To: Alistair L.
From: Geoffrey Klempner
Subject: Hume's theory of belief and the role of rationality
Date: 25th March 2010 12:24

Dear Alistair,

Thank you for your email of 19 March, with your essay for the University of London BA Modern Philosophy: Descartes et. al. module, in response to the question, 'What account did Hume give of the nature of belief? Can he provide a coherent account of why some beliefs are more rational than others?'

This is a great question which you have made a valiant attempt to answer, but I don't think that you do answer it satisfactorily.

The key question is why, if there is no rational basis for beliefs about cause and effect -- if all causal beliefs are themselves just the effects that the impact of information from the outside world has on our brains -- some of these 'effects' should be privileged above others as being more 'rational'? Belief isn't rational, period. It's just something animals and human beings have evolved in order to help us navigate our way through a perilous world.

Though notions of evolution or survival of the fittest are not explicit in Hume, he would no doubt readily assent to the idea that the utility of our natural disposition to believe, as in the case of non-human animals, is proved by its success. But that would hardly count as a definition of 'rationality'.

But, first, what is 'belief'? You cite Hume's definition of belief in terms of forcefulness, firmness, vivacity. I think it is important (especially in view of the above) to connect this to action. Hume recognized that it is the vivacity of ideas which moves us to act, and he gives as his reason that such ideas by becoming more vivacious acquire the same capacity to move us, physically, as the impressions of our senses. In this sense, beliefs are like perceptions at one remove.

I do think you could say a lot more about this than you have written in your answer. In a two part question you can assume that examiners will be looking for an equal effort in respect of each part (though this doesn't necessarily mean that you have to write the same number of words). It is important for the answer to the second question (the nature of rationality) that you give an adequate answer to the first (the nature of belief).

With regard to the second question, you cite a key piece of evidence in Section XV of the Treatise, 'Rules by which to judge of causes and effects'. A lot more could be made of this. Why should we agree to Hume's rules? If you conduct careful meteorological observations and conclude that there will be a storm tomorrow, while I consult sheep entrails, what makes your belief 'better' or 'more rational' than mine?

Perhaps an even better example, Hume's 'Dialogues Concerning Natural Religion' mounts an impressively powerful case against religious belief. Hume observes that human beings are 'credulous' and that we cling to beliefs for all sorts of irrational reasons. But why should we be persuaded by his arguments? This is especially pertinent given that beliefs regarding a deity are not put to the test of experience (or at least have not been up to now).

Hume was a supremely rational and clear-thinking philosopher. But what do we mean when we say that?

What the question is really asking you to do is derive a definition of rationality of belief which is consistent with Hume's account of impressions and ideas, and in particular his account of 'reasoning about causes and effects'.

A key piece of evidence is something you observe near the end of your essay: 'Feelings sourced from your emotions are relatively crude interpretations of the world that can provide the motivation to act without involving your reasoning faculties.' You go off somewhat at a tangent after making this remark. It is true that our emotions do have an important role in survival. But Hume isn't concerned with that. What he is concerned with is that our emotions lead us to believe all sorts of things which are not rationally based. The story of human credulity is the story about how easily our emotions are manipulated.

From this perspective, reasoning about causes and effects is the paradigmatic form of rational belief formation. The beauty of Hume's theory is that the rules for judging causes and effects are themselves the product of the very same process of formation of vivacious ideas through repetition of experiences. This is made possible by the human power of memory and language.

A dog cannot reason about causes and effects, it can only react to experiences. Whereas we have the ability to resist the impulsive response to an experience, through imaginatively placing the scenario in a wider context, where the belief in question forms part of a mosaic pattern of beliefs representing our acquired knowledge of the world. It is language, and through language, logic, which enables the formation a system of beliefs, connected by relations of justification or inference to the best explanation.

That is not a bad explanation of rationality. Will it do? Is Hume's account ultimately coherent? I leave that for you to decide.

All the best,

Geoffrey