Draft paper for comments
Here’s a draft paper written after my radio thing with Plantinga. Work in progress. Alvin has been kind enough to comment so it will be revised in light of that…
Plantinga’s Latest EAAN Refuted
In “Content and Natural Selection” (PPR forthcoming) Plantinga presents a version of his Evolutionary Argument Against Naturalism that he then bolsters to deal with a certain sort of objection.
The EAAN itself runs as follows. Let N be the view that there’s no such person as God or anything at all like God (or if there is, this being plays no causal role in the world’s transactions), and E be the view that our cognitive faculties have come to be by way of the processes postulated by contemporary evolutionary theory. Then, argues Plantinga, the combination N&E is incoherent of self-defeating. This, he maintains, is because if N&E is true then the probability that R – that we have cognitive faculties that are reliable (that is to say, produce a preponderance of true over false beliefs in nearby possible worlds) –is low. But anyone who sees that P(R/N&E) is low then has an undefeatable defeater for R. And if they have such a defeater for R, then they have such a defeater for any belief produced by their cognitive faculties, including the belief that N&E.
But why suppose P(P/N&E) – that is to say, the probability of R given N&E – is low? Plantinga supports this premise by means of a further argument. He begins by asserting that
materialism or physicalism is de rigeur for naturalism… A belief, presuming there are such things, will be a physical structure of some sort, presumably a neurological structure. (p2)
According to a proponent of naturalism, then, this structure will have both neurophysiological (NP) properties and semantic properties. However, it is, claims Plantinga, exceedingly difficult to see how its semantic properties could have any causal effect on behaviour. This because the belief would have the same impact on behaviour were it to possess the same NP properties but different semantic properties. So, claims Plantinga, N&E lead us to semantic epiphenomenalism (SE). But if semantic properties such as having such and such content or being true or false cannot causally impinge on behaviour, they cannot be selected for by unguided evolution. Truth and falsehood will be, as Plantinga puts it, invisible to natural selection. In which case, (on the modest assumptions that, say, 75% of beliefs produced must be true in order for a cognitive mechanism to be reliable, and that we have at least 100 such beliefs) P(R/N&E&SE) will be low.
In “Content and Natural Selection”, Plantinga attempts to deal with an objection to the above argument. The objection runs as follows: suppose content properties just are NP properties. That’s to say, suppose that reductive materialism (RM) is true. Then, because NP properties cause behaviour, and semantic properties just are NP properties, so semantic properties cause behaviour. But if semantic properties cause behaviour, then they can be can be selected for by unguided evolution. As we have just seen, Plantinga’s argument for P(R/N&E) being low is that SE is likely given N&E, and SE in combination with N&E makes R unlikely. But if our adherent to N&E also accepts RM, then they no longer have grounds for supposing SE is likely. Indeed, SE is actually rendered unlikely by the addition of RM. In which case, whether not P(R/N&E) is low, there’s no reason to think that P(R/N&E&RM) is low. In fact, as unguided evolution can and will now favour true belief, there are no grounds for supposing P(R/N&E&RM) is high.
Plantinga’s argument that P(R/N&E&RM) is low
So runs the objection. Which brings us to the heart of Plantinga’s argument in “Content and Natural Selection”. Plantinga argues that adding RM to N&E does not, in fact, make the probability of R high.
According to Plantinga, while RM does indeed allow semantic properties to have causal effects on behaviour (because they just are NP properties), the combination N&E&RM gives us no reason to suppose that the content of belief/neural structures resulting in adaptive behaviour are likely to be true. Suppose the belief/neural structure resulting in a piece of adaptive behaviour has the content q. While the property of having q as content does now enter into the causal chain leading to that behaviour, it doesn’t matter whether it is true:
What matters is only that the NP property in question cause adaptive behaviour; whether the content it constitutes is also true is simply irrelevant. It can do its job of causing adaptive behaviour just as well if it is false as if it is true. It might be true, and it might be false; it doesn’t matter. P10.
But if the NP property can do its job of causing adaptive behaviour just as well whether its content be true or false, true belief cannot be favoured by natural selection. In which case (PR/N&E&RM) is low.
Plantinga goes on to consider various other philosophical theories of mind that might be supposed, in conjunction with N&E, to make R likely, namely non-reductive materialism, Dretske’s indicator semantics, functionalism and Ruth Millikan’s biosemantics. Plantinga argues that on none of these theories does N&E render the probability of R high. He suggests intimates that there is a pattern to their respective failings,such that we can see that nothing like these theories will be capable of doing the job of making R probable given N&E.
Refutation of Plantinga’s argument
I shall focus here on Plantinga’s argument that, even given the addition of RM, N&E is still unlikely to produce cognitive faculties favouring true belief. There is, to seems to me, a fairly obvious flaw in this argument.
