay eggs
at an infinite rate, and so on. It is therefore necessary to
specify the set of possible phenotypes, or in some other way
describe the limits on what can evolve. [34]
With the argument from divine wisdom, however, the question
is not what can possibly evolve, but what can possibly be created.
If we employ the conventional conception of the creator, there
seem to be no limits on what is possible, nor any reason (short
perhaps of logical contradiction) why one hypothetically possible
panda should be preferred -- as a counterfactual ideal -- to another.
If "perfection" is limited only by the extent of one's
imagination, then specifying an ideal phenotype, for the panda
or any other organism, quickly becomes a fanciful exercise. Why
couldn't the creator have given pandas the ability to fly?
We might then turn the problem around, and define a criterion
of optimality that a "wise creator" ought to be able
to achieve. Real organisms, if they were specially created, should
then measure up. The problem we hoped to escape, however, now
returns in another form. Just as within evolutionary theory, "a
proper optimization theory must be capable of explaining why particular
constraints on [phenotypic] accessibility are regarded as absolute
while others are not," [35] so the imperfection argument
requires some intrinsic reasons why the creator's designs should
be limited by physical or biological constraints in certain instances
but not in others.
Take Gould's judgment that the panda's pseudothumb is suboptimal
or imperfect, falling short of what we might expect of a "wise
creator." Despite this judgment -- that the thumb is "somewhat
clumsy" and "wins no prizes in an engineer's derby"
[36] -- Gould writes that while watching pandas at the National
Zoo in Washington, D.C., he was "amazed at their dexterity,
and wondered how the scion of a stock adapted for running could
use its hands so adroitly." [37] Other observers of the panda
heap praise on its use of its forelimbs:
The panda can handle bamboo stems with great precision, by
holding them as if with forceps in the hairless groove connecting
the pad of the first digit and pseudothumb. [38]
When watching a panda eat leaves...we were always impressed
by its dexterity. Forepaws and mouth work together with great
precision, with great economy of motion....[39]
Although the panda's thumb may be suboptimal for many tasks
(such as typing), it does seem suited for what appears to be its
usual function, stripping bamboo. (At any rate the facts of the
matter are very much in dispute.)
But even if the pseudothumb were suboptimal for stripping bamboo,
it might still be the best structure possible. The creator could
have been limited in some way by unknown "compossibility"
constraints. In crudest outline, a compossibility analysis would
ask whether all possibilities are mutually consistent. One cannot,
for instance, expect an electric clock designed to obtain its
regularity from alternating current to be more regular than that
current. [40] Or the thumb may have some unknown primary function
for which it was designed, and the panda has co-opted it secondarily
to strip bamboo. One may have failed to identify the correct reference
situation by which to judge the design (perhaps by looking at
too narrow a slice of the panda's life history). The flippers
of marine turtles, for example, strike us as rather badly designed
for digging holes in beach sand to place eggs. The same flippers,
however, perform efficiently in the water, where the turtles spend
most of their time. Which reference situation takes precedence
in an optimality analysis? [41]
If we allow that the creator need only "act reasonably,"
that is, create organic designs which meet some specific criteria
for optimality, then we must be able to say what those criteria
are, and why they obtain, if our claims of suboptimality or imperfection
are to have any evidential force. This problem is made acute by
the bothersome truth that any suboptimal design can be made optimal
if specify the right constraints. [42] What principles, then,
guide us in specifying reasonable criteria of optimality for an
omnipotent creator?
A simple equation illustrates the problem. Suppose we define
an optimal organism (design) as scoring 1.0, where the observed
and expected design values in the following equation correspond
exactly:
observed design
expected design = optimality (suboptimality) measure expected design
Now suboptimality enters in when the numerator value falls
below that of the denominator. Thus, if an optimal (created or
ideal) panda has an expected design value of, say, 50, but actual
pandas score 30, the panda as a species is suboptimal, suffering
what we might call a "design shortfall":
observed design 30
expected design 50 = design shortfall (.4)
We cannot solve this equation, however, without the expected
design value. Absent the denominator, the equation has two unknowns
and thus is unsolvable. [43] But the expected design must be determined
by optimality criteria, a set of metrics along which design is
measured -- and we have no such metrics for living things as divinely
created. Thus we have no principled way of assigning the expected
design value.
Evolutionists have learned to be wary of facile arguments about
optimality and perfection within evolutionary theory. The divergence
of views on the panda's pseudothumb, given above, is a good example
of why they are wary. Gould finds the structure "somewhat
clumsy," whereas Schaller et al. give it the precision of
a "forceps." Would these investigators would differ
so widely on the question of, say, the panda's diploid karyotype
number?
