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Mc Intoshs Law

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Mc Intoshs Law

McIntosh's Law of Thermodynamics

by Derek Potter


Creationists often say that evolution is contrary to the second law of thermodynamics (2LT or SLOT) and hence impossible. Such a statement is liable to be met with uncomprehending stares from physicists who are not familiar with creationism. As its name suggests, thermodynamics is about the flow of heat. Why on earth should a law about heat flow have any bearing on whether evolution is possible?

It turns out that 2LT refers to a physical quantity called entropy which is sometimes loosely described as a measure of the microscopic disorder in a system. Entropy is also a indicator of the 'mixed-upness' of a system and indicates thermal energy that is no longer available for conversion into useful work. Entropy cannot decrease spontaneously in an isolated ("closed") system. Hence, say creationists, order cannot arise spontaneously in nature. The argument goes back at least as far as Henry Morris's The Remarkable Birth of Planet Earth, 1974, and is hinted at in The Genesis Flood (Whitcomb and Morris, 1961).

However it is obvious that this argument is wrong for at least three reasons. Firstly, living things are not isolated systems. Individual organisms are not isolated because they feed off sunlight or each other. Secondly, their genetic information, which is what we are interested in, is not a thermodynamic system at all. Thirdly, the meaning of the word "disorder" in 2LT is very precisely defined in terms of microstates. It has nothing to do with structure or function in living things. Any of these alone is sufficient to refute the Argument from 2LT.

Thus the argument is traditionally answered by a one-liner: "living things are not a closed system". End of subject. Nevertheless one cannot help but feel a twinge of sympathy for creationists who see their pet sophistry swept aside on a technicality about heat flow.

It doesn't seem to stop them though, as they continue to tell us that new information cannot arise in nature. By now, of course, we are light-years away from thermodynamics. It is true that Shannon information (e.g. data on a computer disk) has a mathematical parallel to thermal entropy. Yet the irony is that 2LT, if it applied at all, would actually mean that such information can only ever increase spontaneously! But in any case, Shannon information has nothing to do with the meaning or usefulness of the information as required to make it relevant to evolution. Again, creationists seem to miss these two rather important points, either of which instantly invalidates their argument.

So there the matter would probably have rested were it not for the fact that creationists have a specialist in thermodynamics, Professor Andrew McIntosh, in their ranks. Non-UK readers should note that in the UK, "professor" is not merely a courtesy extended to all teachers, it is a prestigious title bestowed in recognition of someone's authority in a subject. If anyone knows about 2LT it should be McIntosh. Yet the Argument from Authority must surely be undermined by a Press Release from his employers, the University of Leeds, saying "Professor Andrew McIntosh's directorship of Truth in Science, and his promotion of that organisation's views, are unconnected to his teaching or research at the University of Leeds in his role as a professor of thermodynamics. As an academic institution, the University wishes to distance itself publicly from theories of creationism and so-called intelligent design which cannot be verified by evidence."

Compartmentalization of one's ideas is one thing, but it is clear that McIntosh does not play that game when away from work. A comprehensive summary of his theories is to be found on the Answers in Genesis website under the heading Andrew McIntosh, mathematics at

This is an extract from one of his books, In Six Days. The document misapplies quite simple physics to "prove" irreducible complexity and intelligent design. Given McIntosh's acknowledged authority in thermodynamics, it behoves us to see exactly what he is saying. This will require reference to the basic physics behind thermodynamics, namely statistical mechanics. The subject itself is non-controversial and can be checked out in Wikipedia [see this link] or an undergraduate text. The problems arise in where exactly its theorems can be applied and where they cannot.

Andrew McIntosh, mathematics

McIntosh devotes the opening section to a discussion of World Views. This has no bearing on science, though one gets the impression he is trying to soften his readers up into a frame of mind that is more receptive to the subsequent material. In particular, it seems we need to be open to the idea of an invisible un-named thing that likes to tinker with biochemistry when no-one's looking, its wonders to perform.

Be that as it may, the next section is entitled Order and the Second Law of Thermodynamics, which sounds more promising. Here, McIntosh describes entropy in strictly thermal terms and is very clear that 2LT is inviolate. He then sweeps on to assure us that "entropy is effectively a measure of the disorder in that system"... "In overall terms, disorder increases, cars rust and machines wear out." He then applies this principle to the genome. Finally, for no obvious reason, he cites Prigogine, saying "Despite attempts by G. Nicolis [and I.] Prigogine and coworkers to find auto-organization by random processes within living creatures, sustained order can never be achieved, because no new information is available."

