From eo12 Mon Jun 09 21:28:46 1997 Path: newsstand.cit.cornell.edu!news.acsu.buffalo.edu!dsinc!spool.mu.edu!uwm.edu!newsfeeds.sol.net!europa.clark.net!newsxfer3.itd.umich.edu!su-news-hub1.bbnplanet.com!su-news-feed4.bbnplanet.com!news.bbnplanet.com!enews.sgi.com!news.sgi.com!news1.best.com!kerberos.ediacara.org!there.is.no.cabal From: wilkins@wehi.edu.au.UNSPAM (John Wilkins) Newsgroups: talk.origins Subject: [Draft FAQ] Evolution and Philosophy Part 1 Date: 4 Jun 1997 20:14:21 -0400 Organization: Walter and Eliza Hall Institute of Medical Research Lines: 583 Approved: robomod@ediacara.org Message-ID: NNTP-Posting-Host: kerberos.ediacara.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: Yet Another NewsWatcher 2.4.0 I hope this posts OK, or I've just wasted a lot of bandwidth. Brett Vickers (keeper of the FAQs) asked for an FAQ on the philosophy of science and evolution. This, I hope, is it, although I have covered a number of other philosophical issues that are related. I'm posting in several parts. Apologies for the volume. A Web version (with better graphics) is at Evolution and Philosophy: An Introduction ===================== Version 1.0 beta 3, incorporating the earlier Evolution and Metaphysics essay from the talk.origins FAQ site Copyright © 1996, 1997 by John Wilkins John Wilkins Acknowledgements Thanks to Peter Lamb, Tom Scharle, Loren Haarsma and Larry Moran for criticism, comments and suggestions on an earlier FAQ. This version has benefitted greatly from comments and references from Peter Lamb, Chris Nedin, Richard Harter, and James Franklin. ================= Contents Introduction ------------ * The 'tautology' of fitness * The nature of science * Predictions and explanations * The 'species problem' * Reductionism and biology * Progress and Teleology * Naturalism * Social Darwinism * Worldviews and science ------------ Bibliography Feedback welcomed! =================== Summary: evolution is a philosophical focus, but the relation is not simple. This essay summarises and deals with the main modern issues of evolution and philosophy. Evolution and philosophy have a relationship as old as the idea of evolution itself. This is a partly due to the fact that science and philosophy only separated about the time evolutionary theories were being first proposed, but also because - especially in the Darwinian context - evolution was opposed to many cherished philosophical doctrines. The first main criticisms of evolution lay in the idea that species were eternal types, and so by definition species could not change. More recently, criticisms have rested on the notion of science itself, that evolution fails to meet the standards of true science, views that also were expressed at the time of Darwin and earlier. If we are to understand these criticisms, we must understand the philosophy of science in some detail. Many other topics of philosophical debate have been raised, and they are briefly reviewed: reductionism, progress and directionalism, teleology, naturalism, and evolutionary ethics. Not all of them are related to creationism, but all apply to antievolutionary arguments by those working from a humanities slant. Finally, the view has been put even by philosophers like Popper who admire and accept evolutionary theory that it is a tautology and metaphysical rather than science. My conclusion is that evolution, especially the modern theories, is science at its best, and when it and the nature of science is considered realistically, evolution is not lacking from a philosophical perspective. This essay will deal with these philosophical questions and misunderstandings about evolution: 1. Is the principle of natural selection a tautology? [The 'tautology' of fitness] 2. Is evolutionary science real science? [The nature of science] 3. Can evolutionary theory make predictions? [Predictions and explanations] 4. Are species fixed types? [The 'species problem'] 5. Should biology be reduced to physics? [Reductionism and biology] 6. Is evolution progressive or directional? [The ladder of progress versus the bush of evolution] Is there a goal to evolution? [Teleology in biology] 7. Does science have to be 'naturalistic'? [Ruling out supernatural explanations] 8. Does the theory of evolution impose a 'might is right' morality? [Social Darwinism] 9. Is evolution a metaphysical system akin to a religion? [Worldviews and science] I apologise for the wordy and heavily referenced nature of this essay, but the field is complex and deep, and those who would understand the issues had better be prepared for some reading. Nevertheless, I have tried to broadly summarise the main issues. The references will give those just entering the subject a starting point. =================== A good tautology is hard to find Summary: the claim that evolutionary theory is a tautology rests on a misunderstanding of the theory. Fitness is more than just survival. The simple version of the so-called 'tautology argument' is this: Natural selection is the survival of the fittest. The fittest are those that survive. Therefore, evolution by natural selection is a tautology (a circular definition). The real significance of this argument is not the argument itself, but that it was taken seriously by any professional philosophers at all. 