In summary, the imperfection argument is deeply flawed. Gould
repeatedly uses the word "proof" for the argument. That,
it surely is not.
The Homology Argument
On opening any moderately advanced biology textbook nowadays
one is likely to find, amid the discussion of the evidence for
common descent, an illustration showing an array of tetrapod forelimbs.
The text will state that the pattern of similarity abstracted
from the limbs (the pentadactyl limb) can be explained only by
common descent. Francisco Ayala, for instance, is his Encyclopedia
Britannica article on evolution writes:
From a purely practical point of view, it is incomprehensible
that a turtle should swim, a horse run, a person write, and a
bird or bat fly with structures built of the same bones. An engineer
could design better limbs in each case. But if it is accepted
that all of these skeletons inherited their structures from a
common ancestor and became modified only as they adapted to different
ways of life, the similarity of their structures makes sense.
[44]
"An engineer could design better limbs in each case"
has the ring of an empirical finding. But the story is rather
more complicated.
In Chapter XIII of the Origin, Darwin argued that it
would be "hopeless" to explain the pentadactyl pattern
"by utility or by the doctrine of final causes." [45].
As Cain observes, Darwin's view of these patterns is now canonical:
Darwin...originated the evolutionary interpretation which
has been followed ever since, that the general plan of the pentadactyl
limb is not now adaptive, although it must have been in the common
ancestor, but its modifications are adaptive. [46]
But how do we know that the general plan is suboptimal? This
claim, after all, drives the inference to descent, or, to put
it another way, makes implausible the inference to an optimizing
designer. (A designer may have used the same pattern in different
organisms precisely because that pattern is optimal for the functions
in question.) What, then, grounds this seemingly empirical determination
of suboptimality?
Here a brief historical excursus will be helpful. The patterns
of homology employed by Darwin were familiar to pre-Darwinian
anatomists, having been worked out by them in a non-evolutionary
context. "Pre-Darwinian systematics did not profess an evolutionary
explanation for homology," writes Ronald Brady, "but
that privation did not prevent an extensive investigation of comparative
anatomy, during which the principles of systematics were developed."
[47] Although the "unity of plan" of the tetrapod forelimb
was powerfully suggestive of descent, and was so seen by some
pre-Darwinians, descent was far from being the only plausible
causal account available. [48] The patterns of similarity evident
among major groups of animals suggested similar functional requirements
(Cuvier), non-material archetypes (Owen), or the plan of the Creator
(Agassiz). Without transitional forms or a mechanism of functional
transformation, non-material causes were genuinely competing explanations.
[49]
Darwin made the patterns themselves the puzzle. Common descent
would become the only reasonable explanation if Darwin's readers
could be persuaded that, even without other "facts or arguments"
[50] for descent, the theory explained patterns before which rival
theories stood silent. But the rival theories -- in particular,
creation -- must in fact stand silent, for if they also explained
the patterns at hand, descent might remain only a plausible but
uncompelling theory, unable to claim broader explanatory promise
than its rivals.
In the Origin (especially Chapter XIII), therefore,
Darwin frames the patterns of comparative natural history in terms
favorable to common descent, but uncongenial to any non-material
explanation invoking design. In particular, one important avenue
of explanation open to the creationist must be cut off, namely,
the possibility that homologous patterns, such as the pentadactyl
limb, are functionally optimal, and thus, could reasonably have
been intended, and realized, by an optimizing creator.
For this task, Darwin finds a ready if unwitting ally in Owen.
"What could be more curious," asks Darwin, "than
that the hand of a man, formed for grasping, that of a mole for
digging, the leg of the horse, the paddle of the porpoise, and
the wing of the bat, should all be constructed on the same pattern,
and should include the same bones, in the same relative positions?"
[51] Four of the five examples given -- human hand, mole, horse,
and bat -- are Owen's, from On the Nature of Limbs. (Darwin
substitutes a more familiar creature, the porpoise, for Owen's
example of an aquatic mammal, the dugong.) It would be "hopeless,"
Darwin warns, to explain this pattern of similarity by functional
utility: "The hopelessness of the attempt has been expressly
admitted by Owen in his most interesting work on the 'Nature of
Limbs'." [52]
Now it appears from Darwin's phrasing ("expressly admitted")
that Owen, having failed to show that the pentadactyl pattern
was functionally useful, was conceding as much. But this is "seriously
misleading in one respect," Cain notes. "The hopelessness
of the attempt is not what Owen was driven by the facts to admit,
but what his whole lecture set out enthusiastically to proclaim."
