Scientific realism has been located on the vertical, ontological dimension of realism. It has been defined via the claim that the unobservable entities posited by scientific theories, such as electrons and genes, exist independently of us.
We can acquire a more precise understanding of scientific realism by ana-lyzing it under the ontological, semantic, and epistemic aspects that we have identified within the general doctrine of realism.
Metaphysical scientific realism – henceforth MSR – is the claim that the unobservable entities posited by science exist objectively and independently of us. It assumes the existence of common-sense entities like stones and trees.
We saw that the opponent of the doctrine of realism on the ontological line was the idealist. However, to deny scientific realism does not in the least involve a radical departure from belief in the existence of an independent ex-ternal world. One can dismiss scientific realism while embracing commonsense realism. From the position of commonsense realism, a rejection of MSR will mean either to take all sentences about scientific unobservables as being false;
or to be agnostic about the existence of such entities; or, finally, to take it that all such sentences are ill-formed, hence nonsensical.
Semantic scientific realism – henceforth SSR – is the claim that all state-ments about theoretical entities have truth values. As pointed out above, semantic realism only tells us what the truth-makers of factual sentences are, i.e. how the world should be in order to make these sentences truth-valuable.
This does not involve that the world is indeed like that. Particularized to SSR, the claim is that statements about theoretical entities are truth-valuable. As Kukla indicates, the statement “Electrons are flowing from pointAto pointB”
would be true if and only if electrons were indeed flowing fromAtoB. (Kukla 1998: 8). Yet to accept all of this does not mean that the actual existence of electrons must be accepted, nor anything else about their properties.
The rejection of SSR can well take place from the position of common-sense semantic realism. This is the stance taken insemantic instrumentalism,
through both its variants: eliminative and non-eliminative. Eliminative se-mantic instrumentalism (also known as reductionism) states that theoretical terms are to be defined in observational terms, and that theoretical statements are to be translated into observational statements. Presupposed, of course, is a clear-cut distinction between the theoretical and the observational, an idea which we shall criticize and reject in chapter 4. Non-eliminative semantic instrumentalism views theoretical terms as semantically uninterpreted instru-ments useful for organizing observations.
Epistemic scientific realism – henceforth ESR – is usually taken to be the claim that we can and do acquire knowledge about the existence of theoretical entities.
ESR requires multiple qualifications.
(1) According to the object of knowledge, there are two kinds of ESR: a restrained kind, claiming knowledge only of the existence of theoretical entities, and an extended one, additionally claiming knowledge of the properties of, and relations between, these entities. The former will concern us throughout this work.
(2) According to the strength of the knowledge claims, there is a strong ESR stating that we know our scientific theories to be strictly true. Yet such an infallibilism is so fragile as to be untenable. First,all past scientific theories turned out to be stricto sensu false, so that, by “pessimistic meta-induction”, we can conclude to the very low probability of our current theories being all true. Second, any scientific theory involves idealizations, approximations, and ceteris paribus clauses, which inevitably induce a degree of imprecision in the scientific statements. Therefore, to embrace epistemic standards so high so as to accept only literally true sentences would mean virtually to expel the entire body of science (see the Appendix).
Scientific realists have learned the lesson of fallibilism. They do not actually claim more than knowledge of the approximate truth of our well-established theories. Approximate truth has been criticized for lack of conceptual clarity by both friends and foes. As shown in the Appendix, while some scientific realists, such as Devitt (1991) and Psillos (1999) advocate for an intuitive notion of approximate truth, critics – among which Laudan (1981) is the most adamant – object that the concept lacks the minimal clarity needed in order to ensure whether it can be of any philosophical avail. However, Niiniluoto (1999) offers a robust theory of approximate truth and of its cognates, truthlikeness and verisimilitude. We rely upon it when embracing the claim that we have knowledge of the approximate truth of our best theories.
A weaker epistemic claim is that we are rationally warranted to believe in our well-established theories. This position circumvents the attack by pes-simistic meta-induction, but only at the price of a major inconvenience: it
cannot explain the methodological success of science (see 2.4).
By descending even further down the epistemic scale, we reach the point where is it claimed that “it is logically and nomologically possible to attain a state that warrants belief in a theory.” (Kukla 1998: 11). Such a view can barely explain anything about science. I take it that its only merit is didactic:
it shows how closely one can get to scepticism while still remaining an epistemic realist.
