The incoherence arguments

There is a second argument addressing van Fraassen’s phenomenology of sci-ence, which aims to show that it is incoherent. Paul Horwich (1991) argues that there is no ascertainable difference between believing and accepting a theory.

Hence, there is no difference in the doxastic attitudes presumed to correspond to the observable and, respectively, the unobservable realms.⁴

Recall that acceptance of a theory consists in believing only its observable consequences. Horwich sets out to show that we could not accept a theory without also believing it. His starting point is the suggestion that any attempt

3Things become more complicated when those supposed to carry out such a study are themselves split-minded.

4Our account reflects the influence of Kukla’s (1998: 106–10) persuasive analysis of Hor-wich’s argument.

to formulate a psychological theory of beliefs would lead us to defining beliefs in terms in which instrumentalists describe acceptance:

If we tried to formulate a psychological theory of the nature of belief, it would be plausible to treat beliefs as states with a particular kind of causal role. This would consist in such features as generating predictions, promoting certain utterances, being caused by certain observations, en-tering in characteristic ways into referential relations, playing a certain part in deliberation, and so on. But this is to define belief exactly in the way instrumentalists characterize acceptance. (Horwich 1991: 3)

Horwich considers this aprima faciecase for identifying belief with acceptance.

He then argues against four possible considerations that could be called on to support the distinction of belief from acceptance:

(i) the idea that true believers believe that they believe, while those who merely accept do not;

(ii) the observation that even realists sometimes use a theory for practical purposes without believing it;

(iii) the idea that, unlike instrumentalism, realism is committed to a corre-spondence theory of truth;

(iv) the appearance that an increase in the usefulness of a theory leads to a decrease in its believability.

We shall consider only sketchily the first three points, and enter into the details of the fourth one, because the failure of Horwich’s argument is related to it – or so will be argued. (i) cannot be a serious basis for distinguishing between belief and acceptance, since one’s psychological states need not reflect straightforwardly one’s epistemic attitudes. That is, one can be confused or mistaken about one’s beliefs to the effect of denying those beliefs, even when holding them. (ii) is also an insufficient basis for the distinction, since local uses of instrumentalism by no means preclude an overarching realist approach (see our discussion of selective realism in chapters 2 and 7). (iii) is no threat at all to Horwich’s thesis, for scientific realism is not committed to a correspondence theory of truth (see the introductory chapter).

As far as (iv) is concerned, it summarizes an argument by van Fraassen (1985). He suggests that theoretical unification results in a theory ofincreased acceptability – simpler and pragmatically more useful – but alsodecreased be-lievability– because additional claims make it more likely to go wrong. Hence,

“belief and acceptance should respond differently to theoretical unification, and so cannot be the same thing.” (Horwich 1991: 7).

Horwich’s criticism against van Fraassen’s argument is that it fails to spec-ify any property that applies to belief but not to acceptance, or conversely.

Both beliefs and acceptance, Horwich maintains, are to be evaluated from a double standpoint: epistemic andpragmatic. Epistemic evaluation takes place in relation to the available evidence, according to epistemic norms. Pragmatic evaluation takes place in relation to practical consequences, according to prag-matic values. It is in the latter sense that Pascal recommends us to believe in God. In these terms, van Fraassen’s argument is that theoretical unification urges us, from an epistemic viewpoint, to decrease the credibility of the total theory and, from a pragmatic viewpoint, to increase the acceptability of the to-tal theory. There appears thus a tension between the epistemic imperative and the practical one. But this is precisely the point contended by Horwich. He argues that belief and acceptance co-vary under the epistemic and pragmatic dictates. Practical reason commends that we increase our credence in the uni-fied theory, and epistemic reason commends that we increase the acceptability of the unified theory. Therefore, “belief and acceptance will respond in the same way to theoretical unification.” (Horwich 1991: 7).

Unlike Horwich, van Fraassen seems to deny that pragmatic rationality is involved in the assessment of beliefs. That would imply that, after all, accep-tance and belief respond differently to pragmatic considerations. Yet, as Kukla (1998: 107–8) convincingly argues, the point of dispute is only terminological.

