from relative confirmation to real confirmation

From Relative Confirmation to Real ConfirmationAuthor(s): Aron EdidinSource: Philosophy of Science, Vol. 55, No. 2 (Jun., 1988), pp. 265-271Published by: The University of Chicago Press on behalf of the Philosophy of Science AssociationStable URL: http://www.jstor.org/stable/187963 .

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DISCUSSION:

FROM RELATIVE CONFIRMATION TO REAL CONFIRMATION*

ARON EDIDIN

Department of Philosophy University of Notre Dame

Recent work on the logical theory of confirmation has centered on accounts of the confirmation of hypotheses relative to auxiliary assumptions or back- ground theory. Whether such relative confirmation actually increases the credibility of the (relatively) confirmed hypothesis will depend in various ways on the epistemic status of the auxiliaries involved. Most obviously, if the auxiliaries are not themselves credible, confirmation relative to them will not increase the credibility of the hypothesis thus confirmed. A complete theory of confirmation must thus combine an account of relative confirmation with an account of the route from relative confirmation to real confirmation. Some recent criticisms of hypothetico-deductive and bootstrapping accounts of relative confirmation are undermined by failure to appreciate the limitations of relative confirmation.

The fundamental question of confirmation theory might be put this way: under what conditions is a theoretical hypothesis confirmed by a piece of evidence? When and to what extent does putative evidence contribute to the credibility of a hypothesis?' The aim of much of modern confirmation theory has been to answer this question in terms of logical relations between hypothesis and evidence. But if we take this as our task, it turns out that we must expand the relations in question to include relata other than hypothesis and evidence alone. To take the simplest and most-dis- cussed example, it turns out that individual hypotheses that are tested experimentally almost never by themselves entail particular experimental outcomes. It is only if we conjoin auxiliary hypotheses to the one we wish to evaluate that testable predictions are entailed (see, for example, Hempel 1966). What in the first instance we're looking for, then, is a logical relation of confirmation of hypotheses by evidence relative to auxiliary assumptions. We must divide the fundamental question of confirmation theory in two:

*Received July 1986. 'Whether and to what extent a piece of evidence contributes to the credibility of a hy-

pothesis will of course vary from inquirer to inquirer (it will depend at least on whether the inquirer knows of the evidence: for those who do not there will be no contribution at all). In what follows I assume the requisite relativity to a given inquirer.

Philosophy of Science, 55 (1988) pp. 265-271. Copyright ? 1988 by the Philosophy of Science Association.

265



266 ARON EDIDIN

(1) When does a piece of evidence confirm a hypothesis relative to a set of auxiliary assumptions?

and

(2) When does such relative confirmation genuinely contribute to the credibility of the hypothesis?

The second question arises because a hypothesis may gain no credibility in spite of strong confirmation relative to certain auxiliary assumptions. This will typically be the case when the auxiliaries are not themselves credible.2 This suggests that an answer to (2) will have to address the epistemic status of the auxiliaries. And this significantly expands the scope of the epistemic input into the confirmation process. We may no longer think of confirmation as a simple matter of transferring epistemic value from observed evidence to posited hypothesis.

Since the auxiliary assumptions will themselves often be theoretical hypotheses, one problem to be faced in answering question (2) is to avoid circularity; it won't do, for example, to say that a hypothesis is genuinely confirmed if it is confirmed relative to other well-confirmed hypotheses! What seems to be needed is some sort of holistic account of the confirmation of entire systems of hypotheses, perhaps in terms of their confirmation relative to one another. That such holism must enter the account of confirmation at some stage will come as no surprise in light of the last century or so of work in the philosophy of science, but it significantly complicates the task of accounting for the confirmation of hypotheses in terms of logical relations alone.

On the other hand, the need for a holistic answer to question (2) does not complicate the task of answering (1). Recent work in logical confirmation theory3 has focused on this question. Good reasons for such a focus are not hard to find. Question (2) as stated presupposes arn account of relative confirmation. In addition, one might hope that the epistemic status of auxiliaries that must be invoked in answering (2) may itself be accounted for in terms of relative confirmation. But an account of relative confirmation cannot by itself determine the conditions under which a hypothesis is genuinely confirmed. This limitation, though it restricts the interest of accounts of relative confirmation alone, also serves to shield such accounts from certain potential counterexamples. You can't refute an answer to (1) by showing that it allows the relative confirmation of a

2Indeed, it seems likely that if (1) is answered in terms of logical relations, then any hypothesis will be confirmed by any observation relative to some assumptions.

3I have in mind especially Glymour (1980a) and responses to the account developed and defended therein. For the latter, see especially Christensen (1983) and the articles in Ear- man (1983).



FROM RELATIVE CONFIRMATION TO REAL CONFIRMATION 267

hypothesis in circumstances in which the hypothesis in fact gains no credibility. It may be that what obstructs genuine confirmation is not the ab- sence of confirmation relative to the assumptions in question, but rather some inadequacy in the status of the assumptions themselves.

