Explications and Empirical Revision

In what senses are explications open to empirical revision?

Say you have a term t and an explication of that term t`. For instance, t could be “heat” and t` could be “mean kinetic energy”. Or t could be “volume” and t` could be “amplitude”. Or t could be “more probable than” and t` could be “has a greater limiting relative frequency than”.

One obvious sense in which the explication t` could be empirically revised is that we could have some theory T1 in which t` occurs essentially, and then, in light of new empirical evidence, we replace T1 with some theory T2 in which t` does not occur. For instance, we could have a Newtonian mechanical theory, in which “heat” is explicated with a certain definition of “kinetic energy”, and (loosely speaking) the evidence could suggest that we replace it with a relativistic theory, in which the definition changes. Or the evidence could suggest that some classical theory of statistical mechanics be replaced by a quantum mechanical theory, in which (so I understand) the frequentist explication of "probability" is not appropriate.

Another slightly stronger sense in which t` could be empirically revised would be this. Suppose we have some theory T, containing the term t, then we replace every occurrence of t in T with the explication t`, producing the theory T`. Then, since T is presumably more vague or ambiguous than T`, there is some conclusive evidence against T` which is not conclusive evidence against T. If we discover just this evidence, then we should abandon T`, but we should not necessarily abandon T. I imagine that some would want to say, in this situation, that they had learned that they had chosen the wrong explication. This would be especially tempting if there were another explication t`` of t, such that the theory T``, gotten by replacing every occurrence of t in T with t``, were true, or supported by all of the relevant evidence at hand.

I feel like these senses aren’t strong enough to capture what someone might want to express by saying that explications are open to empirical revision. An explication is empirically revised in this stronger sense not only if the theories in which it occurs are found to be false, and not only if some competing explication better preserves the truth of theories in which the explicandum occurs. But is there such a sense in which explications are open to empirical revision?

Perhaps the idea is that there is some source of empirical evidence that can tell for or against the decision to explicate a term a certain way that is not empirical evidence for or against any particular theory in which the explicatum is used. This seems unlikely to me. What form could this sort of evidence possibly take? If we choose an explication, say, to render the empirical consequences of a theory more transparent, then we might have evidence that the explication fails or succeeds in doing so. We might have evidence, for instance, that “…t`…” is a borderline case but “…t…” isn’t. But would this be empirical evidence? Can’t we tell borderline cases from the armchair, given enough background information? Note that we can supply the necessary background information ourselves, using thought experiments. We might be incapable of telling what the empirical consequences of some explicated or unexplicated theory are if we don’t know what the theory says. So we should be familiar with theories in which explicanda occur in order to make our explications work best. But is this really empirical knowledge, in the relevant sense? What is necessary is not knowledge that any given theory is true, or knowledge of the evidence for or against a theory, but knowledge of what the theory says. (Of course, what makes what one theory says more or less important than what another theory says is the relative likelihood of the truth of the theories, but philosophers qua explicators don’t generally take on the task of empirically assessing the relative likelihoods of theories – generally, I suppose, they assess the importance of a scientific theory on the basis of its prominence in modern scientific discussion.)

Perhaps the idea is that, since no one sentence in which a (non-observational) term occurs is immune to empirical revision, then no sentence we pick out as the explication of a term is immune to empirical revision. This also seems implausible to me. As I understand it, part of what it is to explicate t with t` is to treat “t = t`” (perhaps relative to a given theory) as if it were the definition of t (in that theory). Part of what that amounts to is agreeing to the eliminability of t for t` in all extensional contexts (in a given theory). When we cease to agree to this, we change the subject. In general, as I see it, the explicit adoption of an explication of a term in a theory is an attempt to escape the consequences of various sorts of holism about that theory. We explicate, in part, to make the meanings of terms less diffuse. Of course, if a popular theory containing t is rendered trivially but empirically false by replacing all occurrences of t with t`, then t` is useless as an explication of t in that theory. Nobody would agree to explicate t with t` in such a case, and everyone’s refusal to adopt the explication would be on empirical grounds.

As it stands, this satisfies me that explications are open to empirical revision only in our first two senses. Am I missing something?