of theories
NMA has been preceded by quite similar statements by J. J. C. Smart (1963) and Grover Maxwell (1970). In Smart and Maxwell’s approaches, the archrival of realism is the instrumentalist understanding of science.
Semantic instrumentalism assumes that the language of science is to be divided into an observational and a theoretical part. The observational lan-guage contains, apart from the logical vocabulary, only observational terms, directly connected to the empirical world through ‘operational definitions’. As pointed out in the introductory chapter, non-eliminative semantic instrumen-talism takes theoretical terms to have the role of systematizing observational statements, thus making theories more simple and economical. They are lin-guistic instruments which have no referents, so that the statements containing them do not have truth values. Thus, according to instrumentalism, state-ments about, say, electrons are nothing but instrustate-ments meant to enable us to make predictions at observational level of tracks in the cloud chamber.2
For reasons of convenience, instrumentalism is sometimes depicted in terms of a ‘black box’ metaphor. In the suitable description by Bird,
One puts into the box information regarding observed background condi-tions, and the box generates predictions regarding what one will observe.
What one wants from such a black box is that if the input information is accurate, then the predictions it yields will be accurate too. We are not especially concerned with the mechanism inside the box. That can be anything so long as it works. In particular, there is no requirement that it depict the way the world is. (Bird 1999: 125–6)
Smart argued that instrumentalism has no means to account for a multitude of ontologically disconnected phenomena other than belief in cosmic coinci-dences. By contrast, scientific realism offers a close-at-hand and reasonable explanation, which leaves no room for large scale fortuitousness. As Smart puts it,
Is it not odd that the phenomena of the world should be such as to make a purely instrumental theory true? On the other hand, if we interpret a theory in the realist way, then we have no need for such a cosmic coincidence: it is not surprising that galvanometers and cloud chambers behave in the sort of way they do, for if there are really electrons, etc., this is just what we should expect. (Smart 1963: 39)
2I shall henceforth be explicit about the varieties of instrumentalism whenever the dis-tinction is relevant, and the context itself cannot indicate it.
At a first sight, Putnam’s and Smart’s formulations are virtually identical: the first speaks of miracles, while the latter speaks of cosmic coincidences. How-ever, as Psillos (1999: 72–3) has pointed out, their argumentative structures are different. While Putnam’s argument is empirical, Smart’s one is a conceptual analysis; i.e., while Putnam’s NMA relies on an abductive inference, Smart’s argument is part of his attempt to clarify a conceptual dispute concerning the ontological foundations of science. The realist–instrumentalist dispute in-stantiates such conceptual confrontation with respect to the interpretation of scientific theories. As Psillos properly states,
...Smart’s ‘no cosmic coincidence argument’ relies on primarily intuitive judgements as to what is plausible and what requires explanation. It claims that it is intuitively more plausible to accept realism over instru-mentalism because realism leaves less things unexplained and coincidental than does instrumentalism. Its argumentative force, if any, is that anyone with an open mind and good sense could and would find the conclusion of the argument intuitively plausible, persuasive and rational to accept – though not logically compelling. (Psillos 1999: 73)
So Smart argued from the intuitive plausibility of the realist position. His
‘no cosmic coincidence’ argument relies on intuitive judgements about what is plausible and what needs to be explained. The point, as Psillos phrases it, is that it’s intuitively more plausible to accept realism over instrumentalism because realism leaves less things unexplained and coincidental than realism does (cf. Psillos 1999: 73).3
An attempt to account for the plausibility of the realist judgements was made by Maxwell (1970), who turned to the epistemic virtues – such as ex-planatory power, simplicity, comprehensiveness, lack of ad hocness – of realis-tically interpreted scientific theories:
As our theoretical knowledge increases in scope and power, the competi-tors of realism become more and more convoluted andad hoc and explain
3We should note that many realists are wary of talk of conceptual analysis and a priori reasoning. The so-calledepistemological naturalists (see BonJour (1998) defend the thesis that the one and only way for knowledge acquisition is empirical. Devitt’s (1997, 1998) motivation for this position is, first, that the very idea of the a priori is obscure and second, that it is unnecessary, since an empirical approach of justification seems to be available.
Stich (1998) argues that all that can be obtained by analysis knowledge about our implicit assumptions about the nature of things – assumptions embedded in our language – and no knowledge about the nature of things themselves. However, without trying to resolve here this complex debate, I agree with Jackson’s (1998) that “there is a lot of ‘closet’ conceptual analysis going on” (1998: vii). For example, one’s utterance that sentence ‘Jones is six foot and Smith is five foot ten’, implies that Jones is taller than Smith (cf. Jackson (1998: 3)). It is precisely in this sense that an analysis of sentences’ semantic properties can be located in an empirical account of the world: semantic is actually being entailed by naturalism.
less than realism. For one thing, they do not explain why the theories they maintain are mere cognitively meaningless instruments are so successful, how it is that they can make such powerful, successful predictions. Re-alism explains this very simply by pointing out that the predictions are consequences of the true (or close true) proposition that comprise the theories. (Maxwell 1970: 12)
Maxwell obviously submits that statements displaying epistemic virtues are more plausible than those which lack such virtues. Thus, as Psillos (1999: 74–5) indicates, Maxwell gives a Bayesian twist to his argument. Supposing that both realism and instrumentalism entail the empirical success of scientific theories, they will both have likelihoods equal to unity:
p(S |R) =p(S |I) = 1,
whereR stays for realism, I for instrumentalism, andS for the empirical suc-cess of scientific theories. According to Bayes’s theorem, the posterior proba-bilities of realism and respectively, instrumentalism, are
p(R|S) =p(R)/p(S) p(I |S) =p(I)/p(S),
where p(R) is the prior probability of realism, p(I) is the prior probability of instrumentalism, and p(S) is the probability of science’s success. Certainly, p(S) does not depend on the philosophy of science which accounts for it, so that it has the same value for both realism and instrumentalism. Therefore,
p(R|S)
p(I |S) = p(R) p(I)
That means that any difference in the degree of confirmation of realism and instrumentalism stems from a difference in their respective priors.4 Arguing that realism is clearly better supplied with epistemic virtues than realism – an idea that many antirealists will, of course, not accept5 – Maxwell infers that the prior probability of realism is much higher than the prior probability of instrumentalism.
4The reference to prior probabilities underlines the difference from Putnam’s NMA, as Wolfgang Spohn (personal correspondence) points out.
5This line of argument goes exactly opposite to the more popular Popper/van Fraassen inference from the fact that the probability of the observational consequences of any theory is at least equal or higher than the probability of the theory itself, to the conclusion that instrumentalism is generally more probable than realism. I shall have more to say about this in chapter 7, where I shall reject this latter line of argument.
It will be seen that, in spite of their merits in undermining the credibility of
‘black box’ instrumentalism, Smart’s and Maxwell’s arguments are vulnerable when faced with more sophisticated versions of instrumentalism, such as van Fraassen’s constructive empiricism.