Duhem-Quine Thesis Popper

Duhem-Quine Thesis Popper-85
The claim that evidence underdetermines theory may mean two things: first, that the evidence cannot prove the truth of the theory, and second, that the evidence cannot render the theory probable.

The claim that evidence underdetermines theory may mean two things: first, that the evidence cannot prove the truth of the theory, and second, that the evidence cannot render the theory probable.

For instance, no finite amount of evidence of the form Aa can entail an unrestricted universal generalization of the form All A's are B.

Deductive underdetermination rests on the claim that the link between evidence and (interesting) theory is not deductive.

But this is scant consolation because, apart from the fact that in the long-run we are all dead, the convergence-of-opinion theorem holds only under limited and very well-defined circumstances that can hardly be met in ordinary scientific cases.

The alternative is to claim that prior probabilities have epistemic force because they express rational degrees of belief, based, for instance, on plausibility or explanatory judgements.

The subjective Bayesians' appeal to subjective prior probabilities (degrees of belief) accentuates rather than meets this challenge.

Bayesians typically argue that, in the long run, the prior probabilities wash out: even widely different prior probabilities will converge, in the limit, to the same posterior probability, if agents conditionalize on the same evidence.Since theories entail observational consequences only with the aid of auxiliary assumptions, and since the available auxiliary assumptions may change over time, the set of observational consequences of a theory is not circumscribed once and for all.Hence, even if, for the time being, two (or more) theories entail the same observational consequences, there may be future auxiliary assumptions such that, when conjoined with one of them, they yield fresh observational consequences that can shift the evidential balance in favor of it over its rivals.Underdetermination is a relation between evidence and theory.More accurately, it is a relation between the propositions that express the (relevant) evidence and the propositions that constitute the theory.That is, the evidence can raise the probability of a theory.So inductive underdetermination must rest on some arguments that question the confirmatory role of the evidence vis--vis the theory.A total denial of the legitimacy of any prior probabilities would amount to inductive skepticism.Inductive underdetermination would be inductive skepticism. The more interesting version of inductive underdetermination does not challenge the need to employ prior probabilities, but rather their epistemic credentials.In fact, given the fact that two or more rival theories are assigned different prior probabilities, the evidence can confirm one more than the others, or even make one highly probable.The challenge, then, is this: Where do these prior probabilities come from?

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