Chapter 7 of Timothy Williamson’s “The Philosophy of Philosophy” is an extended argument against “psychologising” evidence in philosophy. Before we can evaluate those arguments, it would be useful to get clear on just what it is to psychologise evidence. In this post I’ll say a bit about what that amounts to, and in the next post look a bit more carefully at Williamson’s text to see just what position he is attributing to his opponent.

In some ways the debate Williamson is contributing to is among the oldest in modern philosophy. Consider the following two positions about perceptual evidence, each of which has found many partisans over the last few centuries.

• Perceptual Evidence is Psychological. My perceptual evidence consists in facts about the psychological states I am in when undergoing a perceptual experience. So, for instance, my perceptual evidence might include that I’m visually representing that there is a table in front of me.
• Perceptual Evidence is External. My perceptual evidence consists in facts that I perceive. So, for instance, my perceptual evidence might include that there indeed is a table in front of me.

The psychological theory has a number of advantages. It can explain how people having illusory perceptions can get the same kind of evidence (albeit of lower quality) as people having veridical experiences. It arguably staves off certain kinds of doubts about our evidence, at least to the extent that we have privileged access to our psychological states. It explains the fact (if it is a fact) that when we get evidence in favour of some proposition p about the external world, we generally know what kind of evidence we have. It is unusual, that is, to get evidence that p, but not know whether that is visual evidence, or tactile evidence, or testimonial evidence, or whatever. If the evidence for p just is the visual or tactile or testimonial experience, that is easily explained. And it offers the prospect of an easy theory of evidence possession; a point I’ll return to below.

But there’s one big cost of the psychological theory: it seems to promote scepticism. There is a long tradition, starting in the modern period with Descartes, of proponents of the psychological view wondering how to get from psychological evidence to knowledge of the external world. And there is another long tradition, culminating at the present with Williamson, of opponents of the psychological view using this worry as a reason to start with evidence in the external world, and avoid this sceptical doubt.

The debate here is not confined to perception. We can have a similar debate in testimony. Imagine I am told that p by a trusted friend. I now have some evidence for p. What is it? One answer, similar in spirit to the psychological answer above, is that I’ve been told that p. Another answer, similar in spirit to the external answer, is p itself. The latter answer might be favoured by a theorist of testimony who thinks that when I get testimony from a trustworthy source, I simply receive the warrant they have for believing p. (The two answers here aren’t quite equivalent to the positions known as reductionism and anti-reductionism in the epistemology of testimony. Someone might be an anti-reductionist and hold that the telling, rather than what’s told, is the evidence, by holding that we don’t need any extra grounds to infer, on the basis of that evidence, that p. I’ll say more about such inferential rules in later posts.)

Both answers here are possible, but it is much more plausible to take the evidence to be the telling rather than what’s told. So we can use that as a relatively clear example of what happens when we take evidence to be something that supports an external world proposition p, rather than p itself. One consequence is that in reporting inferences, we can replace testimonial knowledge with knowledge that the testimony was made without making the inference worse. So imagine we know that if Celtic win today, they’re champions, and we’re told by a trusted friend that Celtic did indeed win. Then we might make either of the following inferences.

An inference from facts about football

1. If Celtic won, they are champions.
2. Celtic won.
3. So, Celtic are champions.

An inference from facts about testimony

1. If Celtic won, they are champions.
2. My friend said that Celtic won.
3. So, Celtic are champions.

The first is valid, while the second is not. But we are interested here in inferences, not implications, so that’s no disqualifying mark against the second inference. For the second has a virtue not shared by the first, namely that its premises are more secure. So it looks like the two inferences are equally good. And that suggests that the second inference really is just making explicit the inference that’s underlying the first.

We’ve now said enough to set up the interesting debate about philosophical evidence. Often we say things like Intuitively, that’s a cause of that, or Intuitively, that’s wrong and so on in philosophy. What kind of evidence are we appealing to here? Read the rest of this entry »

Posted by Brian Weatherson at 12:00 pm

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Some papers and stuff happening around the web.

• Errol Lord on non-indexical relativism
• Kenny Easwaran on the a priority of computer proofs
• An updated version of my Attitudes and Relativism
• A PDF version of the new version of Deontology and Descartes’ Demon
• Slides from a lecture on Intuitions and Philosophical Evidence

The theme of the lecture was that the case Williamson makes in The Philosophy of Philosophy against evidence being psychological states isn’t as strong as it might at first appear. I’ll be spelling out the themes of that in several blog posts over the next few days.

Update: I should add that many of the ideas in the lecture on evidence, and in the upcoming posts, came from conversations here at Arch{e’}, and especially a reading group on The Philosophy of Philosophy. The meeting on chapter 7 of the book, which I’m mostly writing about here, was led by Daniele Sgaravatti, and his comments were especially useful.

Posted by Brian Weatherson at 12:00 pm

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The Inter-University Workshop on Philosophy and Cognitive Science at the University of Zaragoza features work by and on an important philosopher. The workshop in May next year will be on my (once again) colleague Ernie Sosa, and I imagine it will be very good. Here’s the actual announcement.

The XIXth edition of the Inter-University Workshop on Philosophy and Cognitive Science will be held on May 18 and 19, of 2009, in Zaragoza, Spain, organized by the Department of Philosophy of the University of Zaragoza. The invited speaker will be Ernest Sosa, Board of Governors Professor of Philosophy at Rutgers University. In recent years Interuniversity Workshop invited speakers have been: A. Clark, M. Davies, D. Dennett, J. Fodor, F. Dretske, R. Millikan, T. Burge, J. Searle, J. Kim, C. Peacocke, F. Recanati, B. Stroud, J. McDowell, N. Block, and P. Carruthers. Professor Sosa’s published or forthcoming work takes up a broad range of issues in epistemology, such as foundationalism/coherentism, internalism/externalism, reliabilism, contextualism, skepticism, the Pyrrhonian problematic and the problem of easy knowledge, epistemic normativity, intuitions and their place in philosophy, epistemic agency, epistemic virtue or competence, the epistemology of disagreement, testimony and social epistemology, the nature of knowledge, and the value of knowledge. The Organizing Committee invites contributions based on topics related to that work. (Some of it is available for downloading at his website.) Extended drafts (not less than 2000 words) should be sent to the coordinator of the workshop, Jesús Ezquerro, before February, 27, 2009 (e-mail only). Authors of accepted papers will have their accommodation, but not travel, expenses covered.

Posted by Brian Weatherson at 2:07 pm

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