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The Argument from Design in Evolution
Natural theology is not bad science; it is bad theology. Biologists may likewse be wary of theological assumptions in their own arguments about the nature of evolution.

Note: This article is a counterpoint to "Teaching Darwin Seriously".

In the early 1800s many naturalists in England reveled in the "design" of nature as theological evidence of God and his wisdom. For them, science and religion were insepar-able. Such arguments provided a context for Darwin when he presented his case for evolution by natural selection. Darwin needed to explain how an organ as complex as an eye could evolve without divine foresight or guidance. He anticipated that "organs of extreme perfection" would be a chief difficulty for his doctrine of descent with modification.

Is such natural theology bad science? No, according to philosopher Paul Nelson, it is not bad science, it is bad theology. Moreover, he asserts, when scientists stake comparable claims about whether God has had a role in evolution, they too are practicing theology, not science. In particular, Nelson questions whether "senseless" structures, such as vestigial organs, can indicate that the process was independent from divine guidance. Such arguments about design are fundamentally religious, he claims, not scientific.

Nelson is a creationist, but he is not trying to leverage equal time in the classroom. Rather, he wants to clarify the domains of argument, especially by identifying the role of religious assumptions in both camps. Ultimate-ly, he argues as much against many traditional religious perspectives as he does against common scientific and educational practice.

Nelson's argument has two layers. First, he criticizes natural theology in uncompromising terms. Why? Because it presumes we can understand God's intent and how the Creator works. Such knowledge cannot possibly be available to us--mere objects of creation. As imperfect beings, how can we even begin to guess God's purpose or know what is perfect? For Nelson, natural theology is bad theology because it makes unwarranted assumptions about the Creator. "Perfect" organic structures don't reveal "purpose" and are not proof of God.

Of course, if the "design" of organisms--perfect or imperfect--cannot be unequivocal proof of God, neither can they be proof of evolution. Such evolutionary arguments have been articulated and widely promoted by Harvard paleontologist Stephen Jay Gould. Gould notes that the apparent perfection of adaptations can be explained equally well by natural selection or by special divine creation. Thus, adaptations--mimicry, distinctive dentition, light-weight feathers, etc.--cannot help us decide between the two hypotheses. Instead, Gould argues, we must look to structures that are not "perfectly" designed--structures whose form and function only make sense to us in terms of history. And like his natural theologian cousins, Gould enjoys pointing out such "odd" structures (1980a, 1980b, 1995).

Gould's hallmark example is the panda's "thumb," a short appendage with which the panda strips bamboo leaves from their stalks. But while the appendage works much like our opposable thumb, it is not a thumb; it is an extension of the radial sesamoid, a wrist bone. Gould argues that this structure is a "funny solution": a wrist bone has been remodeled for something other than its original purpose. It is not ideal engineering, as we might expect of an omniscient Designer who created each species independently. For Gould the panda's thumb is proof of a path that "a sensible God would never tread, but that a natural process, constrained by history, follows perforce" (1980a, pp.20-21). "Nature," he quotes François Jacob, "is an excellent tinkerer, not a divine artificer" (p.26). The same argument, Gould notes, applies to orchid flower structure, whale hips, and turtle breeding grounds, among others.

Nelson finds Gould argument flawed. To begin, Nelson points out that even Gould is impressed with the "elegant" functioning of the panda's thumb. If it is not an "ideal" solution, its dexterity nonetheless "amazed" Gould and, in his own words, "excites our imagination." What does it mean to say that a structure is not "ideal," if it seems to perform a function well? Where is the imperfection? Who can say that the panda's "thumb" is not perfectly designed or was not intended to work as it is currently structured?

Further, Gould's argument, like that of the natural theologians, relies on assumptions about God, what is perfect, and what is not. Gould speculates, "if God had designed a beautiful machine to reflect his wisdom and power, surely he would not have used a collection of parts generally fashioned for other purposes" (1980a, p.20). The argument may be true, but it is purely theological. Gould is reasoning about the nature of God, here, not evolution. He has inserted virtually undetected a religious assumption in his "scientific" argument. The moment that God enters an argument, Nelson notes, it has lost its purely scientific character. The panda's thumb argument, therefore, is fundamentally religious, not scientific.

Structures like the panda's thumb are suggestive of history at best. But the judgement derives from comparative anatomy, not from any actual documentation of change. Concluding that the difference is evidence of evolution requires further assumptions. Inferring adaptation through natural selection also requires interpreting design and purpose--a first step beyond the scientific realm. While the panda's thumb argument may succeed in theological terms against certain conceptions of a Creator, it cannot invalidate other conceptions of God or God's role in the natural history of organisms. Evolutionists and teachers of evolution would be well advised to rethink their arguments. Scientists tread on religious ground when they contrast natural selection to the work of a Creator and when they make assumptions about perfect or ideal design.


  • Gould, Stephen. 1980a. "The Panda's Thumb." The Panda's Thumb. New York: W.W. Norton. pp. 19-26.
  • ------. "Senseless Signs of History." The Panda's Thumb. pp. 27-34.
  • ------. 1995. "Hooking Leviathan by its Past." Dinosaur in a Haystack. New York: Harmony Books.
  • Nelson, Paul. 1996. "The Role of Theology in Current Evolutionary Reasoning." Biology and Philosophy 11:493-517.

updated: 6/20/07

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