Christian philosophers Del Ratzsch and Alvin Plantinga propose a different way of thinking about the evidence for design in biology. They contend that we sometimes can perceive or recognize design directly, without having to infer it as the conclusion of an argument. This claim is not as incredible as it may seem at first blush. Many ordinary beliefs are formed by perception or recognition rather than by making inferences. When I recognize my wife’s voice on the phone, for example, I immediately form the belief that she is the one speaking to me; I don’t have to engage in any inferential reasoning to arrive at that conclusion. There is nothing irrational (or unreasonable) about my belief, moreover, even though I have no argument for it. I can’t describe my wife’s distinctive vocal qualities in a way that would enable someone else to recognize her voice on the phone, so I can’t explain how I know it is her voice; yet, somehow, I really do know it is hers. My belief that she is speaking to me is well-justified because it is strongly supported by a kind of perceptual evidence, although I cannot present that evidence in an argument. (I can’t even say precisely what the evidence is!) Similarly, Ratzsch and Plantinga suggest, we are able to perceive design in nature, thereby forming a reasonable (or justified) belief that we are seeing something designed, even if we cannot say precisely how we recognize it as such.Alvin Plantinga, Where the Conflict Really Lies: Science, Religion, and Naturalism (New York: Oxford University Press, 2011), Chapter 8, especially pp. 236-259; and Del Ratzsch, “Perceiving Design,” in Neil A. Manson (ed.), God and Design: The Teleological Argument and Modern Science. (New York: Routledge, 2003), 124-143.
Of course, perceptions are fallible. Other evidence might give us reasons to abandon a belief that was based on perception, or to avoid forming the belief in the first place. This can happen in two ways. First, we might acquire independent evidence for the falsity of the perception-based belief. For instance, if I think I recognize my wife’s voice on the phone but then notice that she is quietly standing nearby, I will conclude that my perception of her voice was mistaken. Evidence like that is called a rebutting defeater for the perception. Second, we might learn something that undercuts our trust in the perceptual evidence itself. For example, if I discover that my daughters sound uncannily similar to my wife on the phone, I will have reason to doubt that I can reliably distinguish my wife’s voice from theirs. Evidence that makes it unreasonable to trust a perception (without providing independent evidence against the perception-based belief) is called an undercutting defeater for the perception.
Is the evidence for evolution either a rebutting defeater or an undercutting defeater for perceptions of design in biology, making it unreasonable for us to trust those perceptions? Plantinga argues that evolutionary biology cannot be a rebutting defeater—that is, it cannot show that living things were not designed—because evolution is compatible with some design hypotheses. Even if we have a complete evolutionary explanation for all features of the human eye, for example, this wouldn’t show that the eye wasn’t designed. God might have designed the human eye via evolutionary processes: he might have caused specific mutations to occur at just the right times in evolutionary history, and he may have superintended environmental conditions so that natural selection would favor organisms with the ocular features he planned, and so on. Several other design hypotheses are also compatible with evolutionary explanations, as we’ll see on the next page.
On the other hand, Plantinga says, evolutionary explanations do give us reasons to reduce our confidence in some perceptions of design. Insofar as the theory of evolution makes it plausible that eyes and other seemingly-designed structures could have arisen without a designer, they cast doubt on the reliability of design perception: some cases in which we think we recognize design might not be instances of design after all. This doubt does not undercut our perceptual evidence completely, however. Even when we are unsure whether a perception of design is veridical, the perception still constitutes evidence, albeit weaker evidence than we would have had if no alternative explanation were available. In Plantinga’s words, evolutionary science gives us “a partial undercutting defeater” for perceptions of design in structures like the human eye. So, upon finding evolutionary explanations for structures like the eye, you “should somewhat reduce your conﬁdence that these structures have been designed.”Alvin Plantinga, Where the Conflict Really Lies: Science, Religion, and Naturalism (New York: Oxford University Press, 2011), 256. Emphasis in original.
Nevertheless, since the theory of evolution doesn’t completely undercut our perceptual evidence for design, we have reason to trust those perceptions to some degree, especially in cases where evolutionary explanations are unavailable or implausible. In particular, Plantinga argues, perceptions occasioned by biochemical machinery provide relatively strong evidence of design. Evolutionary science has not yet explained the origin of machines like the flagellar motor, so we have no undercutting defeaters (or we have, at most, extremely weak partial defeaters) for perceptions of design in those machines.As Plantinga observes: “For these structures at the cellular and molecular level, there aren’t (yet) any Darwinian accounts or explanations. Those ardent devotees of natural selection who proclaim that contemporary Darwinian science has completely explained the apparent design in the biological realm, and in fact thus completely explained it away, are mistaken about the entire molecular level. Here (so it seems) there isn’t a lot beyond just-so stories. If this is true, then there aren’t any defeaters, either rebutting or undercutting, for Behe design beliefs [i.e., perceptions of design in biochemistry].”
However, Plantinga later concedes that evolutionary science may provide extremely weak undercutting defeaters for perceptions of design in biochemical machines. Insofar as evolutionary explanations “at the level of gross anatomy” cast doubt on the reliability of design perception in general (see above), they may give us some reason to question design perceptions at the cellular level too: “True, there are reasonably plausible Darwinian explanations at the anatomical level for many structures and systems; that fact should perhaps reduce the conﬁdence with which one forms design beliefs at the cellular level. So we can say that here too we have a partial defeater. But (in my judgment) it is an extremely partial defeater.” Alvin Plantinga, Where the Conflict Really Lies: Science, Religion, and Naturalism (New York: Oxford University Press, 2011), 258-259. Regardless of whether Michael Behe’s argument from irreducible complexity is cogent, therefore, the appearance of design in such structures gives us undefeated perceptual evidence that they were designed:
So the real signiﬁcance of Behe’s work, as I see it, is not that he has produced incontrovertible arguments for the conclusion that these systems have been designed; it is rather that he has produced … several sets of circumstances in which design perception occurs, for which in fact there aren’t any defeaters.Alvin Plantinga, Where the Conflict Really Lies: Science, Religion, and Naturalism (New York: Oxford University Press, 2011), 258.
Whereas Behe and other ID theorists have taken the burden of proof upon themselves by constructing philosophical arguments for design, Plantinga contends that we don’t need an argument in order to be reasonable in holding the perception-based belief that some biological structures were designed. Perceptions are innocent until proven guilty, so to speak. We can reasonably trust our perceptions of design so long as we have no undercutting or rebutting defeaters for them. Since we have no defeaters for some perceptions of design in nature, according to Plantinga, the onus lies with opponents of ID to show that our perceptions of design are illusory. Critics of ID have failed to meet this challenge.
Interestingly, some evolutionary creationists who oppose the ID movement agree, nonetheless, that we can perceive design in nature. Deborah Haarsma, president of the evolutionary creationist organization BioLogos, expresses her view this way: “we can perceive design in nature even when scientists have a complete natural explanation. While ID points to supposed flaws in evolutionary explanations, EC [evolutionary creationism] sees design in the whole fabric of the universe that makes life (and evolution) possible.”Deborah B. Haarsma, “Response from Evolutionary Creation,” in J.B. Stump and Stanley N. Gundry (eds.), Four Views on Creation, Evolution, and Intelligent Design (Grand Rapids: Zondervan, 2017), 222. I don’t know whether Haarsma would concede that we can perceive design in biochemical structures like the flagellar motor, but such a view would be consistent with evolutionary creationism. Indeed, several design hypotheses are fully compatible with mainstream evolutionary theory, as we’ll see on the next page.