Let’s turn now to Plantinga’s assessment of Michael Behe’s biological design arguments. Plantinga takes these ID arguments seriously, and I respect him for that. Too often theists embrace the fine tuning argument but dismiss biological ID arguments (maybe because the latter aren’t as ‘respectable’ in scientific circles). But if one accepts the former, so it seems to me, one should a fortiori accept the latter. The appearance of design is even more impressive with respect to biology than with respect to physics. Plantinga is just being consistent here. His evaluation of Behe’s argument is favorable, but modest: it provides some support for theism, but isn’t a slam dunk.
Plantinga then shifts focus from design arguments to what he calls ‘design discourse.’ This is the novel innovation in the book. It is quite natural to interpret what Behe, or his predecessor William Paley, are doing as giving an argument that some feature of the natural world is designed. These design arguments come in different forms: arguments from analogy or inference to the best explanation, for example. These approaches have their strengths and weaknesses. However, what if we interpret what Behe and Paley are doing, not as design arguments, but as design discourse? In other words, what Behe and Paley are doing is not primarily providing us with an argument from which we then infer design; rather they are putting us in a position in which we can perceive design. Plantinga, as he has before, talks about the way we form beliefs in other minds, other peoples’ mental states, the past, etc. We don’t arrive at these beliefs through an argument; we simply perceive them if our cognitive faculties are functioning properly. In a similar way, design discourse puts us in a situation in which we can perceive design in a basic way.
This perception of design is common and compelling. Dawkins admits that the living world displays the overwhelming appearance of being designed (even though he thinks it isn’t). Plantinga also quotes Francis Crick, also no friend of theism, who says: “Biologists must constantly keep in mind that what they see was not designed, but rather evolved” (p. 257). Plantinga thinks that the reason for this is that what biologists see looks for all the world as if it were designed. This perception of design is so strong that biologists must constantly remind themselves otherwise. I have to say that I’ve experienced this design perception myself. I remember seeing one of those David Attenborough nature programs about a certain type of bio-luminescent fish. Later, while on a long drive, I remember the feeling of utter incredulity that this creature could have evolved by chance. I was certainly familiar with the theory of evolution, and certainly knew what the evolutionist’s comeback would be, but I couldn’t shake the feeling. I take it that this is what Plantinga has in mind regarding the perception of design.
But let’s give the evolutionist his due: the beauty of Darwin’s theory is it’s power to explain how creatures which overwhelmingly display the appearance of design, could come about by purely blind, mechanical means. Shouldn’t this cause us to second guess our design perception, regardless of how strong it might be? Plantinga anticipates this objection. Of course, basic beliefs are not immune to defeaters. To use one of Plantinga’s examples, if I seem to see a sheep in a field, I’ve formed the belief “there is a sheep in that field” in a properly basic way. However, if you, the owner of the field, come along and tell me that there are no sheep in the field, but it’s frequented by a dog that can be mistaken for a sheep at a distance, I will have a defeater for my belief that there is a sheep in the field. Now, there are different types of defeaters. If you tell me that there are no sheep in the field, I will have a rebutting defeater for my belief; I will now believe that there are no sheep in the field. But, if you tell me there may be a sheep in the field, but there may also be a dog that is easily mistaken for a sheep, I will have an undercutting defeater. I will no longer be confident that there is a sheep in the field, but nor will I think that there isn’t a sheep in the field. Moreover, undercutting defeaters come in different strengths. For example, one might have a weak or partial undercutting defeater.
Restating our question: does the theory of evolution constitute a defeater of design beliefs formed in a basic way? And if so, is evolution a rebutting defeater or an undercutting defeater? And if the latter, is it strong or weak? Plantinga argues that evolution does constitute a defeater to design beliefs, but it is only a partial undercutting defeater (p. 256). That is to say, it should reduce our confidence in our design beliefs, but not by much. How much is ‘not much’? Plantinga thinks there is no general answer to this question. It’s hard to say how much evolution should reduce our confidence in design beliefs formed in a properly basic way, i.e. by perception. Presumably, however, Plantinga thinks it shouldn’t reduce our confidence enough to make us agnostic on the matter of whether design is present. Far from evolution being a rebutting defeater of design, as Dawkins would claim, we have at best a partial undercutting defeater.
I’m not sure I agree with Plantinga about the degree to which evolution constitutes a defeater of design beliefs. I agree that it’s not a rebutting defeater, but I suspect it’s a stronger undercutting defeater than Plantinga does. In other words, once one is aware of evolution, one has a defeater for one’s design beliefs, i.e. one should have reduced confidence in one’s belief that design is present. To revisit my above example, I see a documentary featuring a remarkable bio-luminescent fish. Upon reflecting on this creature, I’m taken with the belief that it must be designed. I can’t, in that moment, imagine how it might have come about by chance. But then I recall that Darwin and subsequent biologists have explained that much of what looks designed is perfectly explicable in terms of blind physical forces. For all I know, there is a similar explanation for the bio-luminescent fish. I therefore have a defeater for my design belief. My confidence in it is thereby reduced, I would guess by at least half. It’s an undercutting defeater insofar as I can’t say with confidence that it isn’t designed, but neither can I be confident in saying that it is designed. At best, I think we’re left with agnosticism at this stage, barring any further information. So I have to conclude that evolution is a successful defeater for my design belief in this case. Nonetheless, I think Plantinga’s introduction of design discourse is a fruitful way to think about these issues.