A summary of Lewis-Anscombe (at least in part)

 

            Lewis had originally argued that if naturalism/materialism is true, then all thoughts are produced by irrational causes, that is, the motions of atoms in the brain. Since atoms in the brain move the way they do because of the laws of physical and their original positions, if naturalism is true, then our beliefs would end up being no more likely to be true than false.

            We ordinarily distinguish between people who, to use Lewis's example, form the belief that the neighbor's black dog is dangerous by inferring it from evidence (they have seen it muzzled, messengers avoid the house), and people who form the belief that the dog is dangerous because they were bit by a black dog in childhood and have been terrified of black dogs since. One of these people is being rational, the other isn't. But, he argued, the real causes for everyone's beliefs, if naturalism is true, have to be blind physical causes, and therefore the distinction between people who form their beliefs rationally and those who don't breaks down. If naturalism is true no one ever believes anything for a reason, and if we are forced to assume that some people believe some things for a reason (which is certainly what scientists imply when they claim we should believe something because scientific evidence supports it), then we have to reject naturalism.

I think a lot of materialists would respond to this either by appealing to computers or appealing to evolution (though Lewis anticipated the argument from evolution). Anscombe does neither. She starts by distinguishing irrational causes from merely nonrational causes--she says that irrational causes are, basically, causal mechanisms that typically produce errors, while non-rational ones need not be shown to show that proclivity. However, to get an anti-naturalist result through this kind of argument is to confuse reasons-explanations with causal explanations. If someone gives an argument to the effect that the dog is dangerous based on evidence you can't rebut that argument by saying that the real reason the person believes the dog dangerous is because he was bitten in childhood. That's the fallacy that Lewis himself criticized as Bulverism, and is known in the logic books as the ad hominem circumstantial fallacy.

            However, Anscombe then considers the response that what Lewis is claiming is that if naturalism is true, then, as a matter of actual fact, logic and evidence are never relevant to the actual production of any belief, because a full explanation of every belief can be produced in terms of physical, not rational causes. However, full explanations for every event are simply explanations that answer completely what we want to know about the event. And if I ask for why you believe something I am asking for grounds, not causes, what I want is what I get if I ask you why you believe something. Casual laws are based on observed regularities, but reasons are elicited from people when you ask why they believe something or did something. Wittgensteinians typically held that reasons weren't causes at all, and that Wittgensteinian position seems to be built into Anscombe's response to Lewis.  Naturalism, Anscombe says, just says we can have causal explanations for all our thoughts in terms of causal laws, but that doesn't mean, as Lewis implies, that there are no reasons. One way of looking at this would be to say that talk of reasons and talk of causes occur in different language games, so there is no real conflict.

I maintain that although Anscombe has provided an attack on an anti-naturalist argument, but a modern naturalist might not, or should not, be inclined to stand up and cheer. Naturalism, I maintain, is an attempt to provide a comprehensive ontology, it is committed to the idea that other non-scientific explanations have to be either absorbed into the universe of naturalistic explanation or eliminated. While anti-causalist theories of reasons were popular in the 50s and early 60s, most naturalists today, I think, would follow Donald Davidson in saying that reasons are causes. I once gave a paper on the Anscombe exchange at a faculty colloquium at a secular philosophy department. The consensus  was I had a good critique of Anscombe, but that Anscombe's criticisms of Lewis's argument weren't interesting.

 

        First of all, explanations, causal or not, have an ontology, and naturalism isn't just a claim about causal explanations, it makes ontological restrictions. If I explain the presence of presents under the Christmas tree in terms of the munificence of Santa Claus, I imply that Santa is real. If I explain my belief in terms of reasons, then I imply that reasons exist, whether that explanations is a causal explanation or not.

            They do maintain that a total causal story, from big bang to big crunch, can be given for every event, and that causal story is part of a closed and nonteleological system. Lewis asked,

But even if grounds do exist, what exactly have they got to do with the actual occurrence of the belief as a psychological event? If it is an event it must be caused. It must in fact be simply one link in a causal chain which stretches back to the beginning and forward to the end of time. How could such a trifle as lack of logical grounds prevent the belief’s occurrence or how could the existence of grounds promote it?

And Anscombe said “We haven’t got an answer” to the question Lewis asked here.