[53] Owen was keen to refute the notion that the structures of
organisms were specifically designed for their functions. He thus
makes room for his "legitimate fruit of inductive research,"
namely, the "higher law of archetypal conformity." [54]
In attacking the principle of specific design, and arguing for
the constraints of archetypal homology, Owen cannot help supporting
Darwin -- who understandably then calls on him as an anatomical
authority favoring descent, Owen's qualms about that the naturalistic
version of that theory notwithstanding.
One will search On the Nature of Limbs in vain, however,
for anything resembling an empirical demonstration that an homologous
plan limits functionality, thus rendering an organism suboptimal.
Owen's argument rests, rather, on an a priori principle:
The teleologist would rather expect to find the same direct
and purposive adaptation of the limb to its office as in the
machine [devised by humans]. [55]
Given some functional end, the human engineer "does not
fetter himself by the trammels of any common type," says
Owen, but uses whatever design is best suited:
There is no community of plan or structure between the boat
and the balloon, between Stephenson's locomotive engine and Brunel's
tunneling machinery: a very remote analogy, if any, can be traced
between the instruments devised by man to travel in the air and
on the sea, through the earth or along its surface. [56]
Yet when we consider organismal structures, Owen argues, a
remarkable "unity of plan" is found -- "so little
to be expected, a priori":
That every segment and almost every bone which is present
in the human hand and arm should exist in the fin of the whale,
solely because it is assumed that they were required in such
number and collocation for the support and movements of that
undivided and inflexible paddle, squares...little with our
idea of the simplest mode of effecting the purpose.... [57]
Richard Owen would have designed organisms differently. But
of what evidential significance are Richard Owen's ideas about
"the simplest mode of effecting the purpose"? We want
to know if the structures of animals are well-suited to the functions
they must perform: a question to be answered -- if it can be answered
at all -- on the grounds, not of any "deep and pregnant"
a priori principle, but by observation and experiment.
Owen never demonstrates that the various mammalian forelimbs
he has examined, constructed on a common plan, are functionally
less than optimal for being so constructed. Yet this is what Darwin
takes away from Owen, and that, in turn, evolutionary biologists
have taken away from Darwin. "An engineer could design better
limbs in each case." [58] There is no evidence that this
is true.
What does ground the perception of suboptimality so widely
shared among evolutionary biologists? Here, I would argue, strong
theological preconceptions are at work. If we suppose that the
creator is free to do as he pleases, the appearance of plan can
readily become the appearance of limitation or constraint, suggesting
an unimaginative or even slavish repetition of structures along
the lines of some predetermined pattern. "Intelligence and
purpose," writes Neal Gillespie, interpreting Darwin's arguments
against creation, "should be more creative than nature showed
itself to be." [59]
The theological premise in this argument -- that the apparent
uniformity of certain biological patterns is inconsistent with
the freedom of a creator to act as he wishes -- is nowhere better
illustrated than in Darwin's book on the "contrivances"
of orchids. After reviewing the homologies of orchids and ordinary
flowers, Darwin appeals to our intuitions about what God would
have done in this case:
Can we feel satisfied by saying that each Orchid was created,
exactly as we now see it, on a certain "ideal type:"
that the omnipotent Creator, having fixed on one plan for the
whole Order, did not depart from this plan: that he, therefore,
made the same organ to perform diverse functions -- often of
trifling importance compared with their proper function -- converted
other organs into mere purposeless rudiments, and arranged all
as if they had to stand separate, and then made them cohere?
Is it not a more simple and intelligible view that all the Orchideae
owe what they have in common, to descent from some monocotyledonous
plant....? [60]
Removing the theology from Darwin's argument for the common
descent of the Orchideae would eviscerate it. Darwin provides
no fossil evidence that orchids evolved from ordinary flowers,
nor indeed any experimental evidence that such a transformation
is even possible. [61] Rather, in the chapter leading to the passage
cited above, Darwin describes patterns of similarity among orchids
-- which patterns might, on a creationist reading of the evidence,
indicate the purposeful workings of a designer. If one accepts
however the premise that it is unfitting to ascribe variations
on an "ideal type" to the direct artifice of an omnipotent
creator, the same patterns become evidence of common descent.
The theology in the passage is thus far more than a rhetorical
device. It is the logical pivot of Darwin's entire argument.
Interestingly, Gould and other commentators (e.g., Michael
Ghiselin [62]) have not noticed this problem. Perhaps Darwin's
theological aesthetic is so closely congruent with their own intuitions
that its role in the argument escapes comment. Nevertheless, these
theological assumptions are critical to the conclusions Darwin
hopes to draw from his botanical comparisons, as can be seen by
inserting different assumptions into the argument. Why not suppose,
for instance, that a divine artificer would have used homologies
between flowers and orchids? In analyzing Darwin's argument about
homologies -- in particular, his claim that a Creator would not
use such patterns -- Lovtrup observes:
Why not? Even the Creator may use a good device more than
once. Yes, why not indeed? Darwin's arguments against this possibility
are postulates, unfounded by any evidence. [63]
Different theological postulates (i.e., other than Darwin's)
would imperil his case for the common descent of the orchids.