Anything that goes underneath this level ought to be called epistemic an-tirealism. Van Fraassen’s constructive empiricism, which we shall discuss in detail, is a famous species of epistemic antirealism. Van Fraassen believes in the truth of scientific theories with respect to their observable posits, but de-clines belief when it comes to unobservables. Constructive empiricism takes empirical adequacy, and not truth, as the goal of science. Accordingly, em-pirically successful theories are to be accepted, i.e. believed to be empirically adequate, and not believed to be (approximately) true. We shall devote ex-tensive space to criticizing constructive empiricism in several respects – see sections 2.1, 2.4, and 3.2.
After having exposed the varieties of scientific realism and the conceptual relations between them, it is appropriate to present our working definition of scientific realism:
Scientific realism is the doctrine according to which
(i) Most of the essential unobservables posited by our well-established cur-rent scientific theories exist independently of our minds.
(ii) We know our well-established scientific theories to be approximately true.
Claim (i) was stated by Devitt (2003) and presents the ontological aspect of scientific realism. We shall discuss in chapter 6 one important contender of the independence dimension of realism: social constructivism. It will be distinguished between many varieties of social constructivism, which will be inspected from the standpoint of their consistency. Among them, radical social constructivism denies that there is any part of the external world which is not of our making; all facts are the outcomes of collective intentional activity.
Thus, radical constructivism turns out to be a form of idealism.
Claim (ii) underscores the epistemic aspect of our concept of scientific realism. Epistemic scientific realism is seriously challenged by the underdeter-mination argument, which constitutes the themes of chapters 4 and 5. One premise of the underdetermination argument is the empiricist assumption that the only warranted knowledge is that concerning observable entities. The sec-ond premise is that for any given body of observational evidence, there are indefinitely many theories which entail it. Therefore, as the argument goes,
the epistemic ascent to any particular theory is blocked. In other words, the-ories are underdetermined by the empirical data.
In chapter 4, we shall criticize and dismiss the underdetermination argu-ment by showing that there is no principled way to draw a distinction between the observable and the theoretical, on which its first premise relies. We ar-gue next (chapter 5), that even if such a distinction could be made, the second premise (the empirical equivalence thesis) cannot be established in a form that generally blocks epistemic ascent to the best theory.
An implicit point about the definition of scientific realism concerns its scope of application. Scientific realism is often taken as a global, overarch-ing doctrine, appropriate in accountoverarch-ing for most cases of successful scientific practice. However, scientific realism ought to be more true to scientific life:
it ought to do justice to the cases in which, indeed, scientific theories have merely an instrumental value, and incorporate elements constructed without causal constraints. Chapter 7 illustrates such a case (the S-matrix theory of strong interaction) and pleads for a selective scientific realism.
Acknowledgments
I am very much obliged to my doctoral supervisor, Professor Wolfgang Spohn, for his invaluable assistance. His criticism and demand for clarity and precision was doubly outweighed by his patience and confidence in the merits of my work. My gratitude is also extended to professors William Newton-Smith, James Robert Brown, Michael Devitt, and Gereon Wolters for their advice and guidance through the intricate paths of scientific realism. Ludwig Fahrbach and Erik Olsson provided me with welcome criticism and commentary, either by reading various sections of my dissertation, or through conversation about its contents.
This dissertation would not have reached completion, were it not for the fi-nancial support of the Open Society Institute and the Herbert Quandt Stiftung.
I am thankful to Dr. Gerhild Framhein for her generosity and understanding, as well as to Professor Andrei Hoisie. I am in debt to the DAAD for making possible my academic contact with Konstanz University.
I am also very much indebted to Professors Erhard Roy Wiehn and Kath-leen Wilkes for their moral support.
Finally, I wish to thank my friends Debbie Allen for improving the English standards of the present work, and Sascha Wolff for his patient LaTex advising.
Special thanks to my friend Till Lorenzen for all his support.
Chapter 2
The Success Arguments for Scientific Realism
It is virtually incontestable that science is an immensely successful enterprise.
