Tuesday, February 24, 2009

Darwin was wrong?

This past Wednesday witnessed a debate between Rutgers’ own Jerry Fodor and Philip Kitcher on the merits of the theory of evolution by natural selection. What was unusual about this debate, as compared to others on the same topic, was that neither participant was anti-science, anti-reason, or pro-God. However, Jerry holds the iconoclastic (for a materialist) view that “the theory of evolution by natural selection is either false or vacuous, depending on how you read it.” Them, as they say, is fightin’ words.

I don’t want to resurrect that debate here. I went to the debate not to see arguments, but to watch people yell at Jerry (Tim Maudlin memorably said “Jerry, you accuse adaptationists of committing the intentional fallacy, while you yourself commit the fallacy of saying something is false when it’s been demonstrated right in front of you!”) However, I think it’s sad that no-one gives Jerry a sympathetic ear, because he’s a smart guy and even if he’s wrong, I think it would be a big advance in human inquiry just to know exactly why he’s wrong. So I want to explain what Jerry didn’t explain in the debate, though often adverted to: the analogy that Jerry sees between Chomsky’s argument against Skinner and Jerry’s argument against Darwin.

Part I of the analogy: Chomsky vs. Skinner

Most people, I imagine, have no idea what Jerry means when he says his argument more or less is Chomsky’s argument. We all thought that Skinner was wrong because, I don’t know, natural language syntax is recursive. But that’s not what Chomsky says in his review of Verbal Behavior (at least not in the selections reprinted in the Block anthology), so it’s worth taking a look at what Jerry sees in the review.

Simplifying a little, Skinner’s theory of learning by operant conditioning is that if an animal’s behavior B in situation S is reinforced (let’s just say “rewarded” for the time being), then the animal will learn to do B in S. For example, if a rat is rewarded for bar-pressing when shown a red thing, the rat will learn to press the bar when shown a red thing.

It’s an interesting fact that every finite set of red stimuli will share (that is, the members of the set will share) infinitely many properties other than being red. For instance, suppose the rat is presented with a series of bright red triangles in the bar-pressing experiment, when we want to enforce the behavior of bar-pressing given a red stimulus. The red stimuli here are not only red, but also closed figures; triangles; bright things; isosceles triangles; Granny’s favorite shape; triangles in a cage; things in a cage; etc. In addition, some infinite subset of these properties will be locally correlated with redness. That is, it might be true, in the rat’s environment (the cage), that something is red if and only if it’s a triangle; that something is red if and only if it’s an isosceles triangle; etc. Of course, not all the properties shared by the stimuli will be locally correlated with redness: ‘thing in a cage’ is true of both the red stimulus and the white rat. But an infinite amount of correlations is correlations enough. Call this “the ubiquity of local correlation.”

Now suppose we condition the rat in the way proposed. A bright red triangle is flashed, and when the rat presses the bar, it is rewarded with a food pellet. Question: can we use Skinner’s theory of learning by operant conditioning to tell us what the rat has learned? Answer: no—the theory construed in one way is false; in another way, it’s vacuous. Let’s investigate why.

A Skinnerian might be tempted to say: the rat has learned to press the bar when presented with a red stimulus. But in saying this, we need to ask her a further question, namely: is ‘learn’ here an intensional or an extensional verb? We (philosophers) say that ‘learn’ is extensional, if it follows from ‘Rat R learned to perform action A given a stimulus that is S’ and ‘S is locally correlated with F’ that ‘Rat R learned to perform action A given a stimulus that is F.’ That is, is it equally true to say that the rat learned to press the bar when presented with a red stimulus AND learned to press the bar when presented with a triangular stimulus AND learned to press the bar when presented with a stimulus that is an isosceles triangle AND…?

Let’s suppose the behaviorist says ‘yes,’ that ‘learn’ is extensional as used in her theory. Then the theory is clearly false. In order to show that the theory is false, we need only decouple two correlated variables and try the experiment again. Suppose we train the rat as described and then present it with a dull blue circle. Since ‘closed regular geometric figure’ had been locally correlated with ‘is red’ during conditioning, the rat, we are supposing, has learned to press the bar given a stimulus that is a closed regular geometric figure. A dull blue circle is a closed regular geometric figure, so the behaviorist predicts bar-pressing behavior. Now, maybe the rat will and maybe the rat won’t press the bar. If it doesn’t, behaviorism is falsified. If it does, behaviorism is left standing. But it won’t take long for a clever graduate student to find some or other local correlation the rat isn’t sensitive to (unless the rat learned ‘press the bar given any stimulus at all’), and we would all be well-advised to just abandon behaviorism now.

Horn II of the dilemma: suppose the behaviorist says ‘no,’ that ‘learn’ is not extensional as used in her theory. That is, the behaviorist asserts that the rat has learned to press the bar given a red stimulus, but that it does not follow from this and the fact that redness is locally correlated with property P that the rat has learned to press the bar given a P-stimulus. We ask: is the theory of learning by operant conditioning capable of predicting what the rat has learned, in the non-extensional sense of ‘learn’? NB. By this question we do not mean ‘is it possible to determine what the rat has learned?’ for if the rat has indeed learned anything, of course this is possible. We want to know what the theory in question has to say about what the rat learned.

Well, again, suppose we condition the rat as described, by rewarding it for pressing a bar in the presence of a bright red triangle. Has the rat learned (in the non-extensional sense) to press the bar given a red stimulus, a bright stimulus, a triangular stimulus, or some other kind of stimulus? Notice that the theory of learning by operant conditioning does not give us any guidance. The stimuli were all of these things. The experimenter receives no helpful advice from the theory about what hypothesis to hold.