'Fitness' to Darwin meant not those that survive, but those that could be expected to survive because of their adaptations and functional efficiency, when compared to others in the population. This is not a tautology, or, if it is, then so is the Newtonian equation f =ma [Sober 1984, chapter 2], which is the basis for a lot of ordinary physical explanation. The phrase 'survival of the fittest' was not even Darwin's. It was urged on him by Wallace, the codiscoverer of natural selection, who hated the phrase because he thought it implied that something was doing the selecting. The phrase came about because Darwin had made an analogy with 'artificial selection' done by breeders, something Wallace hadn't done when he developed his version. The phrase was originally due to Herbert Spencer some years before the Origin . However, there is another, more sophisticated versions, due mainly to Karl Popper [1976: sect. 37]. According to Popper, any case where species exist is compatible with Darwinian explanation, because if those species were not adapted, they would not exist. That is, Popper says, we define adaptation as that which is sufficient for existence in a given environment. Therefore, since nothing is ruled out, the theory has no explanatory power. This is not true, as a number of critics of Popper have observed since (eg, Stamos [1996]). Darwinian theory rules out quite a lot. It rules out the existence of inefficient organisms when more efficient organisms are about. It rules out change that is theoretically impossible (according to the laws of genetics, ontogeny, and molecular biology) to achieve in gradual and adaptive steps (see Dawkins [1996]). It rules out new species being established without ancestral species. All of these hypotheses are more or less testable, and conform to the standards of science. The answer to this version of the argument is the same as to the simplistic version - adaptation is not just defined in terms of what survives. There needs to be a causal story available to make sense of adaptation (which is why mimicry in butterflies was such a focal debate in the teens and twenties). Adaptation is a functional notion, not a logical or semantic a priori definition, despite what Popper thought. The current understanding of fitness is dispositional . That is to say, fitness is a disposition of a trait to reproduce better than competitors. It is not deterministic. If two twins are identical genetically, and therefore are equally fit, there is no guarantee that they will both survive to have equall numbers of offspring. Fitness is a statistical property. What 'owns' the fitness isn't the organism, but the genes. They will tend to be more often transmitted so far as what they deliver is better 'engineered' to the needs of the organisms in the environment in which they live. And you can determine that, within limits, by 'reverse engineering' the traits to see how they work [Dennett 1995: chapter 8]. Moreover, fitness exists over and above the properties of the individual organisms themselves. There are three debated ways to construe this. Fitness can be a relation of genes to other genes. Fitness can be a supervenient property - that is, it can be a property of very different physical structures (of ants, aardvarks and artichokes) [Sober 1984]. Or fitness can be seen as an emergent property, a property of systems of a certain complexity and dynamics [Depew and Weber 1995]. Whether fitness is a genetic, organismic or system property is a hot topic in modern philosophy of biology. I think the system interpretation is the way to approach it [Weber and Depew 1996, Depew and Weber 1995]. Recently, there have been attacks on the very notion of adaptive explanation by some evolutionary biologists themselves (eg, Gould and Lewontin [1979]). These fall into two camps - those who think adaptation is not enough to explain diversity of form, and those who think that adaptive explanations require more information than one can obtain from either reverse engineering or the ability to generate plausible scenarios. The reason given for the former is a kind of argument from incredulity - natural selection is not thought to be a sufficient cause, and that macroevolution (evolution at or above the level of species) is a process of a different kind than selection within species. Arguments about parsimony (Ockham's Razor) abound. Arguments for the second view - that selective explanations need supplementing - rest not on the causal efficacy of selection (which is not denied) but on the problems of historical explanation [Griffith 1996]. In order to explain why a species exhibits this trait rather than that trait, you need to know what the null hypothesis is (otherwise you can make a selective explanation for both a case and its opposite equally