One can jettison the theology, but then the patterns of similarity
remain only phenomena to be explained: they do not speak univocally
for descent, as opposed to design or creation.
The Influence of Darwinian Theological Metaphysics
Darwin's argument for descent with modification was pressed
on many fronts -- among them, the theological. As several historical
and philosophical analyses of Darwin's corpus have noted, [64]
the Notebooks, the Sketches of 1842 and 1844, and the Origin itself
are permeated by a metaphysical program which was, Cornell argues,
"more than useful rhetoric to Darwin, and more than a methodological
convention that promoted science." [65]
Consider one important aspect of that program, the notion of
"perfection." Dov Ospovat writes:
The assumption of perfect adaptation, which Darwin shared
with most of the biologists of his generation, was derived from
the belief that nature is a created, harmonious, and purposeful
whole....This is the assumption...that organisms are as well
fitted as possible for the conditions under which they live.
This assumption, in one form or another, was held by virtually
every naturalist and natural theologian of the mid-nineteenth
century. It is a natural, perhaps necessary, corollary of the
belief that nature is a harmonious system preplanned in every
detail by a wise and benevolent God. [66]
Cornell concurs:
The word "perfect" is an adjective generally reserved
for divine action. That is how, for instance, Paley used it,
and it was probably what Darwin understood, even when he was
criticizing the belief in the Perfection of particular forms...because
that belief implied special creation by God. [67]
Now, while Darwin came to reject the idea that organisms were
perfectly designed for their environments, he never rejected the
theoretical apparatus implied by the very terms "perfection"
and "imperfection." The numerous theological arguments
in the Origin make sense only if one presupposes certain
premises, about the Nature of the creator, from the classical
argument from design. Darwin does not challenge the orthodox (or,
in my term, conventional) conception of the creator, defended
by his creationist opponents. Rather, he turns to certain aspects
of organic design which appear to fit only awkwardly into the
usual schemes of natural theology, and drives these organic counterexamples
back into the machinery of the argument from design. Instead of
impiously attacking the nature or existence of the creator (as
a skeptic might do), Darwin offers his theory of descent (and
secondary causes) to explain what would otherwise be intolerable
anomalies. All this incongruity of design could not have been
directly created.
In so doing, of course, Darwin impales his creationist opponents
on the horns of a dilemma. Either they deny the benevolence and
wisdom of the creator, by making him the author of "abhorrent"
designs, or they retain their wise and benevolent conception of
the creator, but must greatly circumscribe his actions, for if
imperfect designs could be due to secondary causes, then could
not many other (in fact, nearly all) organic structures be the
products of secondary causes as well?
But note again that in all this there is little to indicate
that Darwin ever rejected the deep presuppositions which he inherited
from English natural theology, namely, perfection as an observable
quality of organic design, and the orthodox or conventional conception
of the nature (if not the actions) of the creator. Indeed, a close
reading of the Notebooks would seem to suggest that Darwin saw
his theory as providing a more sublime conception of the actions
of the creator (see, for instance, D 36: "What a magnificent
view one can take of the world..."). Many passages in Darwin's
corpus make little sense unless it is acknowledged that Darwin
was employing a particular conception of the creator to judge
the theories of his creative activity. Otherwise, why should the
multiple creations scornfully derided in D 36 as a "long
succession of vile molluscous animals" be beneath the "dignity"
of God?
Cornell argues, of this and other passages from later notebooks:
As always, Darwin's idea of "perfection" refers
to the nice relationship of organisms to their physical surroundings.
But it also refers to the overall design of the world, from a
divine viewpoint....Darwin's sense of a comprehensive system,
the invocation of divine perfection, and his new theory are thus
all closely related. [68]
Brooke argues, in relation to these passages:
The fact is that there are several entries in the transmutation
notebooks which indicate that Darwin was discovering a philosophy
of nature which he genuinely believed conferred a new grandeur
on the deity, despite -- or rather because of -- the fact that
it superseded Paley. [69]
While current evolutionists may not share (or in fact may be
opposed to) Darwin's theological motivations, their use of the
imperfection and homology arguments for descent presupposes the
intelligibility of notions rooted in Darwin's theological metaphysics.
The notion of perfection as an observable quality of organic design,
and the intuition lying at the heart of Darwin's metaphysics --
that a rational and benevolent God would have created an organic
world different from the one we observe -- continue to inform
the philosophical foundations of evolutionary theory (as should
be evident from the passages I have cited from Gould above).