Now this is a truly amazing sequence. 2LT is a law. It cannot be broken. The principle that things fall apart is a homely truism about man-made objects. It is already well documented as Sod's Law. McIntosh subsumes both in a universal principle saying "There is a fundamental law in the universe to which there is no known exception... In overall terms, disorder increases... No spontaneous reversal of this process has ever been observed for a closed system." Which is true - as long as you mean microscopic disorder. However it is clear that McIntosh wants to apply it to macroscopic things since he uses machines breaking down as the example. So important is this "fundamental law" - hitherto unknown to science - that it deserves a name in honour of its discoverer: McIntosh's Law.

Unfortunately it is clearly untrue. All systems without exception are subject to 2LT. However, 2LT does not forbid macroscopic order from arising spontaneously. Just shake some mud with some water and leave it to stand. Lo and behold, the particles sort themselves out and you get beautiful layers forming at the bottom of the jar, coarse material at the bottom, fine stuff at the top. McIntosh's examples are selective. Cars certainly rust and machines do wear out - but crystals form and embryos grow as well.

Both 2LT and McIntosh's examples illustrate a fairly simple principle called the Equal Probability Assumption (EPA), which is made in statistical mechanics. Briefly it says that all microstates are equally likely. Obviously, if we see a system with a certain amount of "order" imposed on it, most microstates are ruled out: only the ones that meet our criterion for order are possible. However, since nature has no preferences, it follows that, given enough time for it to settle, the system invariably ends up in one of the much more abundant "disordered" states. This is the basis of 2LT. The notion of order only comes into it because, by definition, order is only a small subset of all possible conditions. This leads to the popular illustration "rooms get untidy, they don't tidy themselves". The reason is that there are many more ways for a room to be untidy than there are for it to be tidy and the room has no overwhelming preference for some states over others.

The EPA itself is sufficient as a basis for statistical mechanics. It can be precisely justified in the case of microstates because the fundamental laws governing the evolution of the system are time-reversible - which leads fairly naturally to the EPA through some rather mathematical reasoning. (Mathematicians would probably work with volumes of phase space rather than "numbers of microstates".)

However, the EPA is not justified in the case of states defined on macroscopic variables. Temperature and pressure, for example, just define a phase space of two dimensions. The phase space of the microstates, where EPA applies, may have of the order of Avagadro's number of dimensions! Not surprisingly, nature does prefer states where the temperature and pressure are evened out: there are many more such "disorderly" microstates than "orderly" ones where the gas molecules are rounded up into a corner of the box.

As a matter of fact, the same reasoning could be applied to any identifiable subset of the microstate ensemble. If we choose to label some states as "gruesome" then EPA entails that gruesomeness cannot spontaneously increase in an isolated system.

McIntosh's example of rusting is not fundamental physics either. In fact, the chemical reaction is a complicated re-arrangement of electronic orbitals and the process involves the release of energy as heat. The heat energy has countless possible modes, both as photons radiated away and as phonons vibrating the solid. Hence the process is unlikely to reverse itself significantly, though the odd molecule may very well break up in a spontaneous reversal from time to time.

McIntosh's Law therefore applies in many situations, but especially in cases where humans have a preference for particular states of the system and nature does not. McIntosh puts it the other way round, implying that nature actually abhors order. This is incorrect. McIntosh's Law arises precisely because, in most cases, nature has no preferences at all. There is no mysterious "fundamental law" about it.

But what of those instances when order does arise spontaneously? Crystallisation is a good example. There are even some substances, like ceric sulphate, that are less soluble in hot water than cold. Classical thermodynamics tells us the entropy increases as heat is added. Yet, in this case, the crystalline "order" increases at the same time. Clearly this is another exception to McIntosh's Law. 2LT and McIntosh's Law are not even remotely interchangeable.

