Friday, July 04, 2008

Reasons and causes of belief

Steven Law has an excellent (and long) post on Religion and philosophy in schools. He mentions a few topics that I'm moved to comment on.

Law gives a good account of the difference between reasons and causes for belief.

People’s beliefs can be shaped in two very different ways, as illustrated by the two different ways we might answer the question “Why does Jane believe what she does?”
First, we might offer Jane’s reasons and justifications – the grounds of her belief. Why does Jane believe our CO2 gas emissions are causing global warming? Well, she has seen the figures on how much CO2 we are putting into the atmosphere, and she has seen the graphs based on Antarctic ice cores showing how global temperatures have closely tracked CO2 levels over the last 600,000 years. So, concludes Jane on the basis of this evidence, the rising temperatures are very probably a result of our CO2 emissions. ...

So we can explain beliefs by giving people’s reasons. But this is not the only way in which beliefs can be explained. Suppose John believes he is a teapot. Why? Because John attended a hypnotist’s stage-show last night. John was pulled out of the audience and hypnotized into believing he is a teapot. The hypnotist forgot to un-hypnotize him, and so John is still stuck with that belief. ...

So we can explain beliefs by giving a person’s reasons, grounds and justifications, and we can explain beliefs by giving purely causal explanations (I say purely causal, as reasons can be causes too [see for example Davidson, 1963]).
Purely causal explanations range from, say, being hypnotized or brainwashed to caving in to peer pressure or wishful thinking. These mechanisms may even include, say, being genetically predisposed to having certain sorts of belief (it has been suggested by Daniel Dennett (2006) and others that we are, for example, genetically predisposed to religious belief).

As good as Law's explanation is, I think it can be improved upon.

We can make a rigorous distinction between reasons and "purely causal" underpinnings of belief. I wrote earlier on consensus, truth and reality, and I can expand on this idea. We can create a causal story of belief as well as a logical story. A causal story says that some truth q entails (directly or indirectly) that some person or people believe that p. A logical story says that some truth q entails that p. When the causal story and the logical story coincide, we can say that the belief in p is justified, and q is a reason to believe that p. When they do not coincide, when q entails that someone believes that p but q does not entail that p, then q is a purely causal underpinning for p.

For example, that a tree actually exists in my front yard is the basis for a causal explanation for my belief that a tree actually exists in my front yard. The causal story is that because the tree exists, it reflects light, some of which causes changes in my retina, which sends nerve impulses to my brain, etc. which causes me to believe that a tree exists in my front yard. It is also the case that any proposition entails itself, so that a tree exists entails that a tree exists, so the existence of the tree is both the reason and the cause of my belief.

Just matching some causal account to a logical account does not, however, get us out of the woods. There are always an infinite number of potential causal accounts. Since we directly experience only the tail end of these causal accounts, we cannot directly verify which causal account is correct. Our causal accounts always contain a lot of physics, some of which may be opaque. We do not know, for example, precisely how the changes in my retina physically causes my belief that I'm seeing a tree.

We might also say that Jesus rose from the dead caused some people's belief that Jesus rose from the dead (i.e. people saw him do so, wrote about the experience, etc.). The causal account matches the logical account, so that Jesus actually did rise from the dead is a reason to believe he did so.

We have a method for distinguishing between competing causal accounts: We can evaluate and compare different accounts on simplicity, i.e. Occam's razor. We can choose the simplest causal account for our beliefs as the best causal explanation, and then match the logical explanation to the simplest causal explanation.

That Jesus actually rose from the dead is not the simplest causal explanation for our beliefs. That it would have been physically possible for him to have done so conflicts with an enormous quantity of experiences that people generally stay dead when they die. These inconsistencies can be "fixed up", but only at the cost of introducing an equally enormous quantity of additional premises. At worst we have to assume that the regularity and consistency of our experiences is not caused by the regularity and consistency of the universe, that the consistency of our experiences is an illusion. This may be true, but when we have a perfectly good explanation that does not conflict with our day-to-day observations; an explanation that with many fewer assumptions gives us a rock-solid causal explanation for our experiences, the much more complicated causal account is easily dismissed.

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