If we are capable of both epistemic and pragmatic evaluations, we should be capable to undertake them either separately or jointly, at our convenience. If, on the one hand, belief can be evaluated exclusively in epistemic terms, van Fraassen can hold his point. If, on the other hand, pragmatic considerations are also needed in evaluating beliefs, then all that constructive empiricists need is a reformulation of their notion of ‘belief’ limited to epistemic considerations.

As Kukla suggests, a notion of epistemic belief – which is just belief purged from its pragmatic component – is everything that van Fraassen requires to save the coherence of his distinction:

There can be no doubt that we’re capable of epistemic belief, since the cognitive resources needed for epistemic-believing are a proper subset of those needed for forming and evaluating garden-variety beliefs. Nor can there be any doubt that epistemic belief is different from acceptance, for the latter is affected by pragmatic considerations whereas the former is not. But the distinction between epistemic belief and acceptance is enough to formulate the constructive empiricist viewpoint in a coherent manner: constructive empiricists maintain that there may be good rea-sons for accepting scientific theories, but never for epistemic-believing more than their empirical consequences. (Kukla 1998: 107–8)

In his argument, Horwich claims that the difference between epistemic and

pragmatic beliefs does not correspond to any ascertainable difference between states of mind. He expects constructive empiricism to be able to indicate a behavioral difference resulting from believing and, respectively, accepting a theory. However, in line with Kukla (1998: 109), I don’t see that the identity of behavioral dispositions must correspond to the identity of mental states.

Believing a theory and accepting it may well be different mental states, even if their corresponding behavioral dispositions are the same. One may follow, for instance, the prescriptions of a religious doctrine either from innermost piety, or as in Pascal’s wager, from cunning calculation. Even if God almighty will know the difference, we, who rely on one’s behavioral dispositions, may never be able to identify one’s real credence. Similarly, one can believe a theory for epistemic reasons, or merely accept it pragmatically. In both eventualities, there may be no hint as to what is actually going on in that scientist’s mind.

As argued in 2.3, the constructive empiricist has difficulties in justifying her cognitive state. In particular, I do not believe that she is able to explain where the pragmatic benefits of a theory – on which its acceptance relies – come from. But this is quite a remote issue, with no relevance to the coherence of the constructive empiricist distinction between belief and acceptance.

Consequently, Horwich’s argument that the coherence of constructive em-piricism depends on whether belief and acceptance are different mental states, fails to reach its purpose. The inability to establish differences in the be-havioral dispositions of believers and accepters does not entail that they are, respectively, in identical cognitive states. All that Horwich’s argument shows is that van Fraassen may have a terminological problem when using ‘belief’ in a strictly epistemic sense, i.e. deplete of its pragmatic side. But this can easily be explained away, so that constructive empiricism remains unscathed.

Musgrave’s argument

Alan Musgrave (1985) brings forth another argument purporting to reveal the incoherence of van Fraassen’ distinction between belief and acceptance.

Suppose we have scientific means to tell that the class A of phenomena is observable by humans, whereas the classB is not. Assume that we use the-oryT, the “final physics and biology.” Now, constructive empiricists acceptT solely as empirically adequate – true as to its observable statements. But what should we do with a sentence like “B is not observable by humans”? On pain of contradiction, the statement cannot be about observables. If it is not about observables, then it can only be accepted, not believed. In fact, Musgrave maintains, there is nothing that constructive empiricists can consistently say about unobservables: “anyone who claims to have observed something about unobservables contradicts himself.” (1985: 207). Therefore, as Musgrave

con-cludes, constructive empiricism seems to be founded on a spurious distinction.

