The question of how we detect design is a question that both atheists and theists can equally well engage in. The question comes up when one is engaged in the project of looking for scientific evidence for the existence of a supernatural God, but the question also comes up when, for example, one ponders what structures one would have to find on a planet for one to conclude that the planet is probably inhabited by intelligent aliens. 

William Dembski famously answers that, to infer design, one must find specified complexity. While I won’t try to argue this here, I share the opinion of many that his notion of specification isn’t that well worked out. Del Ratzsch agrees with Dembski that complexity isn’t enough, but Ratzsch argues that what it takes in addition to complexity is mind-affinity, as well as factors that would be relevant to the intent an agent would have to realise a particular value. (Ratzsch doesn’t have a good name for this latter sort of factor; let’s call it “value-affinity”.) 

By “mind-affinity”, Ratzsch is getting at patterns that match patterns that a mind would be expected to create. For example, if we saw “John 3:16” spelled out using rocks on the side of a mountain, we would think that that distribution of rocks was the pattern of design, not chance. With value-affinity, Ratzsch is talking about effects that an agent would want to realize in the course of realizing some value. For example, there is evidence that in the distant past there was a nuclear reaction that happened in a river, not as a product of human agency. If that reaction didn’t have any substantive effects, we would probably conclude that the reaction happened as a result of chance processes. But if that reaction was causally efficacious in producing intelligence in human ancestors, and intelligence couldn’t have been produced any other way, we would think it more probable that the reaction happened as a result of design. 

In my opinion, Ratzsch is giving a more promising answer than Dembski. Ratzsch’s discussion of mind-affinity and value-affinity on pages 61-69 of his book Nature, Design, and Science is quite brilliant. It’s disappointing that the intelligent design literature focusses on Dembski’s answer and not Ratzsch’s.

An uninformed observer who came across a Mandelbrot set would presumably think that it was the product of an intelligent designer:

But in fact, the Mandelbrot set is the product of a relatively simple mathematical equation. Ratzsch addresses this in an interesting footnote:

prior to any familiarity to their mode of generation, it might be intuitively reasonable to take Mandelbrot pictures as designed. In fact, were their structure artifactual I suspect that we would so construe them. But, of course, their structure is a result of mathematical necessity, and some would argue that necessities cannot be products of agent activity and design. (p. 185)

I take it from what Ratzsch does say that he recognizes that he doesn’t have a completely satisfying answer here. What I would (tentatively) say is that the structure (despite appearances) is not complex — it can be generated via a simple mathematical process. Ratzsch wouldn’t be happy with this complexity answer — after all, as discussed in my previous post, a titanium cube is not complex, and yet Ratzsch takes it as evidence for design — but the complexity answer fits with the answer that for example Dembski would give. (Dembski’s filter wouldn’t infer design unless the pattern had specified complexity, but the Mandelbrot set is not complex. Dembski’s filter sometimes won’t infer design even when something is designed though, so from the fact that Dembski’s filter doesn’t infer design, we can’t infer that the pattern was not designed.)

I should note that, in practice, Mandelbrot sets are produced by designers — the people who wrote the computer program to produce them. What I’m interested in is if we (somehow) came across something like a Mandelbrot set in nature — say, in the pattern of a leaf. Would that pattern provide evidence for the existence of God?

To read more about these sorts of issues, see my new book, Seeking God in Science: An Atheist Defends Intelligent Design.