Yet it is widely held that an important aspect of the Darwinian
revolution was the surrender, by biologists and natural historians,
of any warrant to theological speculation in science. [70] Indeed,
many scientists and philosophers would argue that natural science
and theology view each other across a largely (if not completely)
impassable epistemological gulf. [71] Science, on this view, is
by its very nature committed to a thoroughgoing methodological
naturalism. Hence, the problem which opened this essay: the persistence
of Darwinian theological themata in current evolutionary theory
is prima facie inconsistent with the doctrine of methodological
naturalism.
Now, one might argue that the thrust of my essay supports the
wisdom of the rule of methodological naturalism. "Get theology
out of science" could be the take-home moral: theists, deists,
agnostics, skeptics and atheists can all agree how to count fruit
fly bristles, say, or how to calculate the distance to the sun.
We cannot agree, even in principle (so the argument would run),
on whether God would, or would not, create vertebrates according
to homologous patterns; indeed it seems we cannot agree on anything
God would have done. "No man hath seen God at any time."
Obviously this creates problems for an empirical enterprise like
natural science.
But nothing in what I have argued should be seen as a brief
for methodological naturalism. It is possible that an intelligence
created the world, just as it is possible that, to take the other
(opposing) ancient hypothesis, the world contains its springs
of order and design wholly within itself. Whatever philosophy
of science we adopt should allow for both possibilities; methodological
naturalism does not; therefore methodological naturalism is unsound.
The interaction of science and theology is difficult. That
much should be plain. All the difference in the world exists,
however, between a rational inquiry that is difficult and one
that is in principle impossible. Unfortunately, evolutionary biologists
stand in a confused tradition with regard to these questions.
On one hand, as Ernst Mayr points out, Darwin himself was converted
to his new ideas only after he had made numerous observations
that were to him quite incompatible with creation. He felt strongly
that he must establish this point decisively before his readers
would be willing to listen to the evolutionary interpretation.
Again and again, he describes phenomena that do not fit the creation
theory. [72]
That the phenomena do not fit the creation theory implies of
course that they might have fit. As it happens, they did not,
and thus the theory of creation in question is false. It is, I
think, impossible to understand "the long argument"
of the Origin except in this light. Darwin was testing
a theory of creation -- a process methodological naturalism holds
to be in principle impossible. This historical evidence about
the actual practice of science suggests that descriptively, at
any rate, the thesis of methodological naturalism is going to
fail badly.
On the other hand, Darwin also argued that theories of creation merely restate
the facts to be explained "in dignified language," implying that such
theories were sham explanations, saying nothing about the phenomena beyond "we
can only say that so it is; -- that is has so pleased the Creator to construct
each plant and animal." [73] And in later editions of the Origin,
as David Hull points out, Darwin concluded his discussion of Owen's interpretation
of homology by arguing "but this is not a scientific explanation."
[74] On this view of the Darwinian Revolution, one for which there is powerful
evidence, Darwin had the same opinion of all [theories of origin] but his own
-- they were not 'scientific'....The Darwin revolution was as much concerned
with the promotion of a particular view of science as it was with the introduction
of a theory on the transmutation of species. [75]
Proper scientific explanations employ verae causae in principle
accessible to all observers, which supernatural action manifestly
is not, and so on. [76]
Thus at the fountainhead of the dominant scientific explanation
of origins we find uncertainty about the "scientific"
status of design or creation theories. Such theories are testable
--yet they are not testable. They engage the facts by real predictions
-- yet they say nothing about the facts beyond what the facts
themselves already told us.
The cynical reading of this uncertainty (a posture endemic
throughout evolutionary theory today) looks no further than the
pragmatism of "any stick will do to beat a dog." That
is, where the religiously-motivated opponents of evolution are
concerned, we need not make too great a virtue of consistency.
Get (and keep) theology out of science, by any means necessary,
if it comes to that. Niceties about testability or empirical content
are quite beside the point. There is too much at stake.
The cynical reading, while it may be true, is almost too bleak
to bear. It implies that science is not a truth-seeking enterprise,
but something closely approximating advertising or propaganda,
where success in the competition (however that be defined) is
everything. I don't believe this -- actually, I can't bear to
believe it -- and hope the reader doesn't either. Suppose then
that we lay aside the cynical reading as too dispiriting.
The charitable reading of the uncertainty about the scientific
status of design suggests that it reflects philosophical confusion.
Somewhere in the deeper logic of our current conception of scientific
explanation, we have made, or overlooked, a very serious blunder.
