Over at his blog

*Uncommon Descent*, William Dembski is

linking to an online lecture by mathematician Granville Sewell arguing that evolution runs afoul of the second law of thermodynamics. The lecture is thirteen minutes long, but it does not contain anything that Sewell has not

said before.

It is significant that Dembski is linking so enthusiastically to this argument. You see, the thermodynamics argument is one of the very worst creationists have ever used. It is wrong, of course. But more than that it is wrong in a way that betrays an extreme simple-mindedness about science in general and physics in particular.

As a result, the thermodynamics argument has become a symbol for the sort of mind-numbing ignorance that is the stock-in-trade of creationists. How could anyone take creationists seriously when they parroted such obvious nonsense about thermodynamics?

And it was precisely this level of silliness that ID proponents were keen to avoid. Until recently. Now we have William Dembski, who provides most of the tiny amount of intellectual oomph the ID folks can claim, supporting this ridiculous argument.

The basic argument is this: The second law states that a spontaneous, natural process can only lead to an increase in the entropy of a system. Entropy is roughly a measure of disorder or complexity. So the second law implies that natural processes can only cause things to become more disordered and less complex over time. But evolution asserts that natural processes have caused organisms to grow more complex over time. This is a contradiction, and since no one is inclined to abandon the second law, evolution must not be correct.

But this is a cartoon version of the second law. After all, you don't need fancy principles of thermodynamics to argue that the growth in complexity of organisms over time is something that requires a special sort of explanation. It is a simple fact of everyday life that without maintenance things tend to break down and fall apart.

Everyone agrees that the growth in complexity that evolutionists claim took place over the course of natural history requires an explanation. And biologists have one. Many generations of natural selection acting on random genetic variations can cause the average complexity of organisms to increase.

This is not theoretical. Natural selection has demonstrated its ability, in both the field and the lab, to increase the level of order and complexity in organisms. The same principle is at work in artificial life experiments, and in the use of evolutionary algorithms in engineering problems. Granted, the experiments I am referring to tend to show relatively small increases in order, but that is enough to establish that no principle of thermodynamics prohibits known evolutionary mechanisms from increasing biological complexity.

Sewell himself inadvertantly concedes this. When it comes time for him to explain why natural selection is not an adequate explanation for the growth of biological complexity, thermodynamics goes out the window. Instead he simply parrots the irreducible complexity argument of which ID folks are so fond. That argument is incorrect, but of more relevance to this discussion is the fact that it has nothing to do with thermodynamics.

Let me make things even simpler. Things that are thermodynamically impossible do not occur. But natural selection is certainly capable in principle of explaining increases in biological complexity. Therefore, there is no principle of thermodynamics that says that evolution is an incorrect theory.

But let's push this a bit further. In certain physical situations it can be useful to think of the second law as a statement about order and disorder. Really, though, the second law is a mathematical statement. It says that the change in entropy of a system in going between two states must be larger than a certain mathematical quantity (the integral of

*dQ* over

*T*, for those who know some calculus and some thermo notation). The technical details of what this means need not detain us here.

If you make the added assumption that your system is completely isolated from the outside world, so that neither matter nor energy is crossing the boundary of the system, then the integral I mentioned ends up having the value zero, and the second law tells us that the change in entropy must be positive. In other words, the entropy must increase in this situation.

Creationists of old tended to ignore this assumption, and argued simply that the second law rules out any possibility of natural forces causing order to increase. Consequently, scientists generally replied that the Earth is not an isolated system, since we receive copious amounts of energy from the Sun. That's certainly an important observation, and it does, indeed, refute some primitive versions of the second law argument.

But the second law still applies when energy is crossing the boundary of the system, and in this case it says that the change in entropy must be larger than the mathematical function I mentioned previously. Entropy can, indeed, decrease in this situation, but the second law still makes a definite statement about the magnitude of that decrease. Sewell understands this, and gives a tolerable, if highly nontechnical, description of this fact.

Which makes his unwillingness to follow through all the more annoying. You see, any claim that evolution violates the second law must be backed up with a calculation. Sewell believes that the second law is a problem for evolution? Fine. Let him evaluate the integral I mentioned and show that the change in entropy has been smaller than it should be. Anything short of that is no longer an argument based on thermodynamics. It is just ye olde argument from personal incredulity, in which Sewell is expressing nothing more than his own disbelief that biological complexity could have evolved naturally.

The reason Sewell will not carry out this calculation is that he can not. No one can. Entropy calculations are always carried out in the context of a reversible process, and no one has the faintest idea how to describe a reversible process for assembling an organism from it's component atoms. That is why serious scientists do not try to apply the second law to biological processes in the simple-minded ways ID folks prefer.