Let’s concede that what unguided evolution favours, in the first instance, is adaptive behaviour. As to what causes that behaviour, evolution doesn’t care – true beliefs, false beliefs, something else, it’s all the same to evolution. It’s only the result – adaptive behaviour – that is preferred. That is why Plantinga supposes unguided evolution is unlikely to select for cognitive mechanisms that favour true beliefs.
But even if unguided evolution doesn’t care what causes adaptive behaviour, just so long as it is caused, it does not follow, given further facts about belief, that if belief content causes behaviour, then the content in question is no more likely to be true than false.
The further fact about belief to which I now draw attention is this: that there exist certain conceptual constraints on what content a given belief can, or is likely to, have given its causal relationships both to behaviour and other mental states, such as desires
Consider a human residing in an arid environment. Suppose the only accessible water lies five miles to the south of him. Our human is desperately thirsty. My suggestion is that we can know a priori, just by reflecting on the matter, that if something is a belief that, solely in combination with a strong desire for water, typically results in such a human walking five miles to the south, then it is quite likely to be the belief that there’s water five miles to the south (or the belief that there’s reachable water thataway [pointing south] or whatever). It is highly unlikely to be the belief that there’s isn’t any water five miles to the south (or isn’t any reachable water thataway), or the belief that there’s water five miles to the north (or thisaway [pointing north]), or the belief that there’s a mountain of dung five miles to the south, or that inflation is high, or that Paris is the capital of Bolivia.
I don’t say this because I am wedded to some particular reductionist, materialist-friendly theory of content of the sort that Plantinga goes on to attack in “Content and Natural Selection”, such as Dretskian indicator semantics or functionalism or whatever: I’m not. Such theories may build on the thought that such conceptual constraints exist. But they suggestion that there are such constraints does not depend on any such theory being correct. True, perhaps content cannot be exhaustively captured in terms of its causal role, as functionalists claim. But that is not to say that there are no conceptual constraints at all on what the content of a given belief is likely to be, given the causal links that belief has to behaviour and other mental states such as desires.
What Plantinga overlooks is that, assuming NP is true and beliefs are neural structures, one cannot, as it were, just plug any old belief into any old neural structure willy-nilly. A neural structure that, in combination with a powerful desire to drink water, typically causes one to go to the tap and drink from it is hardly like to be the belief that inflation is running high, that Paris is the capital of Bolivia, or that water does not come out of taps. Among the various candidates for being the semantic content of the neural structure in question, being the belief that water comes out of taps must rank fairly high on the list. Even if we acknowledge that some other beliefs might also typically have that behavioural consequence when combined with that just that desire, the belief that water comes out of taps must at least be among the leading candidates.
But then we have grounds for supposing that, given we are likely to have evolved powerful desires for things that help us survive and reproduce, such a water, food and a mate, we are also likely to have evolved cognitive mechanisms that favour true beliefs.
Unguided natural selection will favour the adaptive behaviour of walking five miles south to find water if one strongly desires a water, but that adaptive behaviour will be caused by that desire in combination with a belief, and the belief in question is likely to be the belief that there’s water five miles to the south – a true belief, rather than the belief there’s no water five miles to the south – a false belief. True, there are other candidates for being the content of the belief in question. Indeed, they may be more likely candidates. Suppose our human has no conception of miesl or of south. Then, instead of being the belief that there’s water five miles south that causes his behaviour, it may be the belief there’s reachable water thataway. Either way, notice that the likely candidate for being the content of the belief in question is still content that is true.
So, my suggestion is that Plantinga overlooks significant conceptual constraints on what content can, or is likely to be, possessed, by a given belief, given it’s role in producing, in combination with desires for things that enhance our ability to survive and reproduce, adaptive behaviour. Once these conceptual constraints are acknowledged, it no longer looks unreasonable to expect N&E&RM to produce cognitive mechanisms favouring true belief. Indeed, given N&E&RM makes it likely that we will we have strong desires for things that enhance our ability to survive and reproduce, surely R starts to look quite probable.
What is P(R/N&E&NRM)?
I mentioned above that Plantinga also argues that the probability of R given N&E and non-reductive materialism (NRM) is also low. His argument is much the same as for the probability of P(R/N&E&RM) being low.
Plantinga considers a variety of non-reductive materialism on which beliefs are neural structures, but the semantic properties of those beliefs/neural structures strongly supervene on their NP properties. On this version of NRM, necessarily: a neurological structure exemplifies a given semantic poperty if and only if it exemplifies a certain NP property.