well). Perhaps it has this trait because its ancestors had it and it has been maintained by selection. Perhaps it has it because it would be too disruptive of the entire genome and developmental machinery to remove it. Perhaps it has it for reasons to do with genetic drift, simple accident, or whatever. In order to make a good scientific explanation, says Griffiths, you must know a fair bit about the phylogeny of the species, its environmental distribution, and how the processes that create the trait work at the level of genes, cells and zygotes. This leads us to the question of what a scientific explanation really is; indeed, it opens up the question of what science is, that it is so different from other intellectual pursuits like backgammon, theology or literary criticism. ================= Is evolution science, and what does 'science' mean? Summary: science is not a simple process of falsification of hypotheses. The philosophy of science is not just the views of Popper, which have some real problems. Evolution can be falsified in the usual meaning in scientific practice. It is often argued, by philosophers and creationists alike, that Darwinism is not falsifiable, and so is not science. This rests on the opinion that something is only science if it can be falsified, ie, proven wrong, at least in principle. This view, which is due to Popper, is not at all universally accepted, and some history of philosophy is in order to make sense of it and the criticisms made of it.[note 1] At the time Darwin was formulating his view of evolution, the prevailing exemplar of science was the Newtonian program. Laws were paramount, and they determined the outcome. Science sought generalisations. Darwin tried to make a Newtonian science, and was hurt when the leaders of the field like Whewell and Herschel, two of his acquaintances and mentors, dismissed his theory as insufficiently like their model of science.[note 2] William Whewell was the first real philosopher of science. He was heir to the English and Scottish schools of empirical commonsense. He rejected Hume's notion that induction (proving a rule or law by reference to singular examples of data and observation) was not correct, even if he didn't deny the logical force of the argument, that you cannot prove a universalisation no matter how many pieces of evidence you have to hand. Whewell proposed what he called the 'consilience of inductions' - the more inductive cases you have based on data, the more reliable the generalisation. This is what Darwin tried to attain, and explains why he spent so many years gathering case after case to bolster his theory. He thought he was doing it the Right Way [Ruse 1979]. Another school of thought was Positivism . This view affirmed that the only true knowledge was scientific knowledge, and that only positively established proofs were scientific knowledge. This meant the positivists had to be able to distinguish between real science and the pseudoscience of phrenology, spiritualism and the other crank theories coming onto the scene during the nineteenth century. One positivist was the physicist Ernst Mach of Mach speed fame, and from him grew a school of thought in the German-speaking countries of Europe known as Logical Positivism, centering on Vienna. The Logical Positivists held that something is science when it can be verified, and they had all kinds of rules for that, based on Hume's dictum that whatever does not logically follow from matters of fact or number was metaphysics. This was equivalent to saying it was literally nonsense for the positivists. When it was observed that the Verification Principle was unverifiable, and so nonsense, the school fell apart. However it spurred the young Karl Popper [note 3] to put forward his own way of telling apart science (of which the exemplar was the new physics) from pseudoscience (of which the exemplars were Marxism and Freudianism). Popper also accepted the legitimacy of metaphysical statements, but denied they were any part of science. Popper's view was called 'Falsificationism', and held in its mature versions that something is scientific just so far as it (i) is liable to be falsified by data; (ii) is tested by observation and experiment, and (iii) makes predictions. Real Scientists Make Predictions. This was the True Scientific Method. A minor quibble should be dealt with - Popper knew that the Falsification Principle could not be falsified. It was openly metaphysical. In this context, it makes sense why a pro-evolutionist like Popper called Darwinism a metaphysical research program. It was no more falsifiable (he thought) than the view that mathematics describes the world, and it was just as basic to modern biology [Popper 1974: sect 37]. The spanner in the works was first thrown by sociologists and historians of science, including Robert Merton, and later Thomas Kuhn. Kuhn's book [1962] in particular set the cat among the pigeons. If Popper thought that what he was doing was distilling the essence of science into a set of proscriptions, Kuhn