But Sewell has another trick up his sleeve. He is fond of recasting the second law as a statement about probability. In his

*American Spectator* article he writes:

Natural forces, such as corrosion, erosion, fire and explosions, do not create order, they destroy it. The second law is all about probability, it uses probability at the microscopic level to predict macroscopic change: the reason carbon distributes itself more and more uniformly in an insulated solid is, that is what the laws of probability predict when diffusion alone is operative.

What Sewell is really doing here is taking a statistical mechanics view of things. The basic idea is this: Given a box that is filled with gas and has been sitting, untouched, for some time, we expect the gas molecules to be distributed roughly evenly throughout the box. We would be very surprised to find all of the gas on one side of the box with empty space on the other. We can explain this in terms of probability: There are vastly more configurations in which the molecules are distributed roughly evenly than there are where all the molecules are on one side of the box. So other things being equal, we can say that it is vastly more likely that we will encounter one of the even distributions. And the distributions in which the gas is evenly distributed can plausibly be said to be less ordered, and therefore have higher entropy, then the highly uneven distributions. This permits a probabilistic interpretation of the second law.

Sewell sums up his thinking here with the following formulation:

In these simple examples, I assumed nothing but heat conduction or diffusion was going on, but for more general situations, I offered the tautology that “*if an increase in order is extremely improbable when a system is closed, it is still extremely improbable when the system is open, unless something is entering which makes it not extremely improbable.*” (Emphasis in original)

Yes, of course. But so what? In his podcast Sewell describes evolution as being a “film running backwards” by which he means that we see complexity increasing in apparent violation of the second law (just like in a movie run backwards you might see the shattered pieces of a broken coffee cup reassemble themselves into a functional mug).

If he wants us to take this claim seriously, he needs to follow the dictates of his own theorizing. Does evolution require us to believe that something incredibly improbable has occurred in the course of natural history? Let Sewell carry out the probability calculation that shows that to be the case. Then let him explain what significance his calculation is supposed to have. (Improbable things happen all the time, after all). Once he has done that, he will have an actual argument, and we can revisit this subject at that time. Without such a calculation, he has only a lot of polysyllabic bluster.

The solar energy that enters the Earth every day fuels the chemical reactions that allow living organisms to survive and reproduce. This cycle of survival and reproduction ultimately leads to natural selection, which can, in turn, lead to increases in biological complexity. Minus that energy living organisms would quickly go extinct and evolution would not occur. So, to use Sewell's idiosyncratic phrasing, something is indeed crossing the boundary that makes an increase in biological complexity more likely.

If Sewell wants to retreat to the question of the origin of life, then he will have to confront the simple fact that the various sources of energy bathing the early Earth would have fueled the numerous chemical reactions that are believed to have led to the first primitive life forms. Once again, it is for him to back up his claims about probability with something more substantive than his own beliefs.

Sewell will have no more luck carrying out these probability calculations than he had with the prior, entropy calculation. And that is because these sorts of probabilities are effectively impossible to calculate. The probability of any particular set of outcomes of several billion years of evolution depends on far more variables than can possibly be included in a practical calculation. Probability theory finds many applications in biology, but this is not one of them. There is a reason real scientists do not talk about probabilty calculations in Sewell's haphazard manner.

The pattern in Sewell's arguments is now rapidly becoming clear. When he wants to impress us with the rigor of his argument, he talks about entropy and order and probability and the history of thermodynamics. But when it comes time to apply any of this to evolution he retreats to simple-minded arguments about films running backwards and atoms arranging themselves into microchips. The reason he does this is that, in reality, thermodynamics and probability play no role at all in his argument. As already discussed, he contributes nothing to the discussion beyond his own incredulity.

Sewell closes both his essay and his podcast as follows:

The development of life may have only violated one law of science, but that was the one Sir Arthur Eddington called the “supreme” law of Nature, and it has violated that in a most spectacular way. At least that is my opinion, but perhaps I am wrong. Perhaps it only seems extremely improbable, but really isn't, that, under the right conditions, the influx of stellar energy into a planet could cause atoms to rearrange themselves into nuclear power plants and spaceships and computers. But one would think that at least this would be considered an open question, and those who argue that it really **is** extremely improbable, and thus contrary to the basic principle underlying the second law, would be given a measure of respect, and taken seriously by their colleagues, but we aren't. (Emphasis in original).

But knowledgable people will not show any respect for Sewell's argument, because he has produced virtually no argument at all. He describes it as his opinion that evolution violates the second law. But this is not the sort of thing about which scientists are supposed to have opinions. We have ample evidence that evolution happened and that natural selection was the driving force of it. Biologists find evolutionary thinking to be very helpful in their research. If Sewell believes that it runs afoul of the second law nevertheless, then he needs to carry out the calculations that show that to be case. Otherwise he has only an opinion based on nothing.

These sorts of considerations should be obvious to anyone with a modicum of mathematical or scientific training. That they are not obvious to Sewell is another reason his quest for respect will be in vain.