The induction to Convergent Realism would fail if it could be shown that the 'pragmatic' property of manipulative efficacy of a theory/model is simply a special case of the logical property of empirical adequacy. It might seem that it would be enough to point out that manipulative efficacy is revealed in a theory-guided material practice while empirical adequacy is revealed in discursive procedure the criteria for the correctness of which are logical. The practice and the procedure are of radically distinct categories, and therefore irreducible.
But it might be objected that this short way with the problem overlooks the fact that the claim that a practice is efficacious is supported only if the outcome, the phenomenon produced to order, so to say, fulfils certain criteria, that is it is a phenomenon of the type to be expected.
These criteria are defined discursively, by the same hypothetico-deductive procedure that would have established empirical adequacy.
The reply to this objection takes us to the heart of the argument. There are two possible hypothetico-deductive procedures which would permit an efficacious manipulation to count as a test of empirical adequacy of the theory which guided it. One case is when the empirical adequacy of a mere Humean correlation between implementation of the procedure and its outcome provides the hypothetico-deductive structure, on the basis of a 'coveting law'. Thus the Stern-Gerlach experiment merely demonstrates the empirical adequacy of the 'law' that activating a certain kind of circuit is correlated with a characteristic change in the pattern of light on a screen. But this requires physics to include an indefinite number of ad hoc 'laws', involving standard physical concepts, which are 'out of step' with such well-established principles as those I have called Boyle's and Faraday's Principles, each of which is a summary of a well-founded branch of physics. If indeed one were to accept the 'coveting law' reduction of the Stern-Gerlach experiment it would be a disconfirmation of the Faraday Principle, and so effectively an abandonment of electromagnetism. But this point might be conceded while the determined reductionist could argue that manipulative efficacy should be taken as test of the empirical adequacy of the full-scale theory/model/type-hierarchy, and no more than that. But in that case the reductionist must invoke either the Boyle or the Faraday Principle (or something like it) as part of the theory. But this is tacitly to accept the ontological account of the efficacy of the manipulation with respect to the Humean phenomenological correlation revealed in the Stern- Gerlach experiment between activated circuits and reoriented images. The empirically well supported Boyle and Faraday Principles block the use of Clavius' Paradox (underdetermination of theory by data) to undercut the proof of the ontological assumptions involved in the experimental procedures by reference to the efficacy of the manipulation.
So either the putative reduction tends to privilege a weak phenomenological correlation over well-established laws and principles, or it involves tacit acceptance of an irreducible ontological assumption. This assumption amounts to the principle that what is being manipulated by the overt procedure is a covert structure, process, entity or property. The reduction is either ad hoc or ontologically concessive. So it fails to convince in either case.
A different kind of defence of the autonomy of the manipulative efficacy of procedure as an
Policy Realism 61
independent criterion for the verisimilitude of the model that guides it, invokes the general incompleteness of the discursive presentation of many theories. There are many procedures that can be demonstrated to be efficacious by 'rule of thumb' in the absence of a discursive presentation of the theory sufficiently articulated to permit a water-tight hypothetico-deductive demonstration that the phenomena produced to order by the manipulation are proofs of the empirical adequacy of the theory. Medical science is full of examples of the efficacious but indirect manipulation of unobservable structures, processes, entities and properties in the admitted absence of a well-articulated hypothetico-deductive derivation of propositions describing the results.
We can now rank the three criteria on which the piggy-back sequence of inductive arguments was constructed. Ontological plausibility is parasitic upon empirical adequacy and manipulative efficacy, in that an exotic type-hierarchy which is ontologically innovative, is defensible for verisimilitude in the sense of Aronson, the sense made use of throughout this paper, just in so far as instantiations of its subtypes meets the primary criteria, as we have just identified them. This step provides a philosophical ground for the defence of the important thesis that ontologies have an empirical basis, even when none of their subtypes, in a Way-style presentation are instantiated in entities that can that can be commonly be observed. Without this step the inductive argument for Convergent Realism, in the version defended here, would be open to the objection that it is implausibly ontologically conservative.
I have tried to show that induction from 'observed' cases of correlation between the satisfaction of the three criteria based on the 'evidential' properties of theories and the 'projectible' property, that is between the satisfaction of the criteria for 'good theory' and the demonstrable verisimilitude of the model of the theory, to unobserved cases, that is cases in which the verisimilitude of the model cannot be assessed empirically, is reasonable. Theories which meet the three criteria are more likely to be verisimilitudinous than those which do not, and the more a theory meets them relative to the performance of a rival, weaker by the same criteria, the more likely is the model of the former than the latter to resemble the relevant aspect of reality. Since this is an inductive argument, the future of science may throw up a countervailing multitude of cases that defeat the induction. I hope to have shown the inductive form of argument in this context is rational. It is another matter to accumulate sufficient evidence for Convergent Realism.
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CHAPTER FIVE
M O D E L S A N D T H E R E A L I S M D E B A T E S
In recent years we have all come to see that 'realism' is not the name of one philosophical position, even within the philosophy of science. Nor is there just one range of arguments for and against a realist position. Nevertheless, 'realism' and 'anti-realism' are genetic terms for clusters or families of doctrines for each of which there are loosely related ensembles of arguments. Part of my purpose in writing Varieties of Realism (1986) was to demonstrate that there was a significant polarity in the cluster of realisms, Realist doctrines differed not only in their metaphysical underpinnings, but also in their relative vulnerability to f a i r y traditional anti-realist arguments. At the time I wrote that book I thought that no one realist doctrine could be successfully defended for the physical sciences at every stage of their development. I now see that there are ways in which the two main varieties of realism I want to defendmviz, a strong 'policy realism' and a weak 'convergent realism' - - are inter-related, though they are not, I believe, either mutually reducible or simultaneously applicable.
The first step in clearing one's mind on the nature of realism should be an attempt to catalogue the most obvious varieties. For the purposes of this commentary I want to highlight a major division into epistemic approaches and pragmatic approaches.
1. The epistemic approach uses concepts like 'truth', 'falsity' 'verisimilitude' and so on to characterize its variety of realism. The most conspicuous modem form of the epistemic approach is 'convergent realism'. According to this approach the greater predictive success (empirical adequacy) of a theory, the more truly it depicts the w o r d (the greater its verisimilitude). By varying one's conception of empirical adequacy, say by taking it as persistent survival in the face of vigorous attempts at falsification, one can arrive at a cluster of 'realisms' that includes the doctrines of both Newton-Smith and Popper.
In common to all versions of the epistemic approach there is the Principle of Bivalence.
According to this principle the statements of a theory are true or false by virtue of the way the world is whether we know it or not. To apply the principle of bivalence to scientific research we need another principle to support claims for verisimilitude for as yet untested statements. Of equal prominence then in recent discussions of realism has been the argument to the best explanation. This argument has a mundane use in which we say that the best explanation of the predictive success of this or that theory is that it is true. And it has a transcendental use in which we say that the best explanation of the long-run success of the physical sciences is that science, as a whole, is getting nearer the truth. There are, it is not hard to show, alternative explanations of this success, that are not so good ~ for instance, that the success is the result of a vast, long- running coincidence. Of course, much of the force of the argument hinges on the criteria for 'best'. Lipton (1985) has shown that there is an essential ambiguity in the criteria for 'best' which greatly weakens the argument.
2. The other pole is occupied by a family of positions based on pragmatic notions like 'intervention', 'manipulation', 'material practice', and so on. The concepts of truth and falsity give way to notions like reference and denotation. Science is seen as a practical rather than as a cognitive activity and its products as material things rather than propositions . . .
I have presented the two main families of realisms as polarities rather than antitheses. They interpenetrate one another to some extent. By treating the establishment of reference in terms of the satisfaction of certain propositional functions, the relation of reference is transformed from a physical link between an embodied scientist and a material being into a semantic indication
64 The Realism Debates
determined by a set of true and false propositions. On the other hand, polar oppositions germane to practice, such as success or failure, seem to mimic the polarity between truth and falsity.
Realists of the epistemic persuasion seem to take for granted that the aim of science is the enunciation and testing of laws. If the truth of laws eludes us by virtue of traditional objections to inductive universalizations, then perhaps we can be sure of the falsity of some conjectured laws.
The tendency to focus on laws in this way is closely correlated, not surprisingly, with a tendency to take theories simply in their discursive form, as sets of propositions ordered by the deducibility relation. However different their epistemologies may have been, this conception of theory is shared by both Hempel and Popper, and it accounts in part for the disparities between their philosophies of science and scientific practice.
For those of the 'pragmatic' persuasion the role of laws is secondary to that of interlocking structures of analogies, models and metaphors in the organization of scientific knowledge. The Hempel-Popper deductivist conception of theory is seen as the realization of a rhetorical convention for scientific writing rather than as the necessary basis for an account of scientific cognition and of the genesis and development of scientific theories in the thought collectives of real science. Theories, as philosophers have tended to analyse them, are momentary abstractions from evolving theory-families. The theory-family idea has appeared from time to time in different guises. Whewell wrote of 'the development of an idea'; Ludwig Fleck used the expression 'thought-collectives'; Thomas Kuhn called such entities 'paradigms' and Lakatos described them as 'research programmes'.
Given the vulnerability of the epistemic variety of realism to quite simple sceptical arguments can we find a better line of defence for the pragmatic variety? If we can, how can at least some of the valuable aspects of the epistemic variety of realism be reconstituted? I have in mind such concepts as 'scientific progress', 'increasing verisimilitude', and so on.
The historical pageant of science has been presented as if it were a linear progress from the verifying or corroborating of the laws of the observed to those of the unobserved to those of the unobservable. At each stage greater hazards to fortune are offered in that subsequent work stands a greater chance of revealing inadequacies in what has gone before. But there were richly elaborated accounts of the transcendental realm as integral parts of physics long before the present era. A case can be made for saying that the overall pattern of thought in the physical sciences has changed very little, despite huge changes in content and in the sophistication of the experimental equipment and of the mathematical tools. A methodological insight of Archimedes or of Robert Boyle ought to hold good for today's physics. The physics of the past ought to be as good a test object for efforts to make judgements about it intelligible under our alternative realisms as contemporary physics.
Be that as it may, any variety of realism needs a platform in perception relative to which the status of beings described by theory, but which are currently unobserved or even unobservable, can be assessed. If the apparatus I see before me is a subjective phenomenon, hazardously projected into interpersonal 'space', all further discussion about the fights and wrongs of realism is pre-empted.
To escape the traditional shackles of phenomenalism, I turn first to the psychological work of J. J. Gibson, not only for its technical sophistication and its remarkable experimental programme, but also for the depth of the new conceptual system he proposed. In sharp contrast to the traditional picture of the perceiver as the passive recipient of stimuli-producing sensations, integrated thereafter into perceptual structures, Gibson presented his vision of the human perceiver as an active being exploring his or her environment (1979).
The longest-running threat to a realist reading of natural science has been the idea that perception is, at bottom, subjective. Ixx:ke's ideas and Hume's impressions are modes of the consciousness of individual people, strictly incomparable with the ideas and expressions
Policy Realism
65experienced by anyone else. It is an easy step forward into Machian sensationalism or back into Plato's cave. How can it be known that there is a common world which scientists collectively study by experimentally exploring it and theorizing about it in a way that is indirectly disciplined by the results of these explorations? At best the existence of this world is a hazardous assumption. In response to this, it could be claimed that we have little idea what it would be like to discover that our hypothesis of a common world and of a community of scientists like ourselves was false. But this kind of move, however nicely elaborated, is not as good as a positive demonstration of the psychological plausibility of the common-sense view that there is a common world and that we jointly explore it.
The traditional view took it for granted that perception is the result of a synthesis of atomistic sensations which are presented subjectively. Gibson held that sensations had little importance as such in the perceptual process. He believed that our senses were integral parts of perceptual systems, which had evolved to explore the ambient flux of energy in which we ourselves cast a shadow, so to speak, and to detect certain higher-order invariants in that flux.
These invariants were the effects of physical objects. Gibson called this 'pick up' and the whole process 'direct perception'. There was no synthesis and nothing mediated in any sensory way between things and people. This robust account was supported by a huge range of ingenious experimental evidence . . . .
General ecology is in debt to von Uexkull (1909) for a number of refinements of the idea of an environment. He introduced his distinctions to try to differentiate the various ways that animals and plants are integrated into the physical world. For the purposes of this discussion his most important contribution was the concept of Umwelt. The Umwelt of a species of organism is that part of the material world that is available as a living space to the members of the species by virtue of their specific modes of adaptation, such as distinctive perceptual and manipulative capacities. The same 'total' world contains any number of possible Umwelten. Gibsonian ecological psychology encourages us to think of the physical world we share as human beings, as an Umwelt. It is the living space made available to people through their perceptual and manipulative capacities. If Gibson is fight it is the human Umwelt which is the object of study of the physical sciences. I propose to treat experimental apparatus and the advancing techniques of observation as prosthetic extensions of or as 'organs' added to our perceptual systems e.g.
telescopes, as Gibson saw them. It would follow that the human Umwelt is changing historically.
It would be in the spirit of Gibson's psychology of perception to say that scientists are enlarging or diminishing the human Umwelt, rather than that they are revealing more of a universe which was, neutrally, there. Of course, the universe is richer than the current Umwelt, and I am the last to deny that there is scientific progress.
According to Gibson the most important properties observable in the Umwelt, that is, available to us by the use of our perceptual systems actively to explore the ambient flux, are such attributes as durability, solidity and so on. These are properties of the Umwelt but affordances of the 'total' world, the universe. Why 'affordances'? Because they are material dispositions relative to human activities and practices. 'Using' is the activity correlative to 'durability'. A paved patio affords walking and a particle accelerator affords the photographing of tracks. I do not think it is doing too much violence to Gibsonian ideas to go a step further and take the tracks so photographed as affordances of the apparatus. In the advanced sciences the apparatus with which we manipulate the material world also delimits it as an Umwelt.
According to convergent realism, successive theories are better and better approximations to a perfect representation of a fixed and given but partially unknown world. But in the Gibson-yon Uexkull framework I have been putting together there is an enlarging human Umwelt which is that aspect of the 'total' world that our perceptual systems and the apparatus by which we have extended and enlarged them, makes available to us. In one version or another this is an old idea.
66 The Realism Debates
For Vico and for Kant it was the root of the intelligibility of society and of empirical experience respectively.
The world will not always afford what we expect (the thin ice that does not, after all, afford walking; the gold that was to be the outcome of alchemical manipulations). This seems a natural way of expressing an insight but ultimately it is an unsatisfactory way of talking. We should not say that the world does not afford these activities or products. There would be no walkability to afford or not to afford were the vertebrates to be wholly avian or aquatic. We now know that the world does afford gold under another manipulative procedure. This is the kind of relativism which I believe Niels Bohr was trying to express in his 'correspondence' principle. The occurrent properties of the world, the 'total' world, which ground the dispositions we ascribe as affordances, can never become available to us independently of the apparatus that we have the ingenuity and technical skill to construct. 'The limitations of my equipment are the limits of my w o r d ! ' . . .
A main thrust of my own point of view is against the assumption that the prime product of science and the main instrument of its creation of knowledge is the statement (or proposition).
Before the proposition is the 'scientific act' (cf. Bachelard 1934, p. 11), a purposeful intervention into a natural system, guided by theory and assessed by reference to criteria of practical success or failure. Of course, theories are cognitive entities. My point is that it is not their truth or falsity that is of importance but their role as guides for action. The significance of such acts was seen clearly by Robert Boyle and exploited by him in his attempts to provide a firm empirical grounding for the 'corpuscularian philosophy'. A 'scientific act' has the following structures: a person acts on something, X, by the use of a certain manipulative technique, T. The point of the action is to manipulate something else, Y, through the medium of X. (A person heats a gas-filled tube so as to increase the mean kinetic energy of the molecules of the gas.) Our actor conceives this aim by virtue of tentatively holding a theory about X in which the concept 'Y' figures.
Changes in Y, that which has been indirectly manipulated, have effects Z, which a suitably alert and well-equipped person can observe or detect. (The increase in mean kinetic energy of the molecules of the gas results in an increase in pressure which changes the observable state of a manometer.)
What can now be said about the gas? The pragmatic claim is that we now know that X has a certain disposition, a Gibsonian affordance, that is, it affords Z on condition of manipulation T.
As an affordance this disposition cannot be reduced to Z, its overt display, since the human act, T, and perhaps a humanly devised detector, is required for the display. By performing scientific acts we can explore the boundaries of the human Umwelt. But we must bear in mind that the boundaries are joindy determined by the nature of the material world, whatever it is, and the range of manipulative techniques we have invented with which to explore it. For me scientific knowledge is not a collection of true beliefs (or if you prefer so far unfalsified conjectures) about X, Y and Z. It is the totality of scientific acts we know how to perform in an environment bounded by X, Y and Z.
The remarks above already foreshadow the ontological claim that a policy realist will make on the basis of successful scientific acts. The indirect target of the human manipulations, Y, must also be included in the human Umwelt. This needs argument and I propose to provide it in what follows. It was plainly assumed by Boyle and I hope to show that this was not without some reason. The theoretical sciences gain credit with us only in totalities of such acts, because our concepts of what we are manipulating occur intelligibly only within evolving theory-families.
The view I have called 'policy realism' requires that we read theories not as sets of true or false statements but as guides to possible scientific acts. Manipulative practices can be successful or unsuccessful. Theoretical concept denote states, structures, individuals, properties and processes which tentatively enter the Umwelt as manipulables. The metaphysical categories just listed are