Failure to respect the limitations of relative confirmation has led to premature demands for the rejection of two prominent accounts of modes of relative confirmation.4 Both Glymour's criticism of the hypothetico- deductive account of confirmation (Glymour 1980a, pp. 29-48, and 1980b) and Christensen's of Glymour's own bootstrap theory (Christensen 1983) suffer from this fault. Glymour advances many objections to the H-D account, but his most serious criticism seems to be that

The hypothetico-deductive account of confirmation yields . . . the following absurdity. Given a true evidence sentence e, almost any sentence S is confirmed by e with respect to some true theory. More precisely, let e be a true not logically valid sentence and S any sentence at all that is both consistent and not a logical consequence of -e; then S is confirmed by e with respect to (S -> e), which is true. (Glymour 1980a, p. 36)

Why is this an absurdity? Certainly absurd cases of such relative confirmation come easily to mind. The fact that salt dissolves in water (e) confirms the hypothesis that the moon is made of green cheese (S) relative to the true claim that if the moon is made of green cheese then salt dissolves in water (S -> e). According to the H-D account, this is a case in which an observed fact confirms a hypothesis relative to an auxiliary as- sumption which we know to be true. But I hope it doesn't make you any more confident that the moon is made of green cheese. Does this show that the proposed account of relative confirmation is incorrect?

An alternative diagnosis is that we have a genuine case of relative confirmation that is not a case of confirmation simpliciter. Support for this second diagnosis may be found by considering other cases that share the formal structure of the absurd one. Suppose that we have good reason to believe S -* e and that this evidence is independent of (and perhaps available prior to) our evidence concerning e. Here the discovery that e is true will add to the credibility of S. This seems to be just the sort of gener- alized testing of hypotheses by their consequences for which the H-D account of relative confirmation is designed. (It would not be misleading to say that we care about credible hypotheses whose conjunction with S entails e because they give us reason to believe S -> e. This is another

4In what follows, what I call "accounts of relative confirmation" should be understood as accounts of particular modes of such confirmation. In this sense, different accounts of relative confirmation need not be rivals. They may instead simply describe different ways in which hypotheses may be confirmed relative to auxiliary assumptions.



268 ARON EDIDIN

way of saying that the function of auxiliary hypotheses is to connect the hypothesis at issue to the evidence.) But to complete the account of this sort of testing and confirmation more is required. We need to know what status S -> e must enjoy for confirmation relative to it to yield confirmation simpliciter. We knew before considering Glymour's "absurdity" that auxiliaries involved in genuine confirmation must themselves be credible. It now appears that their credibility must be substantially independent of the credibility of the evidence involved in the confirmation.5 The appropriateness of this requirement emerges if we consider the ra- tionale for testing hypotheses via their consequences. We want evidence that things are as the hypothesis (perhaps in conjunction with auxiliary information) entails that they must be. If the auxiliary "information" is credible only because of the evidence in question, then in effect the evidence is itself among the collateral information necessary (for us, in the given epistemic situation) to connect the hypothesis to the evidence. But if the collateral information itself entails the evidence (and, a fortiori, if it includes the evidence), then the fact that its conjunction with the hypothesis entails the evidence does nothing to reveal otherwise hidden con- nections between hypothesis and evidence. The point can be made even more clearly if we consider the testing aspect of confirmation. Checking the consequences of a hypothesis tests the hypothesis because their failure entails its falsehood. Checking the consequences of a hypothesis con- joined with auxiliary information can test the hypothesis to the extent that the failure of the consequences would disconfirm the hypothesis. But if the only reason we have for believing the auxiliaries is that we already believe the consequence in question, then the discovery that the consequence is false need cast no doubt on the hypothesis at all, since such a discovery would disconfirm the auxiliaries. So it seems to be a condition of unqualified hypothetico-deductive confirmation that the auxiliaries involved be credible independently of the evidence invoked. That this condition of unqualified confirmation may be violated in cases that satisfy the conditions of the H-D account of relative confirmation need cast no doubt on the soundness of the latter.

In his role as critic of H-D accounts of relative confirmation, Glymour is guilty of failing to appreciate the significance of the gap between confirmation relative to auxiliaries and confirmation simpliciter. In his role as proponent of his "bootstrapping" account of relative confirmation, he is the victim of a similar failure on the part of at least some of his critics.

5Not entirely independent, since, for example, even if S -> e is independently credible the discovery that e is true would generally make it still more credible, and the discovery that e is false would make it somewhat less so.




Christensen, for example, notes that if T is a theory equivalent to the conjunction of

H1: (x)(Rx-> Bx)

and

H2: (x)Gx

then on Glymour' s account

E: Ra & Ba

confirms H2 relative to T. The reason is that there are members of T whose conjunction with E entails an instance of H2. An example of such an auxiliary is

Aux: (x) [(Rx-* Bx) *-> Gx].