Among the elements of what Gerald Holton calls "the modern
world picture" -- that is, the received scientific world
picture -- there exist profoundly inconsistent epistemological
commitments. [77] Put more simply, if what we want is the truth
about how the world and its creatures came to be, then we may
not be able to tell that story in fully naturalistic terms. Because
the truth -- to modern eyes ungainly, even ugly -- may be otherwise.
Acknowledgments
I thank Steve Meyer, Bill Dembski, Jon Wells, Jitse van der
Meer, Michael Ruse, Bill Wimsatt, Bob Richards, and Leigh Van
Valen for helpful discussions. A related version of this essay
appears as "The Role of Theology in Current Evolutionary
Reasoning," in Biology &Philosophy 11 (1996):
pp. 493-517.
Notes
1. Douglas Futuyma, Evolutionary Biology
2nd edition (Sunderland, Mass.: Sinauer Associates, 1986), 15.
By "evolution" I mean what Doolittle calls the "widely
accepted" theory that "all Life on Earth today is descended
from a common ancestral organism that existed sometime between
1.5 and 3.0 billion years ago" -- this evolution occurring
by means of the natural selection of undirected and randomly arising
variation (Russell R. Doolittle, "New Perspectives on Evolution
Provided by Protein Sequences," in New Perspectives on
Evolution, eds. L. Warren and H. Koprowski [New York: Alan
Liss, 1991], p. 165).
2. Salvador Luria, Stephen Jay Gould, and Sam
Singer, A View of Life (Menlo Park, California: Benjamin/Cummings,
1981), p. 581.
3. George Williams, Natural Selection: Domains,
Levels, and Challenges (Oxford: Oxford University Press, 1992),
pp. 72-73.
4. Bruce Alberts, "The Function of Hereditary
Materials," American Zoologist 26 (1986): 786-787.
5. See, e.g., Francisco J. Ayala and James
Valentine, Evolving: The Theory and Processes of Organic Evolution
(Menlo Park, California: Benjamin/Cummings, 1979), 5; Niles Eldredge
and Joel Cracraft, Phylogenetic Patterns and the Evolutionary
Process (New York: Columbia University Press, 1980), 3; Stanley
Beck, "Natural Science and Creationist Theology," BioScience
32 (1982), 739-740; D. Futuyma, Science on Trial, 169-170;
Anne Riddiford and David Penny, "The scientific status of
modern evolutionary theory," in Evolutionary Theory: Paths
into the Future, ed. J.W. Pollard (New York: John Wiley, 1984),
18; S.J. Gould, "Darwinism Defined: The Difference between
Fact and Theory," Discover, January 1987, 70; Antoni
Hoffman, Arguments on Evolution (Oxford: Oxford University
Press, 1989), 11-12.
6. From Phillip Johnson, Stephen Meyer, Alvin
Plantinga, Jitse van der Meer, and J.P. Moreland, among others.
7. Ernst Haeckel, The History of Creation
(New York: D. Appleton, 1876), 291.
8. See, e.g., Francois Jacob, "Evolution
as Tinkering," in The Possible and the Actual (New
York: Pantheon, 1982); Elliott Sober, The Nature of Selection
(Cambridge, Mass.: MIT Press, 1984), 175-76; Douglas Futuyma,
"Evolution as Fact and Theory," Bios 56 (1985),
6; Richard Dawkins, The Blind Watchmaker (New York: W.W.
Norton, 1986), 91-94; Richard Burian, "Why the panda provides
no comfort to the creationist," Philosophica 37 (1986),
11-25.
9. Stephen J. Gould, Ever Since Darwin
(New York: W.W. Norton, 1977), 91.
10. Stephen J. Gould, The Panda's Thumb
(New York: W.W. Norton, 1980), pp. 20-21.
11. Stephen J. Gould, Hen's Teeth and Horse's
Toes (New York: W.W. Norton, 1983), 160, 164.
12. Ibid., p. 258.
13. Stephen J. Gould, "Evolution and the
Triumph of Homology, or Why History Matters," American
Scientist 74 (1986), 63.
14. Gould, "Triumph of Homology,"
64.
15. See, for instance, Reinhard Junker and
Siegfried Scherer, Entstehung und Geschichte der Lebewesen
(Giessen: Weyel Lehrmittelverlag, 1988); Chris Darnbrough, "Genes
-- created but evolving," in Concepts in Creationism,
eds. E.H. Andrews, W. Gitt, and W.J. Ouweneel (Herts, England:
Evangelical Press, 1986), 241-266; and Hendrik Murris, "The
concept of the species and its formation," 175-207, in the
same volume.
16. Douglas Futuyma, Science on Trial
(New York: Pantheon, 1983), 198.
17. Wayne Frair and Percival Davis, A Case
for Creation (Chicago: Moody Press, 1983), 29.
