Temporal inconsistencies

Let us once again consider some facts about dinosaurs. Let D be the fact of dinosaurs’ existence. Let also D0 be the fact that D occurs at time t0

(Dinosaurs existed in Mesozoic), and not-D0 the fact thatDdoes not occur at t₀ (Dinosaurs did not exist in Mesozoic). Let alsoC₁(D₀) be the fact thatD₀ was constructed at timet1 (say, 1970), and C2(not-D0) the fact that not-D0

was constructed at timet2, wheret2 > t1 (t2 is, say, the year 1980). Thus the world att₁ has a past containing the event D₀, and the world att₂ has a past containing the event not-D0. But since pastness is transitive, it results that the world at t2 contains in its past both D0 and not-D0. That is, the world in 1980 contains both the fact that dinosaurs existed in the Mesozoic era, and the fact that dinosaurs did not exist in the Mesozoic era. Consequently, SMC faces a diachronic inconsistency.

Perhaps these examples which allude to the creationist debate seem con-trived. However, a glance at the constructivist literature gives us genuine examples of the sort we want to illustrate. Latour and Woolgar (1986) tell us that it became true in 1969 that TRH (tyrothropin-releasing-hormone) has the chemical structure Pyro-Glu-His-Pro-NH2. Before 1969 there was no fact of the matter whether TRH had or had not that chemical structure. In terms of the previous scheme, the world in 1970 contained both the fact that before 1969 there was no matter of fact whether TRH was Pyro-Glu-His-Pro-NH2, and the

fact that from 1969 on, TRH had been Pyro-Glu-His-Pro-NH2. Obviously, this is a temporal inconsistency of the same sort.

A typical constructivist retort would be that this argument stems from the difficulties to articulate the constructivist view. Indeed, some philosophers have suggested that this trivial paradox points to an intrinsic problem of the modality and tense structure of assertions of fact – e.g. Hacking (1988: 281).

Hacking blames the inability of natural language to express the complex sit-uations arising from social construction. Nevertheless, no concrete proposals of a better temporal logic are available. Additionally, the selected examples can easily be understood in terms of our good old temporal logic. Instead of the awkward formula that it became true in 1969 that TRH had always been Pyro-Glu-His-Pro-NH₂, we can simply say that it was always true that TRH is Pyro-Glu-His-Pro-NH2, although scientists discovered this fact only in 1969.

But of course, to admit this is to admit the temporal incoherence of SMC.

Let us now summarize the inventory of the species of constructivism which managed to pass through the sieve of the previous arguments. We saw that re-flexivity generates an infinite regress for SMC, but that it is undecided whether the regress in question is in general vicious. This gave SMC a pause, but not for long, since we afterwards saw that it encounters irredeemable spatial and temporal inconsistencies. Reflexivity is an insuperable problem for EC and re-veals SC to be either incoherent, or irrational. Under the bottom line, only a moderate metaphysical constructivism (MMC), according to whichsome facts about the world are constructed, can overcome these objections. The claim is rather disappointing for someone expecting more spectacular deeds from social constructivism. To say that some facts are constructed would barely make a headline. However, as will be seen in the next chapter, MMC can have an explanatory role in the philosophy of science.

Chapter 7

A Case for Selective Scientific Realism:

S-Matrix Theory

Scientific realism is often taken to be an overarching doctrine, claiming to account for the great majority of cases of genuine science. Recall our working definition of scientific realism: most of the essential unobservables of well-established current scientific theories exist mind-independently. I took pains to defend this definition and shall stick to it. Nonetheless, I do not believe that scientific realism should be an overarching doctrine. On the contrary, it should beselective.

I delivered positive argumentation for scientific realism (see the success arguments), and defended it from various attacks – in particular, from the un-derdetermination argument and from the implications of the strong versions of social constructivism. However, as admitted in 2.1.3, instrumentalism – realism’s archenemy – stands as a proper account for appreciably many scien-tific episodes. We touched upon the tendency of natural science to embrace more and more abstract formalisms intended to serve as models, i.e. as struc-tures claiming empirical adequacy, and conjectured that the more abstract the formalism of a theoretical science, the more inviting it is to instrumentalist attitudes. We argued that the a framework of a causal explanation theory is indicative of the presence of a theory demanding scientific realism. The point is also expressed by Campbell: “causal explanations identify the real agents which are producing the real effects we attempt to explain.” (Campbell 1994: 31). By contrast, when a causal framework is absent, an instrumentalist understanding of a theory’s claim may well be accepted.

Specific to an instrumentalist stance is the presence of abstract theoret-ical models, of theories involving no more than the belief in their empirtheoret-ical adequacy. What matters is whether they are adequate to the task for which they were devised. In laboratory jargon, they are supposed ‘to do the job’,

whatever that might be: to solve a previously unsolved problem, to support the discovery of new principles, to make relevant predictions, etc. From our standpoint, the most important aspect is that no ontological commitment to the posited entities and explanatory mechanisms is required.

It is comfortable for the realist to consider that if there is anything success-ful about such theoretical zombies, it will come to be embedded in ‘respectable’, approximately true theories. As Ellis phrases it, “many scientific realists en-visage the eventual replacement of model theories by systemic ones in which all of the laws and principles are just true generalizations about how actual things behave.” (Ellis 1985: 175). However, they seem to be pointing in the wrong direction:

a great deal of theoretical scientific research goes into devising increas-ingly abstract model theories, and relatively little into reducing the degree of idealization involved in our theories in order to make them more re-alistic. ...basic theoretical development in science tends, if anything, to proceed in the opposite direction – to greater abstraction and generality.

(Ellis 1985: 175)

To be clear, we maintain the claim that virtually all well-established theories are approximately true. The point is that an important part of science is developed via theoretical structures of instrumental value. Moreover, these theories cannot be ‘domesticated’ in the sense of being embedded in well-established realistic theories.

Because of the meager causal constraints, abstract model theories are pri-marily subjected to internal, coherence demands. As such, they are con-structed within a space of theoretical tolerance, which allows for external (e.g.

social) factors to intervene in the process of theoretical construction. An his-torical survey of an episode in modern high-energy physics (HEP) helps to illustrate this: the S-matrix program and its development between 1943 – when Heisenberg introduced the concept – and the late 1970s, when S-matrix was by and large abandoned. I present the S-matrix theory as an example of a program which failed without being falsified. As has happened more than once in modern theoretical physics, the fate of S-matrix was not decided by empirical disconfirmation. Its fate was decided rather by ‘external’ factors such as the particular expertise and philosophical view favored by the dom-inant part of the HEP community. The claim is not that S-matrix theory (henceforth SMT) could not have been falsified by any imaginable experiment.

The point is rather that after several decades of empirical and institutional success, SMT was abandoned mainly due to factors other than the internal logic of theoretical physics.

The exposition of the historical facts is substantially informed by James Cushing’s (1990)Theory Construction and Selection in Modern Physics. The S-Matrix.

7.1 The S-Matrix Theory (SMT):

a historical case study

The story of the S-matrix is inseparably related to the evolution of quantum field theory (QFT). It is therefore useful to start with at least a sketchy pre-sentation of the latter, if we are to have an intelligible perspective on the former.