Now suppose we test some hypothesis, say, the hypothesis that the rat learned to press the bar given a red stimulus. We present the rat with a blue triangle. If the rat does not press the bar, we have some confirmation of our hypothesis; if it does press the bar, perhaps we will be led to instead propose that the rat learned to press the bar given a triangular stimulus. This is how science goes. But the question is: is Skinnerian learning theory confirmed by any of this? And the answer is: vacuously, yes. If the rat does not press the bar, the Skinnerian will say ‘look, we were right: the rat’s bar-pressing behavior was rewarded when the rat was given a red stimulus, and it learned to press the bar when given a red stimulus.’ If the rat does press the bar, the Skinnerian will say: ‘look, we were right: the rat’s bar-pressing behavior was rewarded when the rat was given a triangular stimulus, and it learned to press the bar when given a triangular stimulus.’

We can go on. After the first decoupling experiment, the experimenter will have ruled out a certain hypothesis, say, that the rat learned to press the bar when presented with a red stimulus. But there will still be infinitely many properties locally correlated with triangularity, so it will not follow that the rat learned to press the bar when presented with a triangular stimulus. Here again, Skinnerian learning theory is of no help whatsoever in constructing hypotheses about what the rat learned. It cannot predict, it can only incorporate empirical findings post-hoc into the behaviorist model.

So the theory of learning by operant conditioning (a) makes no predictions (b) does not guide researchers in formulating hypotheses about learning and (c) is trivially compatible with any outcome whatsoever. That is not how science goes.

This is how I’ve heard Fodor present Chomsky’s case against Skinner. And I think it’s a compelling case. The claim is that the theory of learning by operant condition is false, if ‘learn’ is read extensionally and trivially true if ‘learn’ is read intensionally. And I take it that no-one wants to defend Skinner at this point. So without further ado:

Part II of the analogy: Fodor vs. Darwin

[Every sentence of this section should really begin with ‘According to Fodor, as I understand him.’ Please don’t attack me for attacking Darwin; I am not attacking Darwin. I am presenting Fodor’s views, as I understand them.]

Simplifying a little, Darwin’s theory of evolution by natural selection is that if two heritable traits T and T’ are possessed by some ancestral population in some ecological environment, and T is more fit than T’, then T will increase in prevalence in the population over time, eventually moving to fixation (except in certain cases where the fitness of T depends on prevalence of T’). For example, suppose there is a population of brown bears that live in the arctic wastes. At some point a mutant white bear arises. Since coat color is heritable, and a white coat is more fit than a brown one, whiteness moves to fixation in the bear population.

It’s an interesting fact that every finite set of whiteness phenotypes will share (that is, the members of the set will share) infinitely many phenotypic properties other than whiteness. For instance, suppose that at present 20% of the bear population possesses the whiteness phenotype (and for simplicity’s sake, suppose the bear head-count is 100 total individuals, so that 20 of them are white). The white bears will not only be white, but also bears; four-legged; the same color as snow; the same color as paper; more closely related to one another than to any non-white non-parental bear (assuming that whiteness is a dominant trait); located in some perhaps-disjoint spatio-temporal region; etc. In addition, some infinite subset of these properties will be locally correlated with the whiteness phenotype. That is, it might be true, in the bears’ environment (the arctic), that something is a white bear if and only if it’s a bear the same color as snow; that something is a white bear if and only if it’s more closely related to white bears or its parents than non-white non-parental bears; etc. Of course, not all the properties shared by the whiteness phenotype will be locally correlated with it: ‘bear’ is true both of white bears and of brown ones. But an infinite amount of correlations is correlations enough. This is another instance of the ubiquity of local correlation.

So suppose a mutant white bear arises in the population. Question: can we use Darwin’s theory of evolution by natural selection to tell us why the phenotype moves to fixation in the population? Answer [again, Fodor’s answer, not mine]: no—the theory construed in one way is false; in another way, it’s vacuous. Let’s see why one might think this is so.

An adaptationist might be tempted to say: the whiteness phenotype moved to fixation because being white increased the probability that a bear would produce viable offspring as compared to the probability that a brown bear would produce viable offspring. But in saying this, we need to ask her a further question, namely: is ‘phenotype P increases fitness relative to competing phenotypes C’ an intensional or extensional context at position P? It’s an extensional context if it follows from ‘phenotype P increases fitness relative to competing phenotypes C’ and ‘phenotype P is locally correlated with phenotype Q’ that ‘phenotype Q increases fitness relative to competing phenotypes C.’ That is, if it’s an extensional context, it should be equally true to say that the whiteness phenotype increases fitness AND the same-color-as-snow phenotype increases fitness AND the being-located-in-region-R (where R is the region containing all and only white bears) phenotype increases fitness AND...

So let’s suppose that the adaptationist does indeed say that ‘phenotype P increases fitness relative to competing phenotypes C’ is extensional at the P-position. Then the theory is clearly false. In order to show that the theory is false, we need only decouple two correlated variable and see what happens in the population. Suppose, to take a flight of fancy, that we’re super-scientists capable of making snow brown (we’re already capable of making it yellow, so this shouldn’t require too much of a technical advance). The adaptationist told us that ‘the same-color-as-snow phenotype increases fitness’ and by this she also meant that ‘the white phenotype increases fitness.’ Now we change the color of the snow to brown. Suppose the brownness phenotype now goes to fixation. It looks like we’ve falsified adaptationism, for it is not true after all that whiteness increases fitness.