18. Bruce Naylor, "Vestigial Organs are
Evidence of Evolution," Evolutionary Theory 6 (1982),
94.
19. Murris, "Concept of the species,"
200-201.
20. Junker and Scherer, Geschichte der Lebewesen,
126.
21. Reinhard Junker, Rudimentare Organe
und Atavismen: Konstructionsfehler des Lebens? (Berlin: Studium
Integrale, Zeitjournal Verlag, 1989).
22. Darnbrough, "Genes -- created but
evolving," 252-262.
23. See Mill's Three Essays on Religion, in
particular, the essay on "Theism," Part I, especially
the Introduction and chapter 6, and Part II, "Attributes."
Bertrand Russell discusses a similar conception of the creator:
"He need not be omnipotent or omniscient; He may be only
vastly wiser and more powerful than we are. The evils in the world
may be due to his limited power. Some theologians have made use
of these possibilities in forming their conception of God"
(History of Western Philosophy, New York: Simon & Schuster,
1945; 589).
24. Gould, "Panda's thumb," 28.
25. Thanks for Frank Arduini for this phrase.
26. Hume's Dialogues Concerning Natural Religion,
especially Part V, is the classical expression of the difficulties
that follow from considering the full range of logically possible
supreme beings (creators).
27. John Hick, "Evil, The Problem of,"
in The Encyclopedia of Philosophy, ed. Paul Edwards (1967),
137.
28. See Augustine, On Order.
29. G.W. Leibniz, Theodicy (La Salle,
Illinois: Open Court, [1710], 1985), 206-207.
30. Gould, Panda's Thumb, 28, emphasis added.
31. Ibid., 28-29.
32. The literature on optimality theory and
its difficulties is very extensive. The "epistemological
difficulties" I have in mind are best explained by Richard
Lewontin, in his essay "The Shape of Optimality," in
The Latest on the Best, ed. John Dupre (Cambridge, Mass.:
MIT Press, 1987), pp. 151-59.
33. Gould, "Triumph of Homology,"
66.
34. John Maynard Smith, "Optimization
Theory in Evolution," Annual Review of Ecology and Systematics
9 (1978), 32. Under the heading, "What is possible?,"
R. McNeill Alexander takes up the same question. "The next
problem, after deciding what is likely to be optimized, is to
decide what structures or strategies are possible, and what constraints
apply. If no such limitations were recognized it would have to
be concluded that optimum structure would make bones unbreakable
and without mass, and an optimum life-history would involve immortality
and infinite fecundity" (Optima for Animals [London:
Edward Arnold, 1982], 97).
35. Lewontin, "The Shape of Optimality,"
156.
36. Gould, Panda's Thumb, 24.
37. Ibid., 21.
38. George Schaller, H. Jinchu, P. Wenshi,
and Z. Jing, The Giant Pandas of Wolong (Chicago: University
of Chicago Press, 1986), 4; emphasis added.
39. Ibid., 58; emphasis added.
40. See Nicholas Rescher, Leibniz: An Introduction
to his Philosophy (Oxford: Basil Blackwell, 1979), chapter
VI, for an explication of such compossibility arguments within
Leibniz's philosophy.
41. Richard C. Lewontin, "Adaptation,"
in Conceptual Issues in Evolutionary Biology, ed. Elliott
Sober (Cambridge, Mass.: MIT Press, 1984), 234-251.
42. Lewontin, "Shape of Optimality,"
158-59.
43. Gabriel Nelson kindly pointed this out
to me.
44. Francisco J. Ayala, "Evolution, The
Theory of," Encyclopedia Britannica, 15th ed. (Chicago: Encyclopedia
Britannica, 1988), 987, emphasis added.
45. Darwin, Origin of Species, 435.
46. A.J. Cain, "The perfection of animals,"
in Viewpoints in Biology, Volume 3, eds. J.D. Carthy and
C.L. Duddington (London: Butterworths, 1964), 44.
47. Ronald Brady, "On the Independence
of Systematics," Cladistics 1: 113-126; p. 114.
48. E.S. Russell, Form and Function
(Chicago: University of Chicago Press, 1982 [1916]), p. 214.
49. Olivier Rieppel, Fundamentals of Comparative
Biology (Basel: Birkhauser Verlag, 1988), pp. 49-51.
50. Darwin, Origin of Species, p. 458.
51. Ibid., p. 434.
52. Ibid., p. 435.
53. Cain, "Perfection of animals,"
p. 44.
54. Richard Owen, On the Nature of Limbs
(London: John Van Voorst, 1849), p. 70.
55. Ibid., p. 10.
56. Ibid.
57. Ibid., p. 40; emphasis added.
58. Ayala, "Evolution, The Theory of,"
p. 987.