and others observed that no science in fact looks like this model. According to Kuhn, you can't even compare when one theory is better than another scientifically, for each global theory carries its own assessment methods. Change from one global theory to another is more akin to a conversion than a rational decision. Science only changes when the older theory can't cope with some arbitrary number of anomalies, and is in 'Crisis'. When this happens, the scientific community acts like someone looking at those dual-aspect pictures like the famous old crone/young woman picture. They 'snap' from one view to another, what Kuhn called a 'paradigm shift'. Science undergoes revolutions, and the only way to determine if something is scientific is to see what scientists do (there is an obvious circularity here). This was very popular in the relativistic late 60s, but ran up against some serious problems. For a start, nobody could find these radical revolutions in the historical record. Even Galileo and Newton turned out to be revisionists rather than revolutionaries. Then, 'paradigm' started to be used for every new theory with impact on a discipline (which is all theories, in the end). Eventually, it became obvious that while Kuhn had made many interesting observations, there was no such universal cycle as he had proposed in the 'life' of a scientific theory. The very term 'paradigm' was attacked as being too vague [Masterman 1970], and Kuhn eventually dropped it in favour of more restricted terms like 'disciplinary matrix' and 'exemplar' [Kuhn 1970, 1972]. Kuhn's friend Paul Feyerabend [1970a, 1970b, 1975] stirred things even more by arguing that there was no such thing as the Scientific Method, either, something Kuhn held to exist in a more philosophical sense. Feyerabend argued that method was restricted to small subdisciplines, and that at any point any scientists could bring in anything from astrology to numerology if it helped. He even cheered on early recent creationism. This was the extreme end of the 'science is what scientists do' approach. Feyerabend wanted scientists to do anything they wanted, and call it science. It was opposed by Imre Lakatos [1970], who argued that science was a historical series of research programs. So long as they were getting results, they were 'generating', otherwise they were 'degenerating'. According to Lakatos, a research program is a strongly protected core of theories that are relatively immune to revision, while ancillary theories are frequently revised or abandoned. One thing all three of these philosophers thought in opposition to Popper - there was no point that could be ruled off as the dividing line between 'rational' science and 'non-rational' non-science. Lakatos identified what he called the Duhem-Quine Thesis - nothing can be falsified if you want to make suitable adjustments elsewhere in your theoretical commitments. Get a result that upsets your favoured theory of gravitation? Then the instrument's in error, or something is interfering with the observations, or there's another process you didn't know about, or some other background theory is wrong. And the point of this is that all these moves are used - they are rational in the sense of good scientific practice. Positivism is irretrievably dead by this stage. So, what is the difference between science and non-science? There are several mutually compatible alternatives on the board. Pragmatism , the only philosophy to have originated in North America, holds that the truth or value of a statement like a theory or hypothesis lies in its practical outcomes. Pragmatists say that being scientific is a retroactive label given to what survives testing and makes a real practical difference, like a theory about a cancer affecting how that cancer is treated, more successfully. Progress in science is the accumulation of theories that work out [Laudan 1977]. Realists continue to say that what makes something scientific is its modelling reality successfully, and this has given rise to what is known as the Semantic Conception of Theories [Suppe 1975, see Ereshevksy 1991 for criticisms of this approach]. On this account, what science does is create effective models , and if a model meets Lakatos's criteria for a generating research program, those models are presumed to be adequate and true. And there is a sociological strain. This is divergent, but is either fully relativistic (science is just something that scientists construct for some social reasons of their own), or more pragmatist and realistic, and shares a strong commitment to the importance and uniqueness of science (eg, Hull [1988]). Back to evolution. It becomes clear why the simple-minded parroting, even by scientists, that if it can't be falsified it isn't science, is not sufficient to rule out a theory. What science actually is, is a matter for extreme debate. The rediscovery post-Merton of the social nature of science has thrown eternal Scientific Methods out the window, but that doesn't mean that science is no longer distinguishable