In some cases, nature does have preferences (though never at the microscopic level). Nature has a preference for things to lie on the ground. Apples and walls fall down and, what is more, they stay down. This is because the laws of mechanics are not reversible: kinetic energy is dissipated as heat on impact. Otherwise the apples would bounce for ever. Yet on one view, apples lying all at the same height is more orderly than having them bouncing all over the place. The order arises because macroscopic collisions are dissipative - irreversible. Thus nature has a preference for some states: the ones that there is no escape from. Gravity without dissipation just leads to bouncing and no orderly layers of apples on the ground.

McIntosh's Law ought to apply to piles of apples but it is generally not held to do so because it only applies to certain types of order. One must assume that McIntosh means states that create the "appearance of design". Machines wear out, living things mutate and die out.

The last steps in the argument take us from McIntosh's Law to some arcane work that failed to produce auto-organization, then, finally, to his interpretation that this failure was "because no new information is available". The only hint as to what he means by that is the preceding statement: "That which is dead ... has no teleonomy within it to convert the sunís energy to useful work". It is beginning to look as though he is not talking about information at all but purpose. Yet he wants to apply Mcintosh's Law to purpose itself: presumably because it always works at the microscopic level of 2LT and often works in everyday situations where we prefer machines to be free from rust.

This impression is confirmed by the next section entitled Entropy, information and the living world. Here McIntosh argues against abiogenesis by chance, a pointless task really as no-one suggests that life arose that way - unless, of course, the universe is ridiculously big, in which case almost anything will happen by chance somewhere. But it is clear that McIntosh is suggesting that the organisation of the first replicators needed a lot of structure, function or purpose and that such things cannot have arisen spontaneously because it's contrary to his Law - and his Law is proved by the fact it works for 2LT.

Oddly enough, he grudgingly acknowledges that science doesn't invoke pure chance at all but suggests a kind of molecular evolution that preceded cellular life. He says "Though Dawkins has argued for a seemingly endless series of small advantageous mutations singled out by natural selection operating at the micro level there are formidable arguments against his position" and then proceeds to cite Behe's ideas of irreducible complexity to claim that chance is the only mechanism available to orthodox science. "The microbiologist Behe has also ably rebutted Dawkins... there is no mechanism in Darwinian evolution to add new information to a species at the macro level." Which, of course, is precisely where Behe is wrong since there clearly is - that is the whole point of Darwin's theory: that "macro" changes arise out of many "micro" changes. Behe, of course, compounds his own error by asserting that changes to the "information" do occur but they are always harmful. McIntosh does not distingish between abiogenesis and evolution when discussing the DNA code. This, then, is the build-up to irreducible complexity.

Since all scientists except creationists agree with Dawkins and most laugh at Behe, why does McIntosh attack this strawman?

Thus McIntosh as good as says '2LT is really an unbreakable law about entropy but it's also a manifestation of the rule of thumb that everything degrades. So the rule of thumb is an unbreakable law and the genome must degrade.

In the next section entitled Flight in the natural world Ė complexity all can observe, McIntosh demonstrates that he cannot imagine how flight could evolve, from which he deduces that it did not. For example "One can envisage the odd scenario of the supposedly half-evolved hummingbird either with the ability to hover and a sparrow beak, unable to feed, or the long beak but no ability to hover, which would mean flying into the flower with no ability to stop!" It just isn't worth analysing such a simplistic Argument from Incredulity. The rest of the article is predominantly more of the same. A flat refusal to admit that "information" - in the loose sense of function - is added to the genome all the time by mutation and natural selection.

McIntosh's thinking is quite clearly revealed towards the end. "Those [examples] which have been considered in this chapter could be added to by many more intricately balanced mechanisms which overwhelmingly testify to a creative hand."

Only they don't. They only ever occur in systems which differ radically from man-made machines. The systems replicate. No lathe ever made another lathe except by the agency of a human operator. Living things do it on their own. If McIntosh could demonstrate that living things popped up fully formed then he could argue that their design speaks of intelligence. But since they replicate spontaneously, with variation and natural selection, his analogy is completely false.

After that, the fact that his argument cannot be traced back to thermodynamics but only to a law of his own devising may come as no surprise.

© Derek Potter 2007

Notes: There is a discussion on Derek Potter's article above in the BCSE's public forum. It is in Science sub-forum. Please feel free to join the forum and comment, make suggestions, debate and so on.

Science just Science has a pretty good article on its wiki about the abuse by creationists of the 2nd Law of Thermodynamics. This is a pretty good primer for thse trying to get their heads around it and can be found at

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