Plantinga argues that on R&E&NRM, the probability of R is still low. Suppose a belief/neural structure causes a piece of adaptive behaviour. The belief/neural structures semantic properties will follow from its (presumably adaptive) NP properties. But even if the NP property is adaptive, that gives us no reason to suppose that the supervening semantic content is true. If the content property involves false content, says Plantinga, “that won’t in the least compromise the adaptivity of the NP property.” p14 Thus, on N&E&NRM, the probability of our having cognitive mechanisms that favour true beliefs must still be low.
But again, Plantinga has overlooked the fact that there are significant conceptual constraints on what the belief content of a given neural structure can be, given its causal and/or logical relationships to behaviour and other mental states. A belief that, in conjunction with a powerful desire for water, typically causes subjects to walk five miles south is surely quite likely to have the belief content that there is water five miles to the south. It’s hardly likely to be the content that there’s water five miles to the north. A belief with the latter content will, in conjunction with a strong desire for water, typically lead subjects to walk five miles north, where, if their belief is false, they may well die of thirst. Thus, on N&E&NRM, natural selection will tend to favour neural structures/beliefs possessing NP properties that (because of the supervenience relation holding between them) in turn necessitate content properties the content of which is, in fact, true.
It seems, then, that in combination with either RM or NRM, N&E renders the probability of R high. Adherents of naturalism and evolution that subscribe to either RM or NRM, once they reflect a priori on the conditions under which a belief is likely to have such and such content,
Anticipating two replies
I now anticipate two responses Plantinga might make in response to the above argument.
1. Why assume we will evolve to desire for things that enhance our ability to survive and reproduce?
First, Plantinga may question my assumption that unguided evolution is likely to equip us with desires for things that enhance our ability to survive and reproduce, such as water, food and a mate. Plantinga may ask, “Why should evolution favour such desires?” Why should it not select other desires that, in conjunction with false beliefs, nevertheless result in adaptive behaviour?
In support of this suggestion, Plantinga may resurrect an argument that featured in an earlier incarnation of the EAAN, an argument I call the belief-cum-desire argument. According to Plantinga, for any given adaptive action (action that enhances the creatures’ ability to survive and reproduce), ‘there will be many belief-desire combinations that could produce that action; and very many of those belief-desire combinations will be such that the belief involved is false ’. p. 4
Plantinga illustrates like so:
So suppose Paul is a prehistoric hominid; a hungry tiger approaches. Fleeing is perhaps the most appropriate behavior: I pointed out that this behavior could be produced by a large number of different belief-desire pairs. To quote myself: ‘Perhaps Paul very much likes the idea of being eaten, but when he sees a tiger, always runs off looking for a better prospect, because he thinks it unlikely that the tiger he sees will eat him. This will get his body parts in the right place so far as survival is concerned, without involving much by way of true belief… Or perhaps he thinks the tiger is a large, friendly, cuddly pussycat and wants to pet it; but he also believes that the best way to pet it is to run away from it … or perhaps he thinks the tiger is a regularly recurring illusion, and, hoping to keep his weight down, has formed the resolution to run a mile at top speed whenever presented with such an illusion; or perhaps he thinks he is about to take part in a 1600 meter race, wants to win, and believes the appearance of the tiger is the starting signal; or perhaps…. Clearly there are any number of belief-cum-desire systems that equally fit a given bit of behavior. p.5
So adaptive behaviour can be produced by numerous belief-desire combinations. As Plantinga points out, on many of these combinations, the belief in question is not true. But then similarly, on many of these combinations, the desire is not for something that enhances the organism’s ability to survive and reproduce (wanting to be eaten by a tiger is not such a desire, obviously). Why assume that unguided evolution will favour desires for things that enhance our ability to survive and reproduce, given that desires for things that provide no such advantage, when paired with the right sort of belief (irrespective of whether those beliefs are true or false), will also result in adaptive behaviour?
This belief-cum-desire argument is flawed. We should concede that any belief can be made it result in adaptive behaviour if paired off with the right desire, and that any desire can be made to result in adaptive behaviour if paired off with the right belief. It does not follow that unguided evolution won’t favour the development of a combination of reliable cognitive mechanisms with desires for things that enhance survival and reproductive prospects.
The reason for this (spelt out in more detail in my [reference withheld for purposes of anonymity]) is as follows.
When we begin to think through the behavioural consequences of a species possessing unreliable cognitive mechanisms, it becomes clear that in at least very many cases (i) unguided evolution cannot predict with much accuracy what false beliefs such unreliable mechanisms are likely to throw up, and (ii) worse still, there just is no set of desires with which the species might be hard-wired that will, in combination with the mechanism in question, make the behavioural consequences broadly adaptive.