from non-science. It just isn't as easy as one would like in an ideal world. Last I looked, it wasn't an ideal world, anyway. However, on the ordinary understanding of falsification, Darwinian evolution can be falsified. What's more, it can be verified in a non-deductive sort of way. Whewell was right in the sense that you can show the relative validity of a theory if it pans out enough, and Popper had a similar notion, called 'verisimilitude'. What scientists do, or even what they say they do, is in the end very little affected by a priori philosophical prescriptions. Darwin was right to take the approach he did.It is significant that, although it is often claimed that Darwinism is unfalsifiable, many of the things Darwin said have in fact been falsified. Many of his assertions of fact have been revised or denied, many of his mechanisms rejected or modified even by his strongest supporters (eg, Mayr, Gould, Lewontin, Dawkins), and he would find it hard to recognise some versions of modern selection theory as his natural selection. This is exactly what a student of the history of science would expect. Science moves on, and if a theory doesn't, that is strong prima facie evidence it actually is a metaphysical belief. [note 4] A final quote from Hull [1988: 7] is instructive: Yet another ambiguity constantly crops up in our discussions of scientific theories. Are they hypotheses or facts? Can they be "proved"? Do scientists have the right to say that they "know" anything? While interviewing the scientists engaged in the controversies under investigation, I asked, "Do you think that science is provisional, that scientists have to be willing to reexamine any view that they hold if necessary?" All the scientists whom I interviewed responded affirmatively. Later, I asked, "Could evolutionary theory be false?" To this question I received three different answers. Most responded quite promptly that, no, it could not be false. Several opponents of the consensus then current responded that not only could it be false but also it was false. A very few smiled and asked me to clarify my question. "Yes, any scientific theory could be false in the abstract, but given the current state of knowledge, the basic axioms of evolutionary theory are likely to continue to stand up to investigation." Philosophers tend to object to such conceptual plasticity. So do scientists -- when this plasticity works against them. Otherwise, they do not mind it at all. In fact, they get irritated when some pedant points it out. Most scientists are not philosophically inclined and will make use of whatever is a help in their work, but not in the way Feyerabend thought. Reflective scientists know that it's all how you ask the question that counts. Most physicists would not immediately think that atomic theory could be false, either. They are answering the question "is it likely to be dropped later on?" not the philosophical "could it in theory be dropped?" which is a different issue. Philosophers do conceptual tidying up, among other things, but scientists are the ones making all the sawdust in the workshop, and they need not be so tidy. And no cleaner should tell any professional (other than cleaners) how it ought to be done. Creationists who say, "evolution is not like what Popper said science should be, so it isn't science" are like the janitor who says that teachers don't keep their classrooms clean enough, so they aren't teachers. =============== Predictions and Explanations Evolution is sometimes criticised for not being a predictive science, and for not having natural laws. This relates to the issue of whether science should be like physics (see the section on the nature of science), but the two issues raise a more general matter. It goes to the question whether explanations have to make use of natural laws, and just what are explanations anyway? One theory about explanation is called the nomological deductive (ND) theory, or less pretentiously, the hypothetical deductive theory. Due to philosophers Karl Popper and GC Hempel [cf Dray 1966, especially the essay by A Donagan], it has the form: Premises Universal Law ============= Thing to be explained The idea is that if the thing to be explained is a logical, deductive, consequence of the premises and the universal laws, then you have explained it. Once you have a theory of this form, then you can predict that a phenomenon will occur if the initial conditions are right, based on the universal laws of physics, chemistry, etc: Initial Condition Universal Law ============= Observed Phenomenon The prediction is a deductive consequence of a true theory and proper measurements. Since evolution cannot make predictions of this kind, and in fact any outcome is compatible with the theory, its critics say that evolution is not a complete science (see the section on the tautology of fitness). However, there are problems with this highly idealised view of scientific explanation, and anyway, I will argue it doesn't affect evolution. Any set of laws are ideal