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Originally Posted by Original Position
I might just be misinterpreting you, but it seems to me that you are misrepresenting the proposed role of abduction in theory choice (at least, you are certainly de-emphasizing its importance in a way I disagree with). It doesn't add new evidence (but then, neither does deduction). Nor is it only relevant for coming up with hypotheses. What it does is make more explicit the criteria we use to decide between theories. Say we have two competing hypotheses: Intelligent Design versus the modern evolutionary synthesis. How do we decide between them?
We don't use deduction: both theories are internally consistent. We can't really use induction--famously, Intelligent Design has almost no empirical predictions. So what is our basis for preferring the modern evolutionary synthesis?
I would say it is abduction. That is, we have developed certain criteria that we think are characteristic of good explanations--things such as simplicity, scope, testability, and the other things zumby mentioned. When we compare these two theories to see which of them exhibit more of the virtues of a good explanation, the evolutionary theory is a clear winner. And thus, we accept it as the better theory.
Now, this isn't a proof (in the deductive sense) that Evolution is true and Intelligent Design is false. It could certainly be the case that what seems to us to be the better explanation is in fact false (an example of this would be the geocentric theory in ancient times). But it does give us a good reason to accept one theory over another.
Sure - and the reason the IDers dont accept it (and in fact claim
theirs is better or "abductively reasoned") is because they use differing criteria. We have no recourse other than to declare they are applying the standards incorrectly - once we start
demonstrating that logically or calling on further experimental support for our position/interpretation we are back to deduction and inference. (Where we belong).
When I said "seems reasonable to me" I
wasnt suggesting all these criteria arent applied. I was suggesting that the way we weight them, which ones take precedence and even whether they are satisfied is inherently subjective (I've heard theists say God is a simplifying explanation, for example). The extent to which we can
determine these things is as far as deduction and inference will take us.
Without empirical/rational testing of the competing hypotheses, there is nothing objective about which of the plethora of "hypotheses people find reasonable" should be preferred. We can doubt IDers are being honest, of course. But that's not really going to get us anywhere.
The number plate example is illustrative of the problem, I think. As is General Relativity. Remember that this came up in asking for support of a proposition's truth - I would very much like to see an explicit abductive argument for the truth of some proposition where (without any further empirical/rational test) the claim becomes more reasonable after the argument is presented.
I havent seen one.
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Now, it is true that abduction can also act as a spur on to more empirical work. We might think that a hypothesis is simple and elegant, but has little empirical support. If it were competing with another hypothesis that is less simple and elegant, but with greater empirical support, we have a dilemma. One way to resolve the dilemma is to seek for more empirical support for the more elegant hypothesis.
I dont think abductive reasoning is used in this 'compare the hypotheses' way. (That's certainly not the way I was introduced to it twentyish years ago). Why bother when we have empirical testing?
