Last time we discussed arguments due to Cartwright and Hacking for the entity realist position. Entity realism, as you recall, is the view that belief in certain microphysical entities can be (and is) rationally compelling. Cartwright argues that we are rationally required to believe in the existence of those entities that figure essentially in causal explanations that we endorse. (Van Fraassen's response to her argument is that since the endorsement of the explanation only amounts to accepting it--i.e., believing it to be empirically adequate--belief in the unobservable entities postulated by the explanation is not rationally required.) By contrast, Hacking argued that we are rationally required to believe in the existence of those entities that we can reliably and stably manipulate. He argues that once we start using entities such as electrons then we have compelling evidence of their existence (and not merely the empirical adequacy of the theory that postulates their existence). To make his case, he gives detailed descriptions of how we stably and reliably interact with things shown by optical microscopes, and with electron guns in the PEGGY series. The microscope case is especially interesting since it indicates that a person can acquire new perceptual abilities by using new instruments and that "observability" is a flexible notion.

The question that we will examine in the first part of the lecture today is whether Hacking's arguments do not simply beg the question against van Fraassen's constructive empiricism. Let us begin by discussing Hacking's argument that stability of certain features of something observed using different instruments is a compelling sign of their reality. In response, van Fraassen asks us to consider the process of developing such instruments. When we are building various types of microscopes, we not only use theory to guide the design, but also learn to correct for various artifacts (e.g., chromatic aberration). As van Fraassen puts it, "I discard similarities that do not persist and also build machines to process the visual output in a way that emphasizes and brings out the noticed persistent similarities. Eventually the refined products of these processes are strikingly similar when initiated in similar circumstances ... Since I have carefully selected against non-persistent similarities in what I allow to survive the visual output processing, it is not all that surprising that I have persistent similarities to display to you" (Images of Science, page 298). In other words, van Fraassen argues that we design our observational instruments (such as microscopes) to emphasize those features that we regard as real, and de-emphasize those we regard as artifacts. If that is so, however, we cannot point to convergence as evidence in the reality of those features, since we have designed the instruments (optical, ultraviolet, electron microscopes) so that they all converge on those features we have antecedently decided are real, not artifacts.

The principle that Hacking is using in his argument from stability across different observational techniques is that if there is a certain kind of stable input-output match in our instruments, we can be certain that the output is a reliable indicator of what is there at the microphysical level. Van Fraassen notes that, given the constraints that we place on design and that the input is the same (say, a certain type of prepared blood sample), it is not surprising that the output would be the same, even if the microstructure that we "see" through the microscope has no basis in reality.

Thus, Hacking is correct in seeking a more striking example, which he attempts to provide with his Grid Argument. (Here, as you recall, a grid is drawn, photographically reduced, and that reduction is used to manufacture a tiny metal grid. The match between the pattern we see through the microscope at the end of the process and the pattern according to which the grid was drawn at the beginning indicates both that the grid-manufacturing process is a reliable one and that the microscope is a reliable instrument for viewing microphysical structure. Thus, by analogy, Hacking argues that we should believe it what the microscope reveals about the microphysical structure of things that we have not manufactured.) Van Fraassen objects on two levels. First, he argues that argument by analogy is not strong enough to support scientific realism. For analogy requires an assumption that if one class of things resembles another in one respect, they must resemble it in another. (To be concrete, if the microscopic grid and a blood cell resemble one another in being microscopic, and we can be sure that the former is real because its image in the microscope matches the pattern that we photographically reduced, then we can by analogy infer that what the microscope shows us about the blood cell must be accurate as well.) To this van Fraassen replies, "Inspiration is hard to find, and any mental device that can help us concoct more complex and sophisticated novel hypotheses is to be welcomed. Hence, analogical thinking is welcome. But it belongs to the context of discovery, and drawing ingenious analogies may help to find, but does not support, novel conjectures" (Images of Science, page 299).

Discuss. What could Hacking reply? Consider the following: to show that an analogical inference is unjustified, you have to argue that there is an important disanalogy between the two that blocks the inference. Here the obvious candidate is that the grid is a manufactured object, whereas the blood cell, if it exists, is not. Since we would not accept any process as reliable that did not reproduce the macroscopic grid pattern we drew, it is no surprise that what we see through the microscope matches the pattern we drew--for we developed the process so that things would work out that way. However, we cannot say the same thing about the blood cell. Is this convincing?

Second, van Fraassen argues that to make Hacking's argument work we have to assume that we have successfully produced a microscopic grid. How do we know that? Well, because there is a coincidence between the pattern we observe through the microscope and the pattern we drew at the macroscopic level. Hacking's argument is that we would have to assume some sort of cosmic conspiracy to explain the coincidence if the microscopic pattern did not reflect the real pattern that was there, which would be unreasonable. Van Fraassen's response is that not all observable regularities require explanation.

Discuss. Might Hacking fairly object that, while it is true that not all coincidences require explanation, it is true that coincidences require explanation unless there is positive reason to think they cannot be explained. For this reason, he might argue that van Fraassen's counterexamples to a generalized demand for explanation, e.g., those based on the existence of verified coincidences predicted by quantum physics (the EPR type), are not telling, since we have proofs (based on the physical theories themselves) that there can be no explanations of those kinds of events. (Also, discuss van Fraassen's argument that to explain a coincidence by postulating a deeper theory will not remove all coincidences; eventually, "why" questions terminate.)

Now, we turn to the question of whether Hacking's claim that the fact that we manipulate certain sorts of microscopic objects speaks to their reality, not just the empirical adequacy of the theory that postulates those entities. Van Fraassen would want to ask the following question: How do you know that your description of what you are manipulating is a correct one? All you know is that if you build a machine of a certain sort, you get certain regular effects at the observable level, and that your theory tells you that this is because the machine produces electrons in a particular way to produce that effect. The constructive empiricist would accept that theory, too, and so would accept the same description of what was going on; but for him that would just mean that the description is licensed by a theory he believes to be empirically adequate. To infer that the observable phenomena that are described theoretically as "manipulating electrons in such-and-such a way to produce an effect" compels belief in something more than empirical adequacy requires assuming that the theoretical description of what he is doing is not merely empirically adequate, but also true. However, that is what the constructivist would deny.

Non-Empirical Virtues As A Guide To Truth: A Defense?

We have already examined in some detail van Fraassen's reasons for thinking that non-empirical features of theories that we regard as desirable (simplicity, explanation, fruitfulness) are not marks of truth, nor even of empirical adequacy, though they are certain pragmatic reasons for preferring one theory over another (i.e., using that theory rather than another). Let us look briefly at a defense of the view that "non-empirical virtues" of this sort are indeed guides to truth, due to Paul Churchland.

Churchland's view is basically that van Fraassen's argument against the non-empirical virtues as guides to truth can be used against him. Since we are unable to assess all the empirical evidence for or against a particular theory, we have in the end to decide what to believe based on what is simplest, most coherent or explanatory. This would sound much like the "forced