[If you don’t like the example, because you’re worried we’ve changed the ecology, which is a free variable we’d been suppressing, you should realize that I could have run the example with any of the local correlates of the whiteness phenotype. For example: the phenotype of being a bear with exactly 19 other individuals of the same color. We don’t have to even intervene at all to watch adaptationism get falsified, we can just let whiteness go to fixation. And if you think I’m cheating by using extended phenotypes, talk to Dawkins.]

Horn II of the dilemma: suppose instead that the adaptationist says that ‘phenotype P increases fitness relative to competing phenotypes C’ is not extensional (is intensional) at the P-position. That is, the adaptationist asserts that the same-color-as-snow phenotype in bears in their present ecology increases fitness, but it does not follow from this and the fact that the same-color-as-snow phenotype is locally correlated with the whiteness phenotype that the whiteness phenotype increases fitness in bears in their present ecology. We ask: is the theory of evolution by natural selection capable of predicting what heritable traits increase fitness among bears in their present ecology? NB. By this question we do not mean ‘is it possible to determine what heritable traits increase fitness’ for if some traits do and others do not, of course this is possible. We want to know what the theory in question has to say about the relative fitness of bear phenotypes.

So suppose the whiteness phenotype has gone to fixation and there are now, say, 200 white bears. Did the whiteness phenotype increase the fitness (in the intensional sense) of the ancestral white bears or was it rather the same-color-as-snow phenotype, the same-color-as-paper phenotype, or any other phenotype that the white bears happen contingently to share with one another and not brown bears? Notice that the theory of evolution by natural selection does not give us any guidance. The ancestral bears (and the present bears) were all of these things. The evolutionary scientist receives no helpful advice from the theory about what hypothesis to hold (though of course the scientist has a helpful set of priors, and is likely to latch on to the correct hypothesis, without invoking Darwin’s theory).

Now suppose the field scientist actually runs some controlled tests on the population of bears in order to test the hypothesis that it was the same-color-as-snow phenotype that increased the fitness of the bears in their ecology, relative to the competing different-color-from-snow phenotype. Perhaps she isolates some of the bears in an area where the snow has been made artificially brown, along with some other conspecific brown bears taken from a different population. If the brownness phenotype goes to fixation in this new population, we will have some confirmation for our hypothesis; if whiteness goes to fixation, we may be led to instead propose that the whiteness phenotype (rather than the same-color-as-snow phenotype) increased fitness (maybe females prefer white bears or something). This is how science goes. But the question is: is Darwinian evolutionary theory confirmed by any of this? And the answer is [again, Fodor’s answer, not mine]: vacuously, yes. If brownness goes to fixation, the Darwinian will say: ‘look, we were right: the same-color-as-snow phenotype was more fit than the whiteness phenotype, and it went to fixation.’ Similarly, if whiteness goes to fixation, the Darwinian will say: ‘look, we were right: the whiteness phenotype was more fit than the same-color-as-snow phenotype, and it went to fixation.’

We can go on. After the first decoupling experiment, the experimenter will have ruled out a certain hypothesis, say, that the same-color-as-snow phenotype was not fitter than its competitors. But there will still be infinitely many properties locally correlated with the whiteness phenotype, so it will not follow that that phenotype was fitter. Here again, Darwinian evolutionary theory is of no help whatsoever in constructing hypotheses about which traits increase fitness. It cannot predict, it can only incorporate empirical findings post-hoc into the adaptationist model.

So the theory of evolution by natural selection (a) makes no predictions (b) does not guide researchers in formulating hypotheses about evolution and (c) is trivially compatible with any outcome. That is not how science goes [or so says Fodor].

This, I take it, is an intriguing argument. It has nothing to do with God. The claim is that the theory of natural selection read extensionally is false, and read intensionally is vacuously true. Nothing about the tree of life is questioned, nothing about inheritance through genes, nothing about the physical basis of all observable phenomena. The hard work of evolutionary biologists in the field is not ignored, nor is it taken to be irrelevant. Fodor is merely arguing that for biologists to attribute their scientific findings on evolution to The Law of Natural Selection is rather like contemporary computational psychologists attributing their findings to Behaviorism. The findings are still there, and still correct: they’re just neither suggested nor explained by natural selection. Or again, so says Fodor.

Conclusion

I don’t know whether Fodor’s right or not. Maybe that makes me an idiot, because maybe he’s as obviously wrong as Randy (Gallistel) and Tim say he is. So be it. But I’d like to be very clear on why Fodor is wrong, if he is. I used to think he was just arguing: there are no biological laws; explanation is subsumption under a law; therefore there are no biological explanations. And I used to think the response should be: that’s an exceedingly narrow conception of explanation. But now I take his argument to be what I presented above: it’s about whether the theory of natural selection itself has any content whatsoever. And one can’t answer that challenge by modifying what one counts as explanation. I invite civil discussion in the comments. No Godbotting, plz.

38 comments:

  1. waw, i didn't follow everything, but i always enjoy when a (widely accepted) theory is shown to have problems...

    when was the fodor-kitcher debate? next time, please, put an announcement on facebook! :)

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  2. @mozandcats

    You're right, this should've been better promoted. I found out about it two days before it happened. But I will facebook next time.

    MJ

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  3. Hi Michael. Thanks for the very clear exposition of Fodor's argument. It's refreshing to see a presentation of the argument that doesn't confuse 'intentionality' with 'intensionality', and avoids peculiar locutions like 'intensional processes'. I think you're right that Fodor's argument at least promises to be more substantive than the "the theory natural selection doesn't provide law-like explanations" interpretation you mention at the end of your post (like you, I think the proper response to that argument is just: expand your conception of explanation). However, I'm not sure that the argument can ultimately make good on that promise. I have a few other problems with the argument that I'll register in due course.

