Thursday, March 12, 2009

Evolutionary theories of mind

An evolutionary theory of mind is not just a theory that minds have in fact evolved. Rather, it is a theory that it is essential to mindedness that one be the product of selection (natural or artificial). For instance, one may be an evolutionary theorist of mind because one thinks that intentionality must be understood in evolutionary terms, or because one is a functionalist and thinks that the notion of "proper function" that functionalism needs must be grounded in selective facts, or because one thinks that mental states have normative conditions (e.g., "neural state n is a believing that p only if it is the case that n should occur only if p"). An evolutionary theorist of mind is already willing to bite quite a bullet. Take Davidson's swampman: lightning strikes a swamp, and an exact physical duplicate of Davidson by chance comes out. Since there was no selection, the swampman is not a person, though he is exactly like Davidson physically. Of course if one were a dualist, one wouldn't be surprised by this, since the swampman could differ from Davidson in respect of soul, but the evolutionary theorist of mind doesn't believe in souls. The evolutionary theorist of mind is willing to bite the bullet on the swampman.

Here is an argument against evolutionary theories of mind. As it stands it is an argument against theories on which selection is metaphysically necessary for mindedness, though one might be able to do more with the argument. Moreover, the argument may well apply to other evolutionary analyses of concepts.

The argument is a reductio. Start with the following two theses:

  1. (Evolutionary theory of mind.) If none of the physical entities existing in a spacetime region U are the products of selection, there are no physical minds in U.
  2. (Almost global supervenience of physical minds.) Suppose worlds w1 and w2 are exact physical duplicates, except in an impotent region R of spacetime. Then w1 contains a physical mind outside of R if and only if w2 contains a physical mind outside of R.
Here, a "physical mind" is a mind entirely constituted or implemented by a purely physical system. A region R of spacetime is "impotent" provided that no event or substance in R can affect anything outside R.

Now for our clever construction. Imagine a world w1 which contains a planet much like earth, where history looks pretty much like it looks on earth, and which also contains a Great Grazing Ground (GGG), which is an infinite (we only need: potentially infinite) impotent region. Moreover, by a strange law of nature, or maybe the activity of some swampaliens, whenever an organism on earth is about to die, it gets hyperspatially and instantaneously transported to the GGG, and a fake corpse, which is an exact duplicate of what its real corpse would have been, gets instantaneously put in its place on earth. (I will call it "earth" for convenience but I shan't worry about its numerical identity with our world's earth.) Furthermore, there is no life or intelligence outside of earth and the GGG. Moreover, the organism dies as soon as it arrives in the GGG.

Our world's earth has minds, and the earth in w1 has a history that is just about the same. The only difference is that all the deaths of organisms occur not on earth but in the GGG, because they get transported there before death. But this does not affect any selective facts. Thus, the evolutionary theorist of mind should say that the situation in w1's earth is similar enough to that on our earth that we should say that w1's earth contains minds.[note 1]

The hard work is now done. For imagine a world that is exactly like w1 outside of the GGG, but inside the GGG, immortal and ever-reproducing aliens rescue each organism on arrival, fixing it so it doesn't die, and even make the organism capable of reproduction again. Furthermore, they do the same for the organism's descendants in the GGG. The GGG is a place of infinite (at least potentially) resources, with everybody having immortality and reproduction, with the aliens shifting organisms further and further out to ensure their survival.

Now in w2, there is no selection: Nobody ever dies or ceases to reproduce.[note 2] Thus, by (1), there are no physical minds outside the GGG in w2—all the earthly critters are zombies. But by (2) there are physical minds outside the GGG in w2, because w2 is an exact duplicate of w1 outside of the GGG. Hence we have absurdity.

Suppose our evolutionary theorist of mind denies (2). Then we have the following absurdity: It is up to the aliens in the GGG to determine whether or not there are physical minds outside the GGG, by deciding whether to rescue the almost dead organisms that pop into the GGG. But how can beings in an impotent region bring about that there are, or are not, physical minds outside that region? That would be worse than magic (magic is presumably causal).

Furthermore, while the numerical identities of the organisms on earth in w1 and w2 might depend on their history, they surely do not depend on what happens in the GGG, since the GGG is impotent. So we may actually suppose that the earthly organisms are numerically the same between w1 and w2. Thus, outside the GGG, w1 and w2 are exactly the same physically, and have exactly the organisms, but some of these very same organisms (say, Fred or Martha) have physical minds in w1 and do not have physical minds in w2.

This is truly absurd. Hence, evolutionary theories of mind should be rejected.[note 3]


larryniven said...

I am not following this at all. Where do you get the idea that "in w2, there is no selection"? That contradicts your own premise: if w2 is exactly like w1 near its Earth and if w1's Earth is enough like our Earth to have selection, it clearly is not the case that there is no selection in w2. There may be no selection in w2's GGG, but so what? In other words, what makes you think you get to use (1) where U is the entire universe?

Alexander R Pruss said...

Selection requires the differential transmission of genotypes based on the fitness characteristics of phenotypes. There is no differential transmission of genotypes in w2, since all genotypes get transmitted.

larryniven said...

You mean, there's no difference in the transmission of genotypes in w2's GGG. Again, on w2-Earth, you say it's exactly like w1 which in turn is very much like our Earth, which features differential transmission of genotypes quite prominently.

Alexander R Pruss said...

In the world at large, there is no difference. In other words, genes are transmitted, but in different locations. I don't differential locatedness is enough for this to count as natural selections. Footnote 2 in my post deals with this issue.

larryniven said...

Well, yes and no. Your footnote - 3, by the way, not 2 - describes an incredibly watered-down account of selection. All selection is local, whether you think so or not. Indeed, the entire point of evolutionary selection is that it's directed by local pressures. You try - unsuccessfully, by the way, but let's not go into that here - to remove all such pressures inside the GGG, but there is no similar removal of pressures from the Earth-like regions - right?

But okay - I'll keep reading. The point, it looks to me, is that you're skeptical about a theory of mind that relies on "a big nasty mess." I was under the impression, however, that this is precisely what evolutionary theories of mind are. Their proponents might not agree with that particular verbiage, but I really don't think you'll surprise anybody with the conclusion that minds can only evolve through a very complicated series of events. So if you're hoping to bait people into your contradiction by warning them that the only way out is to accept a "nasty" story about how minds evolved, it ain't gonna work. If anything, you ought to get rid of that footnote altogether if you want this argument to convince anyone, because it literally hands them a way out of your scenario.

Roger said...

Actually providing an account for an evolutionary theory of mind doesn't seem to be the primary concern most of the time, much less a story that is demonstrable or intellectually compelling. It really seems to get as far as, 'We don't know, but we have minds so it must be possible, because the alternatives are unthinkable.'

Though I like Alex's playful development so far. At the very least it starts to draw attention to the problems of an evolutionary theory of mind. Even if people bite the bullet and accept those problems.