A correspondent asked about “specified complexity” and the intelligent design of the eye. I explained why I much prefer the phrase “purposeful arrangement of parts” as a criterion for design — versus irreducible complexity, specified complexity, specified small probability, information, complex specified information, or other phrases.

The critical difference between ID and Darwinian evolution (and all other proposals for unintelligent evolutionary processes) is the involvement of a mind in ID. The philosopher Lydia McGrew once wrote that the basic question of ID boils down to the question of “other minds.” One of Alvin Plantinga’s claims to fame is that he argued fifty years ago in God and Other Minds that (I paraphrase) the perception of the existence of God is the same sort of problem as the perception of the existence of other minds.

Minds and Purpose

So how do we perceive the work of a mind? As I’ve written in my books (most extensively in Darwin Devolves), minds (and only minds) can have purposes. Thus, to the extent it can manipulate things, a mind can arrange parts to achieve its purposes. Of course, we ourselves have minds. And it is a fundamental power of mind that it can discern purposes. Thus we can recognize that a mind has acted by perceiving a purposeful arrangement of parts. There is no other way that I can think of by which we can recognize another mind.

For purposes of detecting other minds, “parts” can be virtually anything. Examples include: the purposeful arrangement of sounds in speech; words and letters in writing; mechanical parts in machinery; the timing of events in a surprise party; combinations of all those things; and an infinite number of other ways. There are many other things to say to fill this out that I can’t go into here (especially the issue of “spandrels,” that is, features that are unintended for themselves but are the side effects of constructing designed systems). Nonetheless, the overriding point is that we can only recognize design/mind in the purposeful arrangement of parts.

Zeroes and Ones

Other phrases that people use to indicate intelligent design all boil down to purposeful arrangements of parts. For example, Stephen Meyer likes to point out that we know intelligent agents produce information, so when we come across coded information in a computer program we can conclude it was produced by an intelligent agent. True enough. Yet how do we know there is information in a string of zeroes and ones — in a computer program? Only if we find that they are arranged for a purpose; that is, if the computer program has a function, if it can do something purposeful. In the same way, irreducibly complex systems resist Darwinian explanation, but how do we know they are designed? Because we see they can do something, that they have a purpose, they are a purposeful arrangement of parts. (As an aside, IC systems have two relevant properties — their discontinuous nature resists Darwinism and their manifest purposiveness strongly points to design.)

Finally, in the case of the eye, rather than “specified complexity,” I think it is much, much easier to parse design for a lay audience (or a professional one) as a purposeful arrangement of parts. Audiences will immediately recognize the purpose in the arrangement of the eye’s components. In my view, the phrase specified complexity only obscures the same meaning as found in purposeful arrangement. The “specified” in the phrase specified complexity is pretty much the same as “purposeful,” and “complexity” the same as “arrangement.” Yet the phrase “purposeful arrangement” is at once less mathy, less forbidding, more accessible, and clearer.