    But first, I'll provide a quick gloss on (what I take to be your reconstruction of) Fodor's argument. I think it's clear that statements of the form 'phenotype T increases fitness relative to competing phenotypes' are intended to introduce intensional contexts, so I'll focus on the second horn of Fodor's purported dilemma, according to which the theory of natural selection (ToNS) is trivially true. That horn is supposed to go something like this: suppose we're trying to explain why trait T increased in prevalence (relative to traits T') in a given population over a given period of time. There are going to be indefinitely many properties, other than having T, that all the T organisms share but all the T' organisms lack. Call these the properties that locally co-occur with T. Now, there might be facts about whether having T, or any of the properties that locally co-occur with T, was actually causally efficacious in the relative increase in prevalence of T. But, Fodor claims, ToNS doesn't predict which of these properties, if any, was causally efficacious. So no matter which property turns out to have been causally efficacious, ToNS will be confirmed (or: will fail to be disconfirmed).

    Ok, that's more-or-less the argument. Here are my problems. First, there's a long-standing debate in the philosophy of biology about the 'units of selection'. Roughly, the debate is about what kinds of things get selected in the process of natural selection: whether genes, organisms, or what-have-you. One dominant position is gene selectionism: the view that, strictly speaking, only genes are selected. But if that's right, it's not clear how Fodor's argument gets off the ground. Suppose we're trying to explain why gene G increased in prevalence relative to alternatives. There will be all sorts of properties that locally co-occur with G, but these just aren't the sorts of things that are subject to selection (for the sorts of reasons that gene selectionists adduce).

    Second, one can make a similar move even if one doesn't want to commit oneself to gene selectionism. Suppose one holds that phenotypic traits, such as the white fur of polar bears, are bona fide units of selection. Now, let's suppose that having white fur locally co-occurred with having snow-colored fur over the course of polar bear evolution-- as well as with indefinitely many other properties. Fodor's central claim is that ToNS doesn't have the resources to distinguish between these various properties. But of course it does: remember that the targets of selection are, according to ToNS, *heritable* traits, and it seems to me that (say) having snow-colored fur pretty clearly is not a heritable trait. Evolutionary theorists might debate about precisely what gets selected, but they all agree that whatever it is, it's something heritable (indeed, the units of selection debate is precisely about what is properly said to be heritable).

    Third, let's bracket these concerns and concede for the sake of the argument that any heritable unit of selection will locally co-occur with indefinitely many other heritable units of selection over a given period of evolution. What follows? Fodor's argument apparently purports to show that ToNS per se, as opposed to any specific selectionist claim about the evolutionary trajectory of a particular population, is trivially true. But it's not at all clear to me that ToNS per se purports to be true simpliciter, or that it even makes sense to ascribe truth or falsity to ToNS. What might ToNS *assert*, such that it could be true or false? It certainly doesn't assert that all evolutionary change occurs via the process of natural selection; evolutionary biologists universally agree that natural selection is but one process of evolutionary change among many. Perhaps one might think that if ToNS is true of anything, it's true of some abstract system that, as it were, 'analytically' satisfies the principles of natural selection. Philosophers of science have said similar things about scientific models in general (see: Cartwright, Giere). In this case, Fodor would be right that ToNS is trivially true; but this wouldn't be an interesting conclusion about ToNS specifically, it would be a general point about the nature of scientific models (this is why I expressed skepticism at the outset about whether Fodor's argument ultimately amounts to anything more than a version of "ToNS doesn't provide universally true, lawlike explanations").

    Fourth, perhaps the emphasis of Fodor's conclusion is supposed to be not so much that ToNS is trivially true, but that it isn't falsifiable. Fodor says that if a heritable trait T increased in (relative) prevalence in some population, ToNS doesn't predict whether it was having T, or having any of the heritable traits that (by hypothesis) locally co-occurred with T, that was causally efficacious in increasing the prevalence of T. Thus, Fodor claims, ToNS is supported no matter which of these heritable properties in fact turns to have been causally (i.e. selectively) efficacious. But this just assumes what ToNS predicts, namely that some heritable property was in fact causally efficacious in increasing the prevalence of T. But, crucially, this needn't be the case: perhaps T increased in prevalence as a result of random genetic drift. Fodor is in effect saying that if a population underwent natural selection, the theory of natural selection will be true of it, hence the theory is trivially true. But of course a theory is trivially true of a hypothetical process that one stipulates it to be true of!

    Finally, on the issue of whether ToNS makes predictions: there's a reason we shouldn't use antibiotics unnecessarily, and it ain't because we can see the future.

    (Sorry for the overly long comment!)

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  4. @Alex

    Thanks for the comment. I am genuinely trying to get clear on these issues, and as usual, discussing them with smart people helps. Hence the blog.

    My first question for you is about heritability. You say that having snow-covered fur is not a heritable trait. But I would think that's bad for two reasons: one, it's *having snow-colored fur* rather than *having white fur* which is the reason the whiteness phenotype went to fixation. I assert this because the counterfactual "if the bears had had snow-colored fur, but not white fur, then they'd have been more fit than white bears without snow-colored fur" is true and the counterfactual "if the bears had had white fur but not snow-colored fur, then they'd have been more fit than those with snow-colored non-white fur." And the reason why the counterfactuals are relevant is that that's how you determine whether, say, it was night activity or their sable color that gave dark moths an advantage: you decouple the variables to find out what *would have happened* in different circumstances. So if "having snow-colored fur" is not heritable, then it seems as though heritability is not a constraint one wants on selectable traits.

