OK everyone, I promise that this is the last ID post from me for a while. (If Gene posts on the topic though, I will almost certainly comment on the thread.)
Anyway, what I will quickly do here is summarize the No Free Lunch (NFL) theorems, and then William Dembski's attempt to apply them in the arena of the origin of life. Despite the official shrugging off by experts, I think Dembski has hit upon an incredibly powerful argument, and if he did nothing else worthwhile in his career (some might say this is true!) he would still be a genius.
OK so first let's go over the NFL theorems: Basically they show that no optimization algorithm can outperform another, over the entire domain of all possible problems. Now this is a shocking result, and if it doesn't shock you, you probably don't grasp what it is saying. So let me put the result in a concrete way, using an example that others (I think maybe the original authors?) have used.
Suppose the problem is to find the highest elevation on a landscape, where the surface is divided into a finite number of sectors. You have to choose a search algorithm to find that highest spot, where you start at some random location and can only see the elevation of adjacent sectors.
So the NFL says that, over all possible landscapes (and of course this is spelled out formally in the proof), there is no reason that any one search algorithm would do better than another. In particular, the algorithm that says, "Look around you, and go up the steepest incline" does no better on average than an algorithm that says, "Pick a direction at random and then head that way." Even more incredible, the first algorithm doesn't even outperform the algorithm that says, "Look around and go towards the lowest elevation available."
(I confess that this last part seems crazy to me; you would think it would be easy to show that the first algorithm weakly dominates the third, but apparently over the entire class of landscapes it doesn't. I asked an expert if he could intuitively explain this, perhaps by describing just one landscape where the third one does better, but he either never replied or admitted he couldn't put it into simple terms.)
OK so are we all set on what the NFL theorems say? The reason for their name is that of course, if you know something beforehand about the type of problem you want to solve--equivalent to knowing which subset of possible landscapes your algorithm will encounter--then it is easy to find algorithms that will outperform others. But there is "no free lunch"; you can't search a little bit to determine the type of landscape, and then pick the appropriate algorithm. (Because that would itself just be an original algorithm facing the entire domain of possible landscapes...) So you have to assume a priori knowledge of the answer before setting up the search, and hoping to have better than random chance of finding the answer.
I hope you now see where this is going. In the evolution debate, an ignorant creationist might say, "Random chance can't explain the complexity of life! Just watch a fetus developing in the womb! You call that a crap shoot??" But of course, the sophisticated answer is that Darwinian evolution doesn't rely merely on chance, it relies on random mutations which are then acted upon by natural selection.
So what Dembski tried to argue is that this is begging the question; it is trying to get a free lunch out of nature. The biologists would concede that mere trial-and-error could not, even with billions of years to operate, have possibly given rise to life as we know it. But Dembski then invokes the NFL theorems. Over the domain of all possible environments, why should we expect the algorithm of natural selection to "find" these complex arrangements of matter? Again, in general there is no reason to suppose that natural selection would do any better than random chance, unless the landscape for this "problem" (i.e. the conditions on earth over the last few billion years) happened to be in the subset of possible landscapes where natural selection outperforms random chance. And so, Dembski concludes, if you admit that it would be crazy to suppose chance alone gave rise to life, then the NFL theorems force you to admit that random chance + natural selection is also just as "lucky" for yielding life.
Now then, what has been the official response to this argument? Read Wolpert (one of the NFL authors) here, and biologist Allen Orr here (page 4). The official response is that the NFL theorems don't apply to biological evolution, because there is no fixed landscape. Rather, there are multiple creatures "optimizing" on a landscape that includes each other, so the landscape itself changes. In Orr's words:
Another problem with Dembski’s arguments concerns the N.F.L. theorems. Recent work shows that these theorems don’t hold in the case of co-evolution, when two or more species evolve in response to one another. And most evolution is surely co-evolution. Organisms do not spend most of their time adapting to rocks; they are perpetually challenged by, and adapting to, a rapidly changing suite of viruses, parasites, predators, and prey. A theorem that doesn’t apply to these situations is a theorem whose relevance to biology is unclear.
Now I think this is a crushing admission of defeat by Orr. Here's why:
(1) Is he conceding that random mutation + natural selection can't explain how a single line of organisms could adapt to a lifeless world?? That's problematic because for one thing, intuitively it is a lot easier to see how the Darwinian story would work in a fixed environment. If you admit that the theory shows it doesn't work there, then I think it's little comfort to say, "But technically the assumptions of NFL don't hold for co-evolution, so it's an open question whether mutation+natural selection work when there are other organisms at work." It's problematic for a second reason because co-evolution can only kick in after the origin of the first form of life!!
(2) I realize there must be some subtlety in the proof, but I don't see why you couldn't easily incorporate the other organisms as part of the original "fixed" landscape. The NFL theorems have a very abstract, broad specification of the class of problems. E.g. it would have been silly had Orr said, "NFL only applies to a fixed landscape, but in the real world there are volcanoes that sometimes erupt." I.e. a volcano that erupted 18,456 time units after the start of the simulation could easily be incorporated as just another dimension in the original fitness landscape; the problems in general aren't really just 3D surfaces where the object is to find the highest point. That was just an easy picture to illustrate the results. So, take any one organism's point of view, and consider all the other organisms as just part of the landscape to which it is adapting. I don't see how this changes the problem. (BTW the game theoretic co-evolution paper that Wolpert put out later really didn't look anything like evolutionary models; there are players engaging in a tournament and finding a "champion" etc. I'm pretty sure even Wolpert himself acknowledges that those later models don't have much to do with the evolution argument.)
Incidentally, I had a short email exchange with Orr back in the day. I asked him point (1) above, something like, "Doesn't it seem odd that you are apparently admitting that evolution couldn't explain creatures adapting to a fixed, inorganic world, while you are saying it is capable of explaining adaptation to an even more complicated world?" He didn't answer that email. (I'm not saying this as a shocking example of his cowardice, I'm just reporting that he never answered that question.)
OK I promise no more new blog posts on ID from me for a while... We can argue in the comments if you'd like.
UPDATE: I found Orr's stand-alone review of Dembski's No Free Lunch. This has a much stronger response to the NFL argument than the one I quoted above, though I think it is still fairly weak. Orr raises a bunch of other good objections to Dembski, though.
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