simplifications. In order to predict where a planet is going to be in 10,000 years, you have to ignore may things, such as the very small bodies, the influence of distant stars and galaxies, friction due to solar wind, and so forth. And it works, to a degree. But that degree is still real. You may only be off a few meters, but you will be off, due to these ignored complications. Physical systems of this kind are stable, in that the initial conditions do not greatly affect the outcome. Evolution is not like these systems. It is highly sensitive to the initial conditions and the boundary conditions that arise during the course of evolution. You cannot predict with any reasonable degree of accuracy what mutations will arise, which genotypes will recombine, and what other events will perturb the way species develop over time. Moreover, the so-called 'laws' of genetics and other biological rules are not laws. They are exceptional. Literally. For every law, right down to the so-called 'central dogma' of molecular genetics, there is at least one exception. And yet, we know the properties of many biological processes and systems well enough to predict what they will do in the absence of any other influences. This is proven in the lab daily. So, in this way, we have in biology the extreme end of the continuum of what we have in physics at the other end. The difference is one of degree, not kind. And more and more, physicists are uncovering systems that are similarly unstable and sensitive. You cannot predict in physics what any small number of molecules will do in a flame, or in a large gas volume, for example. And while the weather cannot be predicted at all in fine detail for very long, you can explain last week's weather through the initial conditions and the laws of thermodynamics, etc, after it has happened. If you take the standard form of biological explanation, it has the same structure as a physical explanation. It just differs in two ways. First, you cannot isolate 'extraneous' influences ahead of time for wild populations. Second, you cannot make a prediction much beyond the immediate short term (hence, nobody can predict the future of evolution of a species). Although a number of experiments have been conducted to test selectionist hypotheses through prediction, such as the studies on finches in the Galápagos Islands by the Grants, mostly, explanations in evolution take the following format: Initial Conditions at t-n Properties of Biological Systems ================================ Observed Phenomenon at t In other words, they are retrodictions, not predictions. The only formal difference between this and the same form in physics is that the tense is different. This use of the nomological-deductive model in historical cases is called a covering law model [Dray 1957, 1966]. So, physics is not really a different kind of science to evolutionary biology, except in some matters of convenience with experimentation, and the degree of the stability of the systems it sometimes explains, and not always then. Covering law explanations can be used to retrodict the initial conditions, under certain circumstances. If you know what is now in evidence, and you have laws that generate these outcomes, you can sometimes predict what will be found: _Predicted Initial Conditions_ Universal Law ============= Observed Phenomena For example - you know that certain features of ants are derived (not in the primitive ancestor). You have general laws of evolution that account for the phenomena you observe (actual ants today, and in the fossil record). So, you predict that a certain transitional form will be found. When it is, you have made a bona fide prediction. What special conditions can this be done under? Well, for a start, if you have a deductive argument if A then B, you cannot immediately infer from the existence or truth of B, that A. It might have been something else. B might have a virtual infinity of possible causes. Before you can make a retrodiction like this, you have to narrow down the field. That is, you have to assume the validity of some theoretical models before you can make the retrodiction/prediction. On the other hand, if you make such a claim, and it pans out, you have certainly strengthened your model. Finally, note that the ND model is not sophisticated enough to capture everything important about scientific explanations. A good many scientific explanations rest not on laws but propensities, that is, likelihood to behave in a certain way. And many perfectly useful accepted scientific explanations are not deductive, they are inductive. That is, the likely outcome of the initial conditions and the laws is not a rigourous deduction but an induction with all the problems that brings. Still, that's what science does, whether philosophers like it or not (cf Franklin 1997). -- John Wilkins, Head of Communication Services, Walter and Eliza Hall Institute of Medical Research [Remove .UNSPAM from header address] It is not enough to succeed. Friends must be seen to have failed. - Capote