Is Any Theory Empirically Adequate?
Can we know for sure that any theory is empirically adequate? To accept a theory as empirically adequate and set out to explain why is to generalise beyond the available evidence, to make an ‘inductive leap'.
But it is no different with explanation in science itself. Scientific explananda are typically general. Scientists typically seek to explain general statements, rather than statements of particular fact. For example, they seek to explain why sticks look bent when half-immersed in water, not why my walking-stick looked bent last Thursday when I dipped it in the Leith. Some radical inductive sceptics deny that any general statement is true. The best reply to them is to ask how they know this (self-refuting) statement to be true. Other radical inductive sceptics deny that any general statement can be known for certain to be true. The best reply to them is to agree, but to insist that some general statements can be rationally adopted as true. Scientists who set out to explain why sticks look bent in water obviously suppose that sticks do look bent in water... always. And it is reasonable for them to suppose this, despite the fact that it might turn out to be mistaken, as the inductive sceptics rightly point out. As in science, so also in metascience. Metascientists can reasonably suppose that a theory is empirically adequate, and set out to explain why. If the metascientific explanatory project is to be rejected because it involves an ‘inductive leap', then science's typical explanatory projects must be rejected on the same ground.Even so, to claim that a theory is empirically adequate is to make a very strong claim. It is to claim that all the empirical regularities predicted by a theory are true. There are both vertical and horizontal ‘inductive leaps' involved in such a claim. To say that any particular predicted empirical generalisation is true involves the vertical inductive leap from examined cases to all cases.
To say that all the predicted empirical generalisations are true involves the horizontal inductive leap from the generalisations we happen to have tested to all of the generalisations. So, what is to be explained, empirical adequacy, is already epistemically problematic. But let us set this aside. After all, we are dealing here with antirealists who think empirical adequacy an epistemically respectable category, but who baulk at truth.So, supposing that it makes sense to try to explain empirical adequacy, how exactly does truth do it? Suppose the theory in question asserts the existence of unobservable or theoretical entities. The theory will not be true unless these existence claims are true, unless the theoretical entities really exist, unless the theoretical terms really do refer to things. So part of the realist story is that T is observationally adequate because the unobservables it postulates really do exist.
But this cannot be the whole realist story. Reference may be a necessary condition for success, but it cannot be a sufficient condition. A theory may be referential yet false and unsuccessful (more on this later). The other part of the realist story is that what the theory says about the unobservables it postulates is true.
The Miracle Argument says, not just that truth explains empirical adequacy, but that it is the only explanation, or at least the best explanation. To evaluate this claim, we need to pit the realist explanation of success, in terms of successful reference and truth, against other possible antirealist explanations. What might such antirealist explanations be like? van Fraassen replaces truth by empirical adequacy as an aim for science. But it is obvious that we cannot satisfactorily explain the empirical adequacy of a theory in terms of its empirical adequacy:
T is empirically adequate.
Therefore, T is empirically adequate.
This explanation is no good because it is blatantly circular.
Other antirealist explanations are also circular, but not so blatantly circular as this one.
Laudan replaces truth by problem-solving ability as an aim for science. As he explains, an empirical problem is posed by a question of the form “Why G?”, where G is some empirical generalisation. So to say that a theory is a good empirical problem-solver is just to say that it yields lots of true empirical generalisations. So, when we unpack the definitions, what we have once again is an explanation of empirical adequacy in terms of empirical adequacy.Then there is Jarrett Leplin's surrealism, which is short for ‘surrogate realism' (Leplin 1993). Surrealism arises by taking some theory T and forming its surrealist transform T*: “The observed phenomena are as if T were true”. It is clear that “The observed phenomena are as if T were true” is merely a fancy way of saying that T is empirically adequate. That being so, we cannot satisfactorily explain the empirical adequacy of T by invoking the surrealist transform of T. For that is, once again, explaining empirical adequacy just by invoking empirical adequacy.
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