59. Neal Gillespie, Charles Darwin and the
Problem of Creation (Chicago: University of Chicago Press,
1979), p. 71.
60. Charles Darwin, On the Various Contrivances
by Which Orchids Are Fertilized by Insects (Chicago: University
of Chicago Press, [1877] 1984), pp. 245-46.
61. Darwin performed numerous experiments (the
description of which constitutes much of the book) to understand
the functional aspects of orchid fertilization. In the last chapter,
he draws this moral from the experiments: "No one who has
not studied Orchids would have suspected that these and very many
other small details of structure were of the highest importance
to each species; and that consequently, if the species were exposed
to new conditions of life, and the structure of the several parts
varied ever so little, the smallest details of structure might
readily be acquired through natural selection. These cases afford
a good lesson of caution with respect to the importance of apparently
trifling particulars of structure in other organic beings"
(Various Contrivances, p. 287).
62. See Michael Ghiselin, The Triumph of
the Darwinian Method, 2nd edition, Chicago: University of
Chicago Press, 1984.
63. Soren Lovtrup, Darwinism, The Refutation
of a Myth (London: Croom Helm, 1987), p. 132.
64. See, e.g., Gillespie, Charles Darwin
and the Problem of Creation, J.H. Brooke, "The Relations
Between Darwin's Science and his Religion," in Darwinism
and Divinity, ed. J. Durant (London: Basil Blackwell, 1985),
pp. 40-75, and Cornell, "God's Magnificent Law."
65. Cornell, "God's Magnificent Law,"
pp. 384-385.
66. Dov Ospovat, "God and Natural Selection:
The Darwinian Idea of Design," Journal of the History
of Biology 13 (1980), pp. 189-190.
67. Cornell, "God's Magnificent Law,"
p. 396.
68. Ibid., p. 397.
69. Brooke, "Relation between Darwin's
Science and his Religion," p. 46.
70. Mayr, "Darwin, intellectual revolutionary,"
p. 25.
71. The literature on this question is vast;
for a representative selection of opinion, see Leszek Kolakowski,
_Religion_ (Oxford: Oxford University Press, 1982); Langdon Gilkey,
Creationism on Trial (Minneapolis: Winston Press, 1985);
Keith Yandell, "Protestant Theology and Natural Science in
the Twentieth Century," in God and Nature, eds. D.C.
Lindberg and R.L. Numbers (Berkeley: University of California
Press, 1986), pp. 448-471; and Stephen J. Gould, "Darwinism
Defined," p. 70.
72. Ernst Mayr, Introduction to the facsimile
reprint of the Origin of Species (Cambridge, Mass.: Harvard
University Press, 1964), p. xii.
73. Charles Darwin, On the Origin of Species
(Cambridge, Massachusetts: Harvard University Press, 1964 [facsimile
reprint of 1st edition]), 186, 435.
74. David L. Hull, "Darwin and the nature
of science," in Evolution from Molecules to Men (Cambridge:
Cambridge University Press, 1983), D.S. Bendall, ed., 71.
75. Ibid., 64-65.
76. Jonathan Hodge has led among Darwin scholars
in interpreting this aspect of Darwin's scientific outlook: "The
epistemological rationale for [Lyell's] presumption, of the persistence
of all . . . causes of change into the present and future, is
the ideal of explanation by real or existing causes, verae causae.
Like his friend (and the undergraduate Darwin's scientific hero)
the physicist John Herschel (1792-1871), Lyell followed earlier
writers, most notably the Scottish philosopher Thomas Reid (1710-1796),
who had drawn this moral from the superior evidential credentials
of the Newtonian gravitational force over the Cartesian ethereal
vortices: any causes invoked in an explanatory theory should,
ideally, be known to exist through direct observation independently
of the facts they are supposed to explain. . . . Such, then, was
the context, at once systematic and epistemological wherein Darwin,
from 1834 on, was theorizing about species extinctions and origins"
("The development of Darwin's general biological theorizing,"
in Evolution from Molecules to Man ed. D.S. Bendall [Cambridge:
Cambridge University Press, 1983], 45-46).
77. The "items characterizing a modern
world picture," Holton argues, include a "high place
for 'objectivity'," a "proof-oriented" outlook,
"demanding verification or test of falsification," "skepticism
with respect to authority," and an "avowedly secular,
anti-metaphysical" standpoint (Gerald Holton, Science
and Anti-Science [Cambridge, Mass.: Harvard University Press,
1993], 173-74). The philosophical confusion reading of the uncertainty
about the scientific status of design suggests that if design
is true, the "avowedly secular" element of the modern
world picture is mistaken -- and whether design is true cannot
be settled by appealing to the "avowedly secular" element
of the modern world picture, without begging the question.
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