But, writes Christensen, "one would not want E to confirm H2. (Take H1 to be the famous 'Raven hypothesis', and H2 to be the pantheistic hypothesis.)" (Christensen, 1983, p. 473) 6 Surely we don't want the discovery of another black raven to confirm the hypothesis that everything is divine! On the other hand, the bootstrap theory doesn't tell us that E actually lends any credibility to H2 in the case described. All that follows from Glymour's account is that E confirms H2 relative to T. Christensen seems to have in mind a situation in which we have no reason to believe Aux that is independent of whatever antecedent reason we have to believe H2. (This is certainly true of the raven/pantheism case.) In such a case, E certainly does fail to confirm H2. But the reason for the failure clearly concerns the epistemic status of Aux rather than any problem with the relative confirmation of H2. As before, it's easy to see what goes wrong. The auxiliaries involved in an instance of bootstrap confirmation are what connect the evidence to the hypothesis. If the auxiliaries have no antecedent credibility independent of that of the hypothesis, then we will find the evidence relevant to the hypothesis only if we antecedently assume that the hypothesis is true. But "confirmation" that requires antecedent commitment to the truth of the hypothesis in question is clearly no confirmation at all.

Again, support for this diagnosis of the case at hand gains support if we consider formally parallel cases that differ from it with respect to the

6Christensen's other alleged counterexamples are similar to this one in the relevant re- spects, and so require no separate discussion. The entire battery of examples is conve- niently laid out in Glymour (1983). Glymour, to my mind incorrectly, accepts Christen- sen's counterexamples as genuine and modifies his account to avoid attributing relative confirmation in the cases in question.



270 ARON EDIDIN

epistemic status of the auxiliaries. Suppose that we have reasons to believe Aux that are independent of both our evidence for E and our antecedent evidence for H2. For example, let H1 be the hypothesis that all minds are embodied and let H2 be the materialist hypothesis. Then Aux will be equivalent to the claim that all and only disembodied minds are immaterial objects. If we have independent reason to believe this, then discoveries of embodied minds will tend to confirm the materialist hypothesis. The discovery that E is true will lend credibility to H2 by con- firming one of its instances; in this case, (Ra & Ba) truly confirms Ga and thus (x)Gx.

Neither Glymour's purported counterexample to the H-D account of relative confirmation nor Christensen's to Glymour's own bootstrapping account succeeds in discrediting its target. The reason is the same in both cases: failures of confirmation need not be failures of relative confirmation. In each instance, it seems clear that any adequate account of how relative confirmation yields confirmation simpliciter will rule out the undesirable cases even if they are genuine cases of relative confirmation.7

It doesn't follow, of course, that the cases described by Glymour and Christensen are genuine cases of relative confirmation. The latter claim gains some support from the fact that it seems possible to transform them into cases of genuine (unqualified) confirmation by altering the epistemic status of the auxiliaries involved. But such considerations are not deci- sive. It may be that the best approach to relative confirmation will exclude the undesirable cases and explain the apparently related cases of genuine confirmation in some other way. For example, apparently successful con- firmations of S by e relative to the material conditional S -> e might really be cases of confirmation relative to some stronger conditional which, unlike its material counterpart, is not true in the "absurd" cases. To evaluate such a claim, of course, one would need to see the details of the com- peting account of relative confirmation. Ideally, one would also want to see how the rival accounts of relative confirmation meshed with appro- priate accounts of the route from relative to unqualified confirmation. What all this reflects is the fact that accounts of (kinds of) relative confirmation must ultimately be evaluated in the context of overall accounts of confirmation which must themselves in the final analysis be evaluated as wholes. But even without a comprehensive account in which to locate them, both the H-D and the bootstrapping accounts of relative confir-

7In Edidin (1981, 1983) I offer counterexamples to the version of bootstrapping advanced in Glymour (1980a). My discussion in those articles shares the fault that I here attribute to Glymour and Christensen. I think, though, that the counterexamples themselves, unlike Glymour's and Christensen's, do not depend on the epistemic status of the auxiliaries invoked. I am therefore inclined to think that my counterexamples cannot be dealt with in the way that I propose for the others.




mation exhibit striking virtues. Each offers a straightforward and pow- erful account of relative confirmation that contributes, in combination with plausible conditions on the epistemic status of auxiliaries, to intu- itively satisfying explanations of various cases of confirmation or its ab- sence. And this in turn suggests that these two kinds of relative confirmation provide us with a promising basis for further exploration of the conditions of genuine, unqualified confirmation.

REFERENCES

Christensen, D. (1983), "Glymour on Evidential Relevance", Philosophy of Science 50: 471-481.

Earman, J. (ed.) (1983), Testing Scientific Theories: Minnesota Studies in the Philosophy of Science, Vol. X. Minneapolis: University of Minnesota Press.

Edidin, A. (1981), "Glymour on Confirmation", Philosophy of Science 48: 292-307. . (1983), "Bootstrapping Without Bootstraps", in Earman (1983), pp. 43-54.

Glymour, C. (1980a), Theory and Evidence. Princeton: Princeton University Press. . (1980b), "Hypothetico-Deductivism is Hopeless", Philosophy of Science 47: 322-

325. . (1983), "Discussion: Revisions of Bootstrap Testing", Philosophy of Science 50:

626-629. Hempel, C. (1966), Philosophy of Natural Science. Englewood Cliffs, N.J.: Prentice-Hall.



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