First, science is successful in entailing successful predictions. Second, scientific methods have proven to be effective in generating successful theories. Let us call the former aspect the empirical success of science, and the latter, the methodological success of science. According to the scientific realist, both sorts of success are non-trivial facts. They demand explanation: Why do scientific theories tend to produce correct observational predictions and to deliver adequate explanations of observable phenomena? By which means is scientific methodology so good at forming successful belief systems?
The reason why the scientific realist thinks that the success of science un-dergirds his doctrine is that he arguably has the best explanations for both the empirical and the methodological success of science. Indeed, his argu-mentation relies on an inference to the best explanation (henceforth IBE): the best explanation for the fact that scientific theories are empirically success-ful is that theoretical terms typically refer, and that theoretical statements are approximately true or truthlike. Similarly, the best explanation for the methodological success of science is that scientific methodology is reliable (in a sense to be explained in subsection 2.4.2).
It is important to emphasize that the explananda of the two IBEs are different. On the one hand, the empirical success argument seeks to explain the success of theories in systematizing and explaining phenomena, and in making highly confirmed predictions. On the other, the methodological success argument attempts to explain the success of scientific methods in producing successful theories.1
1As we shall see in section 2.2, one antirealist argument capitalizes on the alleged insuffi-cient stringency of IBE at the methodological level.
Second, the explanandum of the empirical success comprises two parts, asserting, respectively, that (i) theoretical terms are referential, and (ii) the-oretical statements are approximately true. I would like offer two remarks about them.
The first and general one is that, in line with Devitt (1984; 2003), I take it that it is not essential to state the argument by means of the terms ‘refer’
and ‘true’:
...such usage should be seen as exploiting the disquotational properties of the terms with no commitment to a robust relation between language and the world. The realist argument should be that success is explained by the properties of unobservables, not by the properties of truth and reference. So the argument could be urged by a deflationist. (Devitt 2003: Fn. 11).
I shall not go into the details of any specific theory of truth, since I take it that no particular view of truth is constitutive of realism – see section 1 in the introductory chapter. I subscribe to Devitt’s (1984: 4) Third Maxim that requires us to settle the realism issue before any semantic issue. The benefits of disquotation also extend to the concepts of approximate truth and truthlikeness. Instead of talking about the approximate truth of the sentence
‘aisF’, we can just talk ofa’s approximately beingF. However, with respect to approximate truth and truthlikeness, I often prefer to talk in these terms instead of disquotation. The reason lies in the fact that, on many occasions, we want quantitative comparisons of truthlikeness, and that, as such, disquotation would only make them more awkward. Besides, I also believe that we have a robust and serviceable account of truthlikeness given by Niiniluoto (1999) (see A.2).
My other remark about the distinction between the two parts within the ex-planandum of the empirical success of science is that each of them corresponds to a different version of realism. The claim that most (essential) unobserv-able entities posited by scientific theories exist independently of our minds, language, and representations defines the doctrine ofscientific entity realism.
While entity realism is committed to science’s being mostly right about the en-tities it posits, it is partly noncommittal on the truth values of those theoretical sentences describing the properties of entities and the relations between them.
Nonetheless, many realists defend a logically stronger version of scientific re-alism, committed not only to theoretical entities, but also to the descriptions of their properties. This is the doctrine that Devitt callsstrong scientific real-ism: “most of the essential unobservables of well-established current scientific theories exist mind-independently and mostly have the properties attributed to them by science.” (Devitt 2003). Since strong scientific realism seems to be
embraced by most self-declared scientific realists, I label it scientific realism and distinguish it from mere entity realism. It is clear that scientific realism implies entity realism, but not the converse. Moreover, the best-known ad-vocates of the latter (Hacking 1983; Cartwright 1983) explicitly argue against what they calltheory realism – realism about scientific laws – thereby denying the scientific realist claim complementary to entity realism.
As we have seen, the argumentation for scientific realism proceeds by IBE.
This implies that any IBE in favor of scientific realism will also support entity realism. Yet, entity realism enjoys supplementary support from the so-called experimental argument, which will be the subject of the next chapter. The efficiency of IBE in defending scientific realism has been detracted in two im-portant ways: first, some anti-realists (van Fraassen (1984; 1989); Fine (1984;
1986; 1991)) levelled objections of principle against IBE-based arguments, de-nouncing them for being context-dependent, inconsistent, and viciously circu-lar. I dismiss these objections in 2.2 and 2.4. A different kind of criticism concerns IBE’s specific role in the defence of scientific realism. Laudan (1984) deployed the most extensive attack of this kind. I argue against it in section 2.3.