    But I prefer the interpretation that one can inherit the trait "snow-colored fur." And my second reason is that I rather like the idea of extended phenotypes. Just as a parasite can have a "thick-shell" phenotype-- that is, because it causes its snail-host to have a thick shell, so too can a polar bear have a "same color as snow" phenotype-- not of course because it causes snow to be the color it is, but rather because the color snow is caused the bear to be the color of snow. Maybe I'm not thinking about these things right, but clarification would help.

    Final note: point taken. I didn't take heritability at all into account in my presentation of Fodor, and many of the phenotypes I describe (e.g. 'being a bear with exactly 19 other same-colored conspecifics') are obviously not heritable. So the argument would have to be fixed there. I still suspect that there will be an infinite number of heritable phenotypes locally correlated with the whiteness phenotype, but I should definitely reflect on why that is so, if it is.

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  5. Correction:

    Paragraph 2 should read: "...and the counterfactual 'if the bears had had white fur but not snow-colored fur, then they'd have been more fit than those with snow-colored non-white fur' is false.

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  6. @ Alex

    You say in your third point that you're not sure what it would mean to ascribe truth or falsity to the theory of natural selection, because everyone accepts that some non-adaptationist explanations are true. This seems wrong to me.

    The Skinnerian accepts that some cases of learning are not via operant conditioning. For example, I take it that Pavlov's dogs are not rewarded for salivating, nor punished for not salivating. But this doesn't mean that there's no sense to be made of saying 'Skinner's theory was true' or 'Skinner's theory was false'. His theory was that most learning in humans and animals was via operant conditioning (I take it; I haven't really read Skinner).

    I take it that the importance of Darwin is that (so we believe) most explanations of speciation are due to adaptation. The theory is true if that is so; false if, for example, most instances are explained by divine intervention (if that could even be an explantion... but you get what I mean).

    But: point taken. Even if many biologists would say or think that what Darwin's contribution was to science was that he explained most of the variety around us, it nevertheless might be so that evolutionary theory as reconstructed by philosophers of science gives ToNS a different role. But this really does push the debate into the realm of 'how does explanation work?' and 'what is a scientific theory?' and I'm not sure I know enough to have an informed opinion on such topics.

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  7. @Alex

    I wasn't sure if your final point was intended only as a comedic rebuttal, or also as an argument against Fodor.

    I take it that Fodor would respond: there are many solutions to every problem. If we used antibiotics unnecessarily, bacteria could respond by becoming resistant to antibiotics, or they could respond, for instance, by ceasing to subsist on humans. Or they could respond by dieing. All of these are consistent with ToNS. The reason why we suspect one response rather than another is not because ToNS is true, but because of things we know about the particular bacteria that infect and the chemical and physical reactions they have to antibiotics.

    I take your point of course: it does seem that there's a broader set of generalizations than just those given by the physics, but I don't yet quite see how to marshal that into an argument against Fodor.

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  8. Hi Michael,

    Thanks again for your comments. I think your first reply really gets to the heart of the matter, and serves to highlight where Fodor's thinking about these issues goes awry. Consider the elements of a selectionist explanation: a set of individuals that exhibit variation, and a 'filter' that disposes some variant-type to increase in prevalence relative to others. Fodor seems to think that it makes sense to individuate a variant-type on the basis of the filter that actually disposed that variant type to increase in prevalence. So, for example, he talks of the 'having fur the color of snow' phenotype, where it was (let's suppose) having fur the color of actual snow that disposed bears with that phenotype to increase in prevalence. Notice that (to put it crudely) Fodor here individuates *what* was selected on the basis of *why* it was selected. Now, if you think that's kosher, of course you're going to think that selectionist explanations are circular or unfalsifiable. To avoid circularity, selectionist explanations need some principled way of restricting what counts as a variant-type. But, of course, they have such a principle built-in: what counts as a variant-type depends on objective facts about what is heritable, facts that obtain *completely independently* of any facts in virtue of which a given variant-type was actually selected. This is, in effect, Darwin's crucial realization, and what distinguishes his theory of evolution from Lamarck's: Only heritable variation can be subject to selection.

    Anyway, that's all by way of me trying to get to grips with the underlying error that Fodor's making. Now let me address your specific points. First, there's a question about whether having fur the color of snow is a heritable trait. You suggest that it is by considering factors in virtue of which white fur was selected. But whether or not a trait is heritable has nothing to do with whether it in fact undergoes selection; plenty of heritable traits never get selected. Whether or not a trait is heritable depends on 'internal' facts about whether or not there are (to a rough first approximation) genes 'for' that trait, i.e. genes that play a specific causal role in the ontogenetic expression of that trait across a wide range of environments. Do white polar bears have genes for fur-the-color-of-snow? Aside from imaginary chameleon-like polar bears with fur that can change color to match the surrounding snow, they do not. They have genes that are (presumably) involved in the expression or inhibition of a certain follicular pigment: genes 'for' white fur, we might say (to summarize a complicated biomolecular process for communicative purposes). So having white fur was selected in polar bear evolution, not having fur-the-color-of-snow, because the latter isn't something that *could* have been selected, since it's not a heritable trait (in the polar bear lineage).

    Note that none of this precludes us from talking about extended phenotypes. We can perfectly well say that, for example, a certain type of spider's web is a heritable trait that might be subject to selection (or not, depending on the spider: variations in spider web design might just as well be due to environmental variation as to genetic variation).

    The point is just that for the purposes of selective explanations we need to individuate variant-types on the basis of whether the variant at issue is heritable, and this is true regardless of whether the variant is characterized by factors that extend 'beyond the skin' (in any case, the notion of the extended phenotype was developed in the service of gene selectionism; the idea is that, from the perspective of evolutionary theorizing, the the distinction between properties of organisms and properties of *products* of organisms is not theoretically interesting, since selection operates on genes, not organisms. But if gene selectionism is right, it's not clear how Fodor's argument gets of the ground).

