Monday, December 05, 2005

Response to Ricky on Purely-Speculative Explanations

This is a response to Ricky's comment on my earlier post 'Perceptual/Cognitive Models Made From Purely-Speculative Explanations'. The comment said:

Interesting article. However, to my mind speculation, even pure speculation as you call it, doesn't necessitate the complete absence of evidence. Rather, speculation is usually performed on the basis of inconclusive or insufficient evidence rather than no evidence at all. Claims made in the total absence of evidence are more closely tied to blind faith or madness. I think most dictionary definitions of the word speculate would agree with this.
Ricky, thanks for taking a critical eye to the post. Though I agree that people tend to associate the term speculation with the notion of speculating on the basis of some limited or inconclusive evidence, at the same time, I think the concept of speculation is compatible with, and includes, situations where there the speculation is not being made on the basis of any evidence.

I had a look at what the Merriam-Webster dictionary says, and I think it does cover cases where there is no evidence for the speculation. There are three relevant meanings (there's a fourth meaning, but it has to do with business risk):
1 a : to meditate on or ponder a subject : REFLECT b : to review something idly or casually and often inconclusively
...
1 : to take to be true on the basis of insufficient evidence : THEORIZE
2 : to be curious or doubtful about : WONDER <speculates whether it will rain all vacation>
To me these are compatible with having zero evidence for the speculation. You can mediate or ponder on -- or 'to be curious or doubtful about' -- the cause of a phenomenon without having any evidence that the speculative cause is the actual cause. Having zero evidence is the limiting case of 'to take to be true on the basis of insufficient evidence'.

I think one severe limitation of my post was that I didn't make clear enough what I meant by 'evidence' for an explanation. It's a very difficult matter. (I actually think that the evidence for a belief is really a matter of the more general issue of justifications for beliefs, and what the strengths are of different sorts of justifications in different sorts of situations).

One thing I would try to clarify regarding evidence, is that I mean evidence for that points out that the explanation really is the explanation. I think you can make some distinction between between evidence that it is the correct explanation, and information that makes it appear a good or compelling explanation. Whenever there is some phenomenon to be explained, there are always a number of potential explanations, and evidence for a particular explanation is something that actually points to it as the one that is actually true.

For example, say there is some lettuce on the table has been eaten, and there are a number of possible explanations for this. You might believe that the pet rabbit ate the lettuce, and you might back this up with the claim that rabbits like lettuce. It might be true that rabbits like lettuce, but it's not really evidence that the rabbit actually ate the lettuce. Hmm, I'm not sure whether this example really clears things up, but I don't really have time to try to better what I mean.

There's a transitive condition here, as it's easy to have "evidence" which itself is just pure speculation with no evidence for it.

And while it may be difficult to say what constitutes evidence, sometimes it is quite clear cut that there is no evidence, or at least that there is none according to some standard of what constitutes evidence, which the person with the belief may even claim to accept.

One other thing about my original post - although I presented a pretty negative take, on purely speculative explanations, I should also have mentioned that they aren't bad per se -- they're bad when the belief holder doesn't realised or won't admit that the belief is purely specultive. Sometimes they are necessary. When you're trying to explain a phenomenon, you may come up with some explanations that are, at least initially, purely speculative. But of course, the next task is to see whether there is any evidence for or against them.

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