On Irreducible Complexity
Update: It appears Catholic Answers has made the highlight clip video private. I suspect they released it sooner than they wanted. Hopefully it will be public again shortly. Sorry about that!
Catholic Answers just uploaded a “highlight clip” from my recent appearance on Catholic Answers Live where I respond to the question of whether complexity in life “proves” God.
While I haven’t seen anyone misunderstand/misrepresent what I said in this clip, I thought further context would be helpful (if only to hedge against the inevitable ; ).
If you watch the clip, you’ll see I began by distinguishing two types of “design” arguments.
The first are arguments from teleology or natural regularity. Such arguments include Aquinas’s 5th Way and have little to nothing to do with complexity. Rather, they are interested in identifying ineliminable directedness (final causality) in nature and then arguing nothing could exhibit final causality unless there is an “undirected director” which can only be metaphysically unpacked as the absolutely simple God of classical theism. I did not detail 5th Way argumentation in the aforementioned clip, but for those interested in understanding how it works, see chapter 3 in Feser’s Aquinas.
The second argument from design concerns complexity. Such arguments trace famously back to William Paley, though I focused on recent developments like those from Michael Behe. What I intended to highlight was the notion of irreducible complexity.
Before getting into it, let me mention two other differences between these arguments. First, arguments from teleology are claimed to be metaphysical demonstrations, contending the phenomena under consideration could not possibly be accounted for apart from that which can relate concepts – namely, a transcendent mind that is itself utterly simple (whose act and object of understanding are identical). They are neither probabilistic arguments nor utilizing inference to the best explanation. By contrast arguments from complexity are probabilistic and utilize inference to the best explanation; they aim to show that it is virtually impossible (= so vastly improbable) that naturalism could account for the phenomena in consideration – in our case, irreducible complexity – even if it is not logically or metaphysically impossible. Thus, we should prefer the theistic hypothesis over the naturalistic one. The danger of the second approach is it could open someone to the god of the gaps charge, though I often find that charge particularly weak and something that can easily cut the other way via “naturalism of the gaps”. Nevertheless, it’s a possible that science could discover something different about the way the world operates. Unlikely in this instance, but possible… I suppose.
OK, enough of that. Let us now try to appreciate the argument from irreducible complexity, which is often misunderstood. And, please understand: I present this consideration as someone who was previously skeptical but is now friendly to this line of argument (see my interviews with Behe here, here, and here).
The first thing to note is the complexity Behe is interested in is not just one of elegance. Rather, it is one of functional interdependence between parts. Which is to say, in the absence of any such part, the system collapses. Behe uses the example of the bacteria flagellum which is (essentially) a rotary propeller within the membrane of a cell. Like many biological systems, remove just one of its components and the entire thing falls apart; it no longer performs its function. The problem we see emerging for naturalistic-evolution in the face of irreducibly complex systems is this: we cannot say irreducibly complex systems evolved piece by piece, since the system only works if all the parts are present, correctly shaped and situated, and functionally correlated and cooperative with one another toward some specific effect or range of effects. It is just incredible (as in, not at all credible) to think irreducibly complex assemblages could have come about as accidental byproducts of other evolved items or as the result of older parts spontaneously assuming newer functions. In other words, irreducibly complex systems do not admit of degrees. This is a problem for Darwin’s mechanism and naturalism more broadly, which must explain biological systems via gradually emerging states.
Some might say irreducible complexity decidedly refutes naturalism and atheistic evolutionism. (Of course, irreducible complexity is by no means incompatible with evolution within a theistic context, because God guides; so, again, I emphasize that this is not an argument against evolution per se, and especially not against THAT evolution occurred; it only concerns HOW evolution occurred). However, what I want to say is more modest and begins by asking what worldview hypothesis better leads us to expect irreducibly complex systems, which are marvelously abundant? I think the answer is obvious; theism better predicts such systems. Irreducibly complex systems are highly surprising according to a naturalistic framework. In which case, our encounter of irreducibly complex systems, if not decisive against naturalism, counts as evidence – strong evidence, I suggest – against naturalism. That is how I like to frame the argument.