    Finally, you're right that counterfactual reasoning plays a role in assessing claims about selection. However, its primary role is in distinguishing 'selection for' from mere 'selection of'. The idea that there's a 1-1 mapping between genes and traits is very wrong; for one, genes typically have lots of effects throughout the body. This means that some traits 'hitchhike' on others: they might be selected, but not selected *for* (i.e. they increase in prevalence, but not in virtue of any effects they have). Suppose that the gene that leads to white fur on polar bears (call it 'gene X') also leads to a taste for haddock, but that having a taste for haddock doesn't significantly impact polar bear fitness. Now, white fur and a taste for haddock are both heritable traits. But the former was selected for, while the latter just selected. Why? Well, if gene X had led to white fur but not a taste for haddock, it still would've increased in prevalence, whereas if it had led to a taste for haddock but not to white fur, it wouldn't have increased in prevalence (note that these possibilities needn't be remote: gene expression can be masked by all sorts of mechanisms).

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  9. You're right to pick on my third point; it wasn't as clear as it should've been. But note that my point wasn't that there's definitively no sense to be made of the claim that the theory of natural selection *simpliciter* (that is, prescinding from any specific selectionist claims) might have truth value. Rather, my 'point' was really a question: are there any available interpretations of this claim that will deliver Fodor's conclusion, namely that ToNS is trivially true? Your comment helpfully suggests one possible interpretation that I hadn't considered. You suggest that "the importance of Darwin is that (so we believe) most explanations of speciation are due to adaptation". Now, this isn't quite right: speciation happens for all sorts of reasons. But there is a point in the vicinity that is right: the theory of natural selection is the only explanation we have of complex adaptation. So one might be inclined to say that if ToNS (per se) is true, it's true of adaptation. But, as you point out, this is neither trivially true nor unfalsifiable. God might descend from the heavens tomorrow and inform us all that the purported 'evidence' for natural selection was put there to distinguish the true believers from the infidels. Fodor might nevertheless insist that the claim that the theory of natural selection is true of adaptation is trivial in the sense that it's *uncontroverisal* (at least, among rational, educated adults). But it's not clear what philosophical interest this claim has. Sure, the theory of natural selection is uncontroversial. So is heliocentrism. So what?

    ReplyDelete
  10. This is Michael. The previous comment was Alex Morgan. I'm posting his comments because of current weirdness in the commenting system. So please read "I" in the Feb 28, 2009 10:23 PM post just above this one as "Alex Morgan".

    MJ

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  11. Actually, there was a substantive point lurking beneath that final rhetorical flourish. Biologists warn that overusing antibiotics will lead to drug resistant bacteria. Medical practitioners heed their warnings, often at great material expense. I take it that Fodor would agree that all of this is perfectly reasonable behavior. But what makes it reasonable? The fact that the theory of natural selection allows us to predict that the overuse of antibiotics will lead to drug resistant bacteria.

    Now, Fodor is right that this predicted outcome isn't necessitated by the theory. There are a range of possible outcomes of overusing antibiotics that are consistent with the theory (though I think Fodor overstates the range of *plausible* outcomes. It really would be quite surprising if, for example, bacteria evolved a mechanism that allowed them to distinguish humans from non-humans). But there's a difference between outcomes that are *predicted* by a theory and outcomes that are merely *consistent* with a theory. Thermodynamics predicts that the sugar will dissolve in my coffee. But it is consistent with thermodynamics that the sugar *doesn't* dissolve in my coffee; it's just that this outcome is, according to thermodynamics, extraordinarily unlikely.

    As you suggest, Fodor might reply that what makes it likely that overusing antibiotics will lead to bacterial drug resistance is not the theory of natural selection per se, but rather our knowledge of particular facts about (e.g.) the molecular genetics of bacteria and the biochemistry of antibiotics. Taken broadly, this strikes me as false: we can use the theory of natural selection to make rough predictions about the consequences of overusing antibiotics, without knowing the biochemical details. Still, there's a shred of truth here: to make more detailed and reliable predictions, we must plug specific biochemical details into the parameters of a particular selectionist model. But using specific details as parameters in a model doesn't mean that any predictions made on the basis of the model are in fact *not* made on the basis of the model!

    It seems to me that what's going on here is just a general feature of scientific explanation. Consider an analogous case: I might use classical mechanics to predict that this missile will follow a parabolic trajectory. I might also plug specific facts about the mass of the missile, wind speed, etc., into the parameters of a particular model, and thereby make more precise and reliable predictions about the behavior of the missile. But even if I use these specific facts, I'm surely still using classical mechanics to make my prediction.

    Now, Fodor might well insist that we could *in principle* detach the theory of natural selection from background facts or beliefs about natural history and so forth, such that the theory, so denuded, makes no falsifiable predictions. He hasn't shown us how to do this, and the project strikes me as forlorn (it seems to me that it would fall victim to worries about the analytic/synthetic distinction). But the broader question is: even if we could denude the theory of natural selection from the background beliefs in virtue of which it has predictive power, why couldn't we do the same for *any* scientific theory? And if we could, why would that be philosophically interesting?

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  12. Even conceding everything Fodor thinks, doesn't natural selection on the non-extensional account still non-vacuously make predictions about, say, Twin Earth?

    That is, we would think that natural selection is wrong if we duplicated everything that is true about the situation except, perhaps, the H20-ness of water or that the planet's name is Earth rather than Smearth or, you know, whatever, and white bears didn't come to fixation. (Likewise with behaviorism and the red triangles.)