To illustrate, consider a hominid species H much like us but that with unreliable cognitive faculties. Let’s suppose, to begin with, that these creatures are reason very badly. Rather than use reliable rules of inference, they employ rules like this:
If P then Q
(call this the FAC rule). What desire might evolution hardwire into this species that will render the behavioural consequences of the various beliefs generated by the FAC rule adaptive?
Notice first of all that an advantage of having belief producing mechanisms, as opposed to hard-wired (i.e. innate) beliefs, is that such mechanisms can produce generate beliefs depending on environment. Evolution will favour such mechanisms if, as the organisms environment changes, so too do its resulting beliefs, and in such a way that adaptive behaviour still results.
But now notice that unguided evolution cannot anticipate what novel environments our hominids will encounter, and what false beliefs they will, as a result of employing the unreliable FAC rule in those environments, acquire. In which case, unguided evolution cannot pre-equip species H with some innate desire or set of desires that will make the false beliefs the FAC rule might easily throw up result in adaptive behaviour.
Even if the species’ environment does not vary much, he FAC rule may be still be employed in all sorts of ways. Suppose hominid H1 reasons like so:
If jumping out of planes is not safe, jumping out of balloons is not safe
Jumping out of balloons is not safe
Therefore jumping of planes is not safe
Hominid H2 reasons thus:
If jumping out of planes is safe, jumping out of planes with a parachute is safe
Jumping out of planes with a parachute is safe
Therefore jumping out of planes is safe
Both hominids employ the FAC and both start with true premises. Will H2’s conclusion result in adaptive behaviour? Not if H2 is hard-wired with, say, a powerful desire to commit suicide. As a consequence, perhaps H2 would now unlikely to bother jumping out of a plane. However, that same hard-wired, species-general desire now makes it much more likely that hominid H1 will plunge to his death. There’s no desire or set of desires with which species H might be hard-wired that will simultaneously make all the various conclusions that might easily be generated by their adopting the FAC rule nevertheless result in adaptive behaviour.
Similar problems arise when we turn to the suggestion that we have unreliable memories. An unreliable memory has as output beliefs that differ significantly from those it has as input. Suppose species H is equipped with an unreliable memory. Supposing we want this unreliable faculty to produce adaptive behavioural consequences, with what desire or desires must the species be programmed? Again, given novel environments, how can unguided evolution predict what the input beliefs and output beliefs of the faculty will be? Moreover, what set of desires that will result in both the input and output beliefs of this unreliable memories producing generally adaptive behaviour? If I learn that red berries are poisonous and grain is nutritious, but my unreliable memory later tells me red berries are nutritious and grain is poisonous, a desire to poison myself and avoid nutrition might render the output beliefs adaptive. However, those same desires, in combination with the input beliefs, will probably kill me.
The moral I draw is this. It is true that any false belief can, on any occasion, be made to result in adaptive behaviour if it is paired off with the right desire, and also that any desire (even a desire for something that hinders ones chances of surviving and reproducing) can result in adaptive behaviour if it is paired off with the right belief. However, it is not so easy to see what set of desires would make unreliable cognitive mechanisms of the sort we have been examining here result in adaptive behaviour. Indeed, it seems to me highly unlikely that a species will evolve unreliable mechanisms such as those described above, given there is no way to neutralize their otherwise maladaptive likely consequences with hard-wired desires. Unguided evolution is far more likely to produce reliable cognitive mechanisms in combination with desires for things that enhance our ability to survive and reproduce.
Perhaps Plantinga will suggest that I have cherry-picked my examples, and that there are still a great many candidate unreliable cognitive mechanisms that unguided evolution might easily select in combination with some appropriate set of hard-wired desires. I don’t believe that is the case. However, even if I am mistaken, the onus is surely now on Plantinga to demonstrate that unguided evolution is as likely to select unreliable cognitive mechanisms as reliable ones, given that, in the case of the FAC rule and unreliable memory, reliable mechanisms will surely be preferred.
2 Insist that beliefs cannot be, or are unlikely to be, neural structures
As we have seen, Plantinga’s EAAN, as presented in “Content and Natural Selection”, concedes the possibility that beliefs might just be neural structures, but then goes on to argue that, even if they are, the semantic properties of those neural structures cannot be selected for by unguided evolution. I have explained why I believe the latter argument fails. Given he existence of certain conceptual constraints on what belief any given neural structure might be, unguided evolution probably will select for true belief.
However, Plantinga could just drop the concession that beliefs might be neural structures. He has already indicated that it is a concession about which he has significant doubts. See for example footnote 4, where he says “It is far from obvious that a material or physical structure can have a content.”
However, this would be a significant retreat, and would change the character of the EAAN. The claim that neural structures cannot just be beliefs would now require some support. It would not be enough for Plantinga to say, “I can’t see how beliefs could just be neural structures”.
to be completed