Can a materialist believe in the theory of evolution? I doubt it.
Back when I was in junior high and high school, I remember being given flow chart-style expositions of what textbooks call “the scientific method”. It went something like this: 1) ask a question; 2) formulate a hypothesis; 3) do an experiment; 4) if your hypothesis is verified, it gets promoted to a “theory”; 5) keep doing tests; 6) eventually, the “theory” gets bumped up to being a “law”. There are certainly criticisms that could be made of this. Flow charts always do some violence to what is fundamentally a creative process. The “hypothesis” stage is often unnecessary for science fair-type projects–often a student would (and logically should) remain agnostic about the outcome of his experiment until the data is in, but his teacher forces him to “hypothesize” some answer in deference to “the scientific method”. A decade as a research scientist and I still don’t know what the difference between a “theory” and a “law” is supposed to be. But, given that the point is to introduce junior high kids to scientific ways of thinking, the standard exposition isn’t bad.
One thing that’s good about it is that it gets across the idea that scientific explanations have varying degrees of certainty. “Science” doesn’t always speak with the same assurance. If you don’t believe in blackbody radiation, you’re crazy. If you don’t believe in dark matter, the evidence right now weighs against you, but your opinion is respectable, and I wouldn’t be shocked if it turned out to be right. If you think string theory is bunk, you are (I suspect) in agreement with a silent majority of physicists.
So I started thinking–how far does scientific certainty go? There’s a school of thought that says that natural sciences never achieve real certainty: every theory is just one experiment away from disproof. So, for example, the 1/r^2 laws for electricity (Colomb) and gravity (Newton) have been very well tested. Still, that gives no certainty that a slightly more accurate measurement wouldn’t find deviations. And, in fact, we do predict and observe slight deviations due to QED and general relativity, respectively. I expect that someday deviations from these theories will also be found, when we can test extreme enough conditions at high enough accuracy.
But not all scientific theories present themelves as exact and fundamental in this way. Consider the following three theories: 1) the connection between statistical mechanics and thermodynamics; 2) evolution by random genetic variation and natural selection; 3) the existence of souls of animals. The first is due to Boltzmann, Maxwell, and Planck; the second to Darwin; the third to Aristotle. I think it is flatly impossible–inconcievable–that any of these three theories could be disproved by any future observation. As soon as you understand these theories, you realize that they must be true; the only logically contingent question is whether the circumstances for their application are ever actually realized (and these questions have obviously affirmative answers).
Not only does the process of natural selection not tax our credulity; we realize that, assuming there are heritable traits and that some traits give one a leg up in the reproductive race (and who could doubt either claim?), natural selection will happen, given only enough generations. It would take divine intervention to stop it from happening. It doesn’t matter if we don’t know exactly how mutations happen or how a given adaptive trait functions. The theory is independent of these details.
Similarly, it could be that we have much to learn about the particles that make up atoms, but none of that can affect the laws of statistical mechanics. The identification of entropy with a multiplicity of microstates and of temperature with entropy’s energy derivative (and, for a gas, with the average kinetic energy) are permanant gains in knowledge. They have to do, not with unexplained mathematical rules, but with identifying what things (entropy, temperature) fundamentally are. When one understands what entropy is, one sees that of course it will never decrease for a closed system. The most basically questionable part of thermodynamics is the first law, because it depends on energy conservation, a presumed fundamental law of nature of whose veracity we can never really be certain. (It’s one of those permanantly-one-experiment-from-disproof laws.)
Then there’s Aristotle’s claim that living beings have substantial forms. Moderns scoff at this “unscientific” idea, but of course it’s used in every page of every medical textbook in existence. We assume that things like substantial unity (that we can identify what is and isn’t part of the organism), function (ask your doctor what the function of the liver is, and see if he chides you for asking an unscientific question), and identity through material change will apply to living things, and we are not disappointed. Zoologists and paleantologists make predictions based on the assumption that animals are self-moving, and that they will act for their own preservation and propagation, and these predictions are confirmed. Substantial unity–the “soul”–is certainly scientific. It may not be just scientific–it is also ontological–but it’s not less than scientific, because the scientists could never do without it.
Evolution, thermodynamics, and the soul are certain knowledge because they are formal knowledge. They have to do with patterns that we recognize, and as such they have a real intelligibility that material knowledge–e.g. knowledge of the fundamental laws of the matter that makes us up–lacks. To one who apprehends that he has a soul–that he is a unity of drive, intelligence, and action–it wouldn’t make sense to be told that scientists have done some very careful tests of the cells in his body or of his psychological states, and they have learned that he actually has no principle of unity, that “he” is nothing but an arbitrarily identified aggregate of matter. Whatever these scientists have been doing, they could only have been learning more about the matter that incarnates the vital pattern he calls himself. The existence of the pattern is not open to doubt once one has apprehended it.
We all realize that this idea of the soul is philosophically tinged. We expect to have to defend it from the empiricists and materialists. “What part of the body is the ‘soul’ in?” they jibe, and we Aristotelians roll are eyes and answer back something like “What part of the statue is the ‘shape’ in? What pigment in the painting is the ‘pattern’made of?” The funny thing is that all other definitive scientific theories are in the same boat. If he really refuses to believe anything he can’t touch or see, the materialist should not believe in natural selection. If we “zoom in” to the life story of any individual organism, natural selection disappears. It’s not some kind of magical force that smites the unfit. Any given animal that died before reproducing was killed by something else–hunger, disease, predators, etc. No particular animal died because of natural selection, just as no particular cell in your body houses your soul. Substantial forms and evolution are in the same boat. Similarly, if one “zooms in” to a single atom or molecule, the concepts of entropy, temperature, and pressure become meaningless.
It would seem that mid-twentieth century physics’ reductionist turn was at least partly mistaken. Vocal reductionists like Stephen Weinberg made high-energy physics–fundamental laws about elementary particles–the measure of all knowledge. If I’m right, one can only have real and certain knowledge to the extent that one’s theory conceptually divorces itself from these fundamental laws. Statistical mechanics works by throwing away everything but energy and multiplicity. Evolution works by throwing away everything but heritability and adaptivity. Aristotelian biology (i.e. anatomy and physiology) works by cataloging form and discarding matter. (Thinking themselves materialists, biologists like to say that they “turn over” the basic properties of the matter in living beings to the chemists and physicists, but the fact that they can “turn over” this subject and continue on their way without trouble shows that it is actually formal causality that they’re dealing with.)
Filed under: philosophy of science |