    Being pragmatist here for a moment: implicit in all scientific theories is a notion of relevant facts: the name of the planet is not relevant to (the particular case of) evolutionary adaptation, and so the theory predicts that if the name of the planet changes, the outcome of the evolutionary process does not. The fact that we can argue about what other facts are relevant (the color of the snow) doesn't change that.

    If we don't take that position, it's hard to see how this argument doesn't prove way too much, because it seems to want to cast all empirical science into doubt. After all, all scientific theories predict that some stimulus X will be followed by a response Y, and it's always possible to take an implausible extensional interpretation of X, decompose it into the various properties of X, and watch the theory blow up as Y doesn't happen. And it's likewise always possible to go the other way and talk about the impossibility of completely defining X apart from, in the kind of extreme holism that Fodor seems to be pushing, defining the whole world along with it.

    ReplyDelete
  13. Newton theorized: "A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force."

    We could attempt to prove this theory by applying a force to an object.

    However, there are infinitely vast number of objects that could be staying still - how to tell them a part?

    ReplyDelete
  14. @Anonymous

    Do you think this is somehow relevant to the debate? I'm missing the point.

    I will say that Newton told us how to tell them apart. It's in the rather famous bucket experiment. Tie a bucket to the ceiling and twist it around and around. Before you let go, the water is flat, and is not moving relative to the bucket. After you let go, the water is spinning relative to the bucket (because it's not moving but the bucket is) and is flat; soon the water picks up the momentum imparted to it by the spinning bucket and comes to be moving with the bucket, so that it's no longer spinning relative to the bucket. But now something curious has happened: the water is concave in the bucket. So at the beginning of the experiment, there was no relative motion between the water and the bucket, and the water is flat. Now there is no relative motion between the water and the bucket, and the water is concave. Newton argued that the difference was that during the experiment, the water was spinning relative to absolute space. Thus at least on some occasions we can distinguish absolute vs. relative motion.

    But all that's neither here nor there. If you think Fodor is just saying "infinitely many properties are selected, but how to tell which one evolution selected FOR?" then you're committing the ultimate philosophical sin of conflating your epistemology with your metaphysics. He's not making an epistemological claim. He's making a metaphysical claim about the explanatory status of generate-and-filter mechanisms, like operant conditioning and natural selection.

    ReplyDelete
  15. For those interested in Paul's comment, above, you can see more discussion at his blog Uncommon Priors.

    ReplyDelete
  16. RE: Fodor could be right!?

    Michael Johnson concludes above that “This, I take it, is an intriguing argument. It has nothing to do with God. The claim is that the theory of natural selection read extensionally is false, and read intensionally is vacuously true. Nothing about the tree of life is questioned, nothing about inheritance through genes, nothing about the physical basis of all observable phenomena. The hard work of evolutionary biologists in the field is not ignored, nor is it taken to be irrelevant. Fodor is merely arguing that for biologists to attribute their scientific findings on evolution to The Law of Natural Selection is rather like contemporary computational psychologists attributing their findings to Behaviorism. The findings are still there, and still correct: they’re just neither suggested nor explained by natural selection. Or again, so says Fodor.

    Although I haven’t fully analyze Fodor’s arguments on Darwin was wrong thesis, most critical readers of Darwinism would affirm Fodor’s endeavor in his critically analyzing of the history of science, especially of Darwinism, the one that has had been too much muddled by the neo-Darwinism reductionist Dawkinsism since the 1970s!?

    Best wishes, Mong 12/29/9usct1:44p; practical science-philosophy critic; author "Decoding Scientism" and "Consciousness & the Subconscious" (works in progress since July 2007), Gods, Genes, Conscience (iUniverse; 2006) and Gods, Genes, Conscience: Global Dialogues Now (blogging avidly since 2006).

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  17. ``Most critical readers of Darwinism''? By which you mean what? A tiny minority of commentators? I would aver that most critical readers of Darwin agreed with him. in the usual sense of critical. If by ``critical'' you mean those opposed to Darwin, well you may have a small point, and a subsequently even smaller conclusion. And such a vote means nothing, in any case. Just to make the point clear: I am a critical reader of Darwinism, and the more I read and critique, the better Darwinism looks. So, add that to your alleged poll. Critics of your logic can claim: ``at least one critic of Darwinism agrees with with it.'' And, as we have now invoked the existential operator, we are now free to say (via modern logic): ``some critical readers of Darwinism would NOT affirm Fodor’s rants.''

    ReplyDelete
  18. OK folks, try to keep things substantive.

    @Mong Tan:
    Of course everyone who is in good faith wants to consider all things critically, including ToNS (I personally don't like the label 'Darwinism'). But it is not nice to imply [the rather implausible claim] that the vast majority of evolutionary biologists who accept ToNS as a fact are not in good faith, and accept the theory uncritically. So please refrain from such veiled accusations in the future.

    @John
    Of course not everyone agrees with Fodor. To the best of my knowledge, no-one does, except Fodor himself, and perhaps his co-author (though I've heard reports to the contrary). I doubt many people are in a position to accept or reject Fodor's arguments, because they [the arguments] are so wilfully obscure (hence the post), but hopefully his new book will help clear things up. Nevertheless, you don't win arguments by calling the other side a "rant" and ignoring the substance of the debate.

    MJ

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  19. As an SF writer, I've always generally thought that all our theories are false, that time, new data and paradigms will eventually erode theories to the point where they are either overthrown or shown to be applicable in special cases. In this sense, Fodor seems to be stating the obvious: the argument, excellently summarised above, seems to be an elaborate illustration of the logical fallacies at the root of Darwin's natural selection theory. Well, yeah - and? Certainly there is some value in such an exegesis but I feel that I would be considerably more energised by a new and coherent theory. Nice try, though.