Let us now outline the argumentative strategy of this chapter. Section 2.1 presents several explanationist arguments for the empirical success of science:
Putnam’s (1975; 1978) ‘no miracle argument’ (NMA), which is the most popu-lar formulation of an IBE-based explanation of the success of science; Smart’s (1963) ‘no cosmic coincidence argument’, and Maxwell’s (1970) argument from the empirical virtues of realistically interpreted theories; and finally, my argu-ment based on the exclusive ability of realistically interpreted theories to give causal explanations. Section 2.2 investigates the general objections against IBE, while 2.3 continues with a detailed discussion of the alleged inability of IBE to connect the empirical success of science with the approximate truth of theories. Section 2.4 discusses Boyd’s (1984; 1985) explanation of the method-ological success of science, as well as Fine’s replies to it.
2.1 The “No Miracle Argument”
The most famous argument from the empirical success of science is Putnam’s (1975) ‘no miracle argument’ (henceforth NMA). NMA claims that the predic-tive success of scientific theories is best explained by their being approximately true:
The positive argument for realism is that it is the only philosophy of science that does not make the success of science a miracle. That terms in mature scientific theories typically refer (this formulation is due to
Richard Boyd), that the theories accepted in a mature science are typi-cally approximately true, that the same terms can refer to the same even when they occur in different theories – these statements are viewed not as necessary truths but as parts of the only scientific explanation of the suc-cess of science, and hence as part of any adequate description of science and its relations to its objects. (Putnam 1975: 73)
The argument emphasizes the overwhelming improbability (indeed the miracle) of any explanation which would not rely on the referentiality of theoretical terms and on the approximate truth of scientific theories.
Putnam does not bother here to distinguish between entity realism and scientific realism. However, if cogent, his argument will defend both the claim that theoretical terms typically refer, and the logically stronger one that the theories themselves are approximately true.
NMA is obviously an IBE-based argument: to accept that theoretical terms refer, and that scientific theories are approximately true isthe best explanation of why phenomena are the way they are predicted by those theories. This, according to NMA, is not only a good explanation of empirical success, but also the best explanation we have for it. Suppose we ask, for example, why are observations that scientists report onas if there were atoms? The realist answer is: because there are atoms and – stronger claim – because the atomic theories are approximately true. Were this not the case, what else but a miracle would explain the empirical success of theories? (See section 3.1 for a historical case study of modern atomism).
As it can be seen, the explanans of NMA is not the strict truth of sci-entific theories, but their approximate truth, or truthlikeness. Strict truth deductively entails the truth of all consequences of a given theory. However, theoretical descriptions are most of the time only approximately correct or truthlike. Approximate truth and truthlikeness are not uncontroversial tions. Among others, Laudan (1981) maintains that these are undefined no-tions, and accordingly disapproves the realist’s explanatory appeal to such
“mumbo-jumbo” (1981: 32). However, for one thing, the notion of approx-imate truth has a quite strong intuitive support. As Devitt (2003) notes,
“science and life are replete with such explanations; for example,a’s being ap-proximately spherical explains why it rolls.” For another, it is surely not the case that approximate truth is an undefined notion. Quite the contrary, there is an appreciable literature approaching a quantitative definition of approxi-mate truth via its related concept, truthlikeness – see, among others, Oddie (1986), Kuipers (1992), and Niiniluoto (1987; 1999). As far as I am concerned, I favor Niiniluoto’s similarity approach (see the Appendix). I take it to be a
“science and life are replete with such explanations; for example,a’s being ap-proximately spherical explains why it rolls.” For another, it is surely not the case that approximate truth is an undefined notion. Quite the contrary, there is an appreciable literature approaching a quantitative definition of approxi-mate truth via its related concept, truthlikeness – see, among others, Oddie (1986), Kuipers (1992), and Niiniluoto (1987; 1999). As far as I am concerned, I favor Niiniluoto’s similarity approach (see the Appendix). I take it to be a