Saturday, September 05, 2009


Orac has a post on motivated reasoning, and draws the right conclusion from the studies that have been done on it:

I'm just as human as any of the participants in this study. Indeed, any skeptic who thinks he or she is not just as prone to such errors in thinking is not a skeptic but suffering from self-delusion. The only difference between skeptics and non-skeptics, scientists and nonscientists, in this regard is that skeptics try to make themselves aware of how human thinking can go wrong and then act preemptively to try to keep those normal human cognitive quirks from leading them astray. Indeed, guarding against these normal human failings when it comes to making conclusions about the natural world is the very reason we need science and why we need to base our medicine on science. If we do not and if we further do not at every turn gird ourselves with science, skepticism, and critical thinking against pseudoscience and the need to belief, it won't be long before we are indistinguishable from what we oppose.

It is worth contrasting this self-critical notion of skepticism with the methodological notion found in Massimo Pigliucci's recent post on skepticism:

A skeptic in the modern sense of the term, let’s say from Hume forward, is someone who thinks that belief in X ought to be proportional to the amount of evidence supporting X. Or, in Carl Sagan’s famous popularization of the same principle, extraordinary claims require extraordinary evidence. In that sense, then, what I will call positive skeptics do not automatically reject new claims, they weigh them according to the evidence.

One of the fundamental problems with Pigliucci's post, I think, lies in failing to recognize that the reason skeptics are, as Pigliucci saus, 'lonely', is that this guarantees that one's skepticism is based not (as in Orac's version) on what we all share as human beings but on idiosyncratic notions of belief and evidence. In other words, he fails to recognize that the 'loneliness' is an artifact of understanding skepticism in this way. Hume (rightly) did not see his claim as a self-evident truth. He argues for it. His argument is based on his own controversial account of belief and evidence -- and, indeed, is based on the most controversial elements of it. It is this account of belief and evidence that gives it its meaning on the Humean page; remove the argument underlying it, you change the meaning. On every account of belief and evidence you can make sense of the claim that beliefs should have evidential support; on most you can make sense of the claim that beliefs should have the right kind of evidential support (which will vary depending on the type of belief). But accounts where you can make sense of belief being 'proportioned' to evidence, where that just does not boil down to one of these two other claims, are far from being the most common kind of account. And, what is more, if you start talking with skeptics about their underlying reasoning, you find that they don't agree with each other, either -- most skeptics do not have a strictly Humean account of belief and evidence and therefore, whether they recognize it or not, they do not agree with Hume when he makes the claim, but reinterpret the phrases in light of their own accounts of belief and evidence. A Bayesian, for instance, has already changed what counts as proportioning belief to evidence, and therefore changed the very position itself. Very few skeptics, asked what they mean by "Extraordinary claims require extraordinary evidence," would spontaneously put it in the odd terms Pigliucci does, in which null hypotheses are states pertaining to belief rather than (as most people would normally interpret them, if they would even think of them at all in this context) hypotheses formulated for the purpose of statistical testing, which are never 'proportioned' to the evidence at all (rather than simply not rejected on the basis of it). What they mean by proportioning belief to evidence will have to be something different from what Pigliucci means. And unlike Orac's notion, in which there can be a genuine commonality among very diverse positions, this way of characterizing skepticism leaves us with a lot of positions that are only verbally similar.

One of the things I find interesting about this is that it's a clear example of how very different a family of logically possible positions can look depending on what you take to distinguish that family from other families of logically possible positions. Given that the positions in question are complex things, there's nothing to prevent them both being true, in the sense that both are picking up on features actually found among forms of (modern) skepticism; but, likewise, there is nothing to prevent them from establishing diverse boundaries, so that there are groups who fall inside on one account but outside on another. This is as it should be, because the human mind is capable of generating that much diversity; but it's something we often overlook, to the detriment of our analyses.

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