    ReplyDelete
  20. An interesting synopsis and discussion, much better than most of the back-biting from the old rivals and their take on Fodor I have come across.

    I think you have it correctly that the essence of Fodor's objection,not his argument, is does the ToNS explain much or anything at all?

    I take it to be part of how 'Evolutionary theory' in distinction from 'Evolution' show how organising principles in historical sciences are not explanations in the way that they suggest when the are called theories.

    I think though Darwin was more pluralist that Fodor makes out, he is correct in taking on the extreme adaptationists and 'Darwinists' but that is because they are wanting to do away with other 'explanations', which are also not explanations at all. I think as well there is some sense by which natural selection also means 'blind' and/or 'random' as if that means anything. Of course it does as against the 'designed' but not really getting at the problem. For all the rants against philosophy and philosophers and by philosophers too there is a timely reminder that a lot of the words used in these discussions as explanations just don't work clearly. It is a mess.

    I think it is wise to remember that there is loads of 'unnatural' or artifical selection, which Darwin himself ruminated upon, and inspired his thinking. Namely domestic breeding and 'genetic engineering' and all of the derivatives from his half-cousin Galton and Eugenics. I think Darwin's use of natural should be seen in this context of Victorian England and not just the design argument context which has unfortunately dominated much discussion.

    I think where the discussion about natural selection and adaptive evolution will become more interesting is in the artificial control of habitats and unintentional effect on habitats such as climate change and the tensions in the pluralist adaptive models of natural selection and artificial selection but that is nothing to do with Fodor's book.

    The Medea hypothesis challenging the Gaia theory is an interesting take on how we have to not rely on natural selection as the mechanism for human adaptation to habitat change but cultural selection for the 'desired habitat'. But I am meandering into confused areas.

    ReplyDelete
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  29. I see I am late to the party here, but I find the subject very interesting. I agree with Fodor that Darwinism is either false or vaccuous, depending on how you approach it, yet I was disappointed with his book and didn't really follow his logic.

    It doesn't help that I don't know much about Skinner or operant behavior, so the analogy was of no help. I would have done better if Fodor had explained Skinner by using the fallacies of selection as his starting point.

    ReplyDelete
  30. Alex, your final point that the evolution of bacteria proves the ToNS is as off base as the comment that Fodor has had selectionism demonstrated to him. Please keep in mind that Fodor is not denying evolution, so merely showing that evolution happens does nothing to counter him. He is claiming that selection is not helpful in explaining evolution.

    Hence, you would need to show how the bacteria gain the needed genetic changes when the need arises, and you would need to demonstrate that selection accomplished this rather than some other means of adaptation.

    My next message will address why the ToNS (Darwinism) fails logically, and is indeed either false or vacuous depending on how you read it.

    ReplyDelete
  31. Darwin's theory of selection is a logic fallacy and can't work. If the question is "How did the polar bear get snow-colored fur?" then to answer "selection" is false.

    If one is merely making the statement that if a bear gains a trait that makes it more likely to survive, then it is more likely to survive, then that is vacuous and tautologically circular. It is true, but non-explanatory.

    Assuming that one is trying to credit selection for a valuable trait, it should be easy to see that makes no sense. The trait must exist before the selection of it can take place, so chronologically it is impossible for the trait to be due to selection.

    Selection, like all filters, is subtractive only. It has only two options: Kill or not kill, but it can by no means create a new trait.

    The only part of Darwin's failed theory that can create anything at all is random happenstance, which is truly an efficent destroyer, not a creator. This means that to ascribe evolution to Darwinism is to say that all of earth's biota is a result of luck and nothing more. To add selection as a causal factor is a fallacy.

    Selection is nothing more than a poorly chosen term for not dying. It is false and illogical to claim that bears got a trait that helps it to not die by not dying.

    ReplyDelete
  32. Some say, ah, but what of artificial selection? Doesn't that create beneficial traits? Absolutely not.

    No type of selection can select anything that doesn't already exist. You can't select pigs that fly because no such thing exists. You could select bats that fly, but only because they already exist, and your selection of it didn't cause the trait.

    Selection is nothing but a silly logic fallacy as any second grader should easily be able to see right through. I'm not sure why it is so difficult for experts in philosophy to dissect and disprove.

    Selection can never cause a trait. Never has, never will. Darwin's foolishness is nothing but a much-hyped, yet demonstrably impossible Luck Theory.

    It is both false AND vacuous.

    ReplyDelete
  33. Sorry, but this statement by Alex is so wrong that I have to come back to it: "The fact that the theory of natural selection allows us to predict that the overuse of antibiotics will lead to drug resistant bacteria."

    The precise opposite is true: The fact that needed changes come along predictably only when needed is a crushing blow to the already flawed concept of Darwinism. If you can predict something, then it is NOT random, therefore we now know that Neo-Darwinists were wrong when they thought genetic changes were random.

    Moreover the weak concept that mathematical impossibility can be overcome by "millions of years" has been debunked. Evolution is both predictable and VERY fast acting when needed.

    If Darwin had been correct, then it wouldn't matter whether or not bacteria within us had ever been exposed to antibiotics. Need has no bearing on evolution, according to Darwin. Had Darwin turned out to be right, bacteria would already have the resistance, sitting there unneeded, but unharmful, for millions of years.

    We can predict specific beneficial genetic change when needed for the very reason that everything Neo-Darwinists have always told us has turned out to be wrong.

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