Van Fraassen has a smart answer to this objection:

Musgrave says that “B is not observable” is not a statement about what is observable by humans. Hence, if a theory entails it, and I believe the theory to be empirically adequate, it does not follow that I believe that B is not observable. The problem may only lie in the way I some-times give rough and intuitive rephrasings of the concept of empirical adequacy. Suppose T entails that statement. ThenT has no model in which B occurs among the empirical substructures. Hence, ifB is real and observable, not all the phenomena fit into a model ofT in the right way, and then T is not empirically adequate. So, if I believe T to be empirically adequate, then I also believe that B is unobservable if it is real. I think that is enough. (van Fraassen 1985: 256)

In other words, if T is empirically adequate, Musgrave’s argument demon-strates that constructive empiricists must believe that the class B of phenom-ena either does not exist, or it is unobservable. This is logically equivalent to saying that if B exists, then it is unobservable. Surely constructive empiri-cists can consistently claim that B is unobservable, provided that B exists.

If so, that means that they can entertain beliefs about entities whose exis-tence is forever beyond our ken, if those entities exist. In other words, the constructive empiricist cannot believe in unobservable entities, but she has no trouble in believing in unobservables-if-they-exist. There is, strictly speaking, no incoherence in the sense pointed out by Musgrave.

However, there is an important price that constructive empiricism must pay for this manoeuver. The constructive empiricist is not allowed to believe in unobservables unless they exist – all right so far. But she must also be justified in this belief, meaning, she ought toknow about those unobservable’s existence. This urges either a God’s eye view, or the employment of some ampliative procedure. However, both these epistemic steps are precluded by the empiricist doctrine of relying solely on sense experience. Accordingly, T – the theory entailing that “B is not observable” – cannot be known to be empirically adequate by employing procedures relying solely on observation.

Therefore, though indirectly, Musgrave’s argument inflicts a severe injury to constructive empiricism.

Friedman’s argument

The last incoherence argument to be considered belongs to Michael Friedman (1982). This argument, which I take to be fatal to constructive empiricism, turns out to be fairly simple. It was presented by Friedman in a short book review on van Fraassen’s The Scientific Image.

Friedman objects that van Fraassen is telling us, on the one hand, that we can only believe in the observational consequences of our successful theories and, on the other hand, that those consequences can only be expressed in a theory-laden language. Here is how Friedman puts it:

Suppose that I, speaking the language of contemporary physics, assert the empirical adequacy of that theory: viz.

The observable objects are embeddable in the world picture of modern physics.

(i.e., the observable objects behaveas if they were a subpart of the world of physics). But “the observable objects” are themselves characterized from within the world picture of modern physics: as those complicated systems of elementary particles of the right size and “configuration” for reflecting light in the visible spectrum, for example. Hence, if I assert that observable objects exist, I have also asserted that certain complicated systems of elementary particles exist. But I have thereby asserted that (individual) elementary particles exist as well! I have not, in accordance with van Fraassen’s “constructive empiricism”, remained agnostic about the unobservable part of the world. (Friedman 1982: 278)

In different words, the problem is that if, following constructive empiricism, one believes the observable consequences of a theoryT, and if T has the existence of entity X as an observable consequence, it follows that one must believe in the existence ofX. Suppose for instance, that it is a consequence of quantum theory (in conjunction with many other convenient auxiliary assumptions) that the table in front of me is a structure composed of more than 10²⁵ atoms.

Consequently, since I believe quantum theory to be empirically adequate, I believe in the existence of this particular structure of 10²⁵ atoms meaning, I believe that a structure of 10²⁵ atoms exists. So, the belief logically follows that atoms exist. Hence, by following constructive empiricism, I have logically come to believe in the existence of unobservable entities, thus contradicting constructive empiricism. Therefore, constructive empiricism is incoherent.

There are two elements whose conflict results in this poser: the fact that van Fraassen resolutely admits the theory-ladenness of any scientific description, while also taking the language of contemporary physics to be the ultimate lan-guage for describing the empirical world. As we have seen, van Fraassen takes observation to mean detection by the unaided senses. Yet, he maintains that we cannot describea priori the limits of observability. Science itself should tell what is observable and what not. This implies that every observation report is theory-contaminated, so that it cannot serve as a theory-neutral platform.

Van Fraassen is aware that there is a circularity here, but he maintains that it’s not of a vicious kind. He calls it thehermeneutic circle:

To delineate what is observable ... we must look to science ... for that is an empirical question. This might produce a vicious circle if what is observable were itself not simply a fact disclosed by theory, but rather theory-relative or theory-dependent. It will already be quite clear that I deny this; I regard what is observable as a theory-independent question.

It is a function of facts about us qua organisms in the world, and these facts may include facts about the psychological states that involve con-templation of theories – but there is not the sort of theory-dependence that could cause a logical catastrophe here. (van Fraassen 1980: 57–8)

Van Fraassen suggests that human beings’ minds and organisms are to be understood as a part of nature. They ought to be discovered in nature rather than helping to establish nature. This is why the fact that natural events are described within the conceptual framework of modern science should not wipe out the distinction between what is observable and what not. As he puts it,

Everything in the world has a proper classification within the conceptual framework of modern science. And it is this conceptual framework which we bring to bear when we describe any event, including an observation.

This does not obliterate the distinction between what is observable and what is not – for that is an empirical distinction – and it doesnot mean that a theory could not be right about the observable without being right about everything. (van Fraassen 1980: 58)

Indeed, the point is not that the distinction between observable and unob-servable is obliterated. We are not claiming that van Fraassen’s “hermeneutic circle” is vicious. There are clear cases and counter-cases of observability, and a serviceable concept of the observable can be achieved. It may also be admit-ted that what is observable is (up to some psychological details to be discussed in the next section) a theory-independent issue.

However, the problem is that scientific theories accepted as empirically adequate entail observable consequences. These consequences are, on the one hand, to be believed, and on the other hand, fully theory-dependent. If we have reason to disbelieve such a theory, then we implicitly have reason to disbelieve what it says it is observable. Van Fraassen correctly points out that a “theory could be right about the observable without being right about everything”.

Nonetheless, if we refuse to believe in (or are agnostic about) that theory, then this is a strong reason for us to refuse to believe in (or be agnostic about) what it says that it is observable. In order to escape Friedman’s problem, van Fraassen needs a theory-neutral concept of observation. However, since he himself tells us that there is no theory-neutral language, we can only conclude that constructive empiricism is indeed incoherent.

A tentative way out for constructive empiricism was put forth by Newton-Smith. He suggested that if we placed ourselves into van Fraassen’s perspec-tive, we have to admit current scientific theories are juststories:

...stories to which it may be pragmatically useful to adhere – but stories for which there are underdetermined rivals (albeit unknown to us at this time). Observable objects are embedded in the world-picture of modern science. On that picture these observable objects have such-and-such con-stituents of elementary particles. But . . . there is another picture which give these observable objects quite different constituents. So given this plurality of pictures and no rational reason to select one picture from the others, best to regard the “world picture of modern physics” as just one fairy tale among other and not to believe it. (Newton-Smith 2000, personal correspondence)

I agree with Newton-Smith that this position would circumvent Friedman’s problem. But this is rather a species of non-eliminative instrumentalism, and not van Fraassen’s position. Van Fraassen is strongly committed – in the sense of acceptance, not belief – to the epistemically privileged language of modern science. The latter is by no means “one fairy tale among others.” As van Fraassen has emphasized, contemporary physics is the only world picture able to account consistently for the vast corpus of experimental data that we have.

It is precisely this uniqueness of its epistemic commitment that leads construc-tive empiricism to conflict with the theory-ladenness of language. For example, if we had an empirically successful alternative to quantum theory which would imply that the table in front of me is composed of 10⁶ micro-entities-of-a-non-atomic-kind (and not, as we have assumed that quantum theory implies, of 10²⁵atoms), then Friedman’s problem would be blocked by the underdetermi-nation of belief in atoms and, respectively, belief in those micro-entities-of-a-non-atomic-kind, from the same observation. But van Fraassen takes quantum theory at face-value. He unmistakably speaks of atoms as table’s constituents, and not of other logically possible fictions. That engenders a fatal tension. As Friedman puts it,

The point is that one cannot take the language of modern physics to be the one and only language for describing the world and, at the same time,

The point is that one cannot take the language of modern physics to be the one and only language for describing the world and, at the same time,