دانلود رایگان ترجمه مقاله نیمه رئالیسم – الزویر 1998

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Semirealism

2. Entities: Detection Properties, Auxiliary Properties

Entity realism holds that most of the entities referred to in scientific theories are actual inhabitants of an external, mind-independent reality. It is this aspect of theory—the existence of particular theoretical entities—that we may reasonably believe to be true. ER has proven uncontroversial (so long as no one invites the opinion of the idealist or solipsist) where macroscopic objects are concerned, for it is claimed that the reality of such objects is clearly demonstrated by simple ostensive presentation. Those objects too small to be detected by the naked eye, on the other hand, have suffered remarkable discrimination. Recent debate has addressed van Fraassen’s (1980, p. 12) claim that acceptance of a scientific theory entails, or should entail, only the belief that it is empirically adequate, meaning that ‘what it says about the observable things and events in this world is true’. Newton-Smith (1981, pp. 19–28) discusses the contention that claims concerning unobservables are riskier, given that their detection depends upon sophisticated equipment and theoretical assumptions, and that for this reason observables are epistemically privileged. The case, however, for denying that different epistemic attitudes with respect to entity existence should be brought to bear on information derived from the employment of human sensory modalities in isolation, as opposed to information obtained from combinations of human and technological sensory machinery, has been made persuasively. Thus, resolving not to go the way of discrimination, let us invoke a commonplace regarding why it is that we believe in the objects of our perceptions: we believe that our sensory experience is brought about by the very things of which we have experience. Objects exist, and they affect us in such a way that we are confident, by virtue of their affecting us (us perceiving them), that they exist. Admittedly, this is vague, but it may be the best that we can do. At the very least, let us elaborate on what it might mean to ‘be affected’ or to ‘perceive’ in the manner indicated. This we do in terms of a familiar story about how empirical information is acquired by the human subject: things happen in the world, some of these things interact with our sensory apparatus, sensory machinery translates this information into signals which are processed by the brain, we perceive. In other words, information about real entities in the world is communicated to us by a causal chain of events; it is on the basis of such causal chains that we believe these entities to exist. We can and do believe in the existence of external objects pre-philosophically, but once we stop to justify such beliefs, we are driven to explanations in terms of causal interactions. The version of the pessimistic induction alluded to above seemingly represents no threat to ER, since this argument reasons from the falsity of past theories, but not specifically past failure of reference on the part of theory terms, to doubts about current theories. Let us, however, intensify the challenge of the pessimistic induction. Consider the idea that the meanings of entity terms are to some extent defined by the theories in which they occur. How can we ascribe reality to some object x, if it turns out that we were, and may well now be wrong about what x is? Is it intelligible to assert that x exists, and yet be open to the possibility that our conception of x (the set of defining properties with which a particular theory picks out x) may change? If the meaning of ‘x’ changes, to what extent can we be said to be discussing the same entity? According to certain referential models of meaning (discussed by Kitcher (1993, pp. 76–78), and earlier by Putnam (1975, pp. 249–251, 269)), the set of descriptions with which any given referent is picked out may evolve, while the collection of modes of reference continues to refer to the same entity. It is this picture of meaning that we adopt when we say that Thomson, Lorentz, Bohr, and Millikan were all concerned with the same entity: the electron. To whatever extent our concepts and detections of observable and/or unobservable objects are theory laden, this should not stand in the way of legitimate beliefs in the existence of putative entities, however we may conceptualize them with different theories. Thus our beliefs with respect to the existence of causal agents need not suffer with changes in our attitudes toward the theories in which such agents play a role. And what about that rogues’ gallery of non-referring entity terms from celebrated theories of the past—‘phlogiston’, ‘ether’, and their ilk—do they not speak volumes against the wisdom of adopting ER?2 If there is anything intrinsic to practices of detection that suggests which causal agents will survive theoretical changes, it is the possibility of corroboration by alternative forms of detection. The greater the extent to which such corroboration takes the form of theoretically independent evidence, the greater its power of confirmation.3 Highly corroborated entities are vindicated and take their place in our ontology; those that cannot be substantiated by this form of risk management more often than not take their place in the ‘failures’ chapter of our history of scientific ideas. It may be instructive to think about why the above reformulated version of the pessimistic induction is generally targeted at unobservable entities. I suggest the reason is that our prima facie intuitions lead us to believe that unobservables are particularly susceptible to such arguments. Thus, it is thought obvious that both my opponent in the debate, the president of the flat earth society, and I refer to the same object when we speak of ‘the earth’. Here we identify an entity despite differences in associated properties, about which we could argue all day. The same, of course, applies to the example of different theorists and their views on the electron, and to other corroborated unobservables, thus telling against our prima facie intuitions. But now we seem to have muddled things up, for surely we identify objects on the basis of certain properties—namely, those described by causal processes in virtue of which entities interact with our means of detection—and yet simultaneously we speak of identifying objects in spite of differences in the properties we attribute to them. Just what sorts of properties are we talking about here? In his discussion of ER, Devitt (1991, p. 46) contrasts the position with what he portrays as the alternative for the realist, ‘theory realism’, which he describes as ‘a stronger metaphysical doctrine’ according to which ‘science is mostly right, not only about which unobservables exist, but also about their properties’. But as the confusion cited above suggests, this may be painting with too broad a stroke. A more refined consideration of properties is required if we are to make sense of the seeming tension between identifying an object and differing about its attributes. For one thing, it is not clear that all properties are of the same type; distinguishing kinds of properties may in fact distinguish forms of realist commitment. What sorts of properties allow us to establish the existence of an entity? The answer, according to the account given above, is those properties which delimit causal interactions and which are, by virtue of this fact, exploited by us by way of detection. We infer entity existence on the basis of perceptions grounded upon certain causal regularities having to do with interactions between objects. Let us thus define detection properties as those upon which the causal regularities of our detections depend, or in virtue of which these regularities are manifested. Auxiliary properties, then, are those associated with the object under consideration, but not essential (in the sense that we do not appeal to them) in establishing existence claims. Attributions of auxiliary properties function to supplement our descriptions, helping to fill out our conceptual pictures of objects under investigation. Theories enumerate both detection and auxiliary properties of entities, but only the former are tied to perceptual experience. Perhaps an example will clarify the property distinction at issue. In a paper on structural realism, Worrall (1989) features the case study of transition from the wave optics of Fresnel to the electromagnetic theory of Maxwell. Worrall considers a set of equations developed by Fresnel, relating intensities of reflected and refracted light to that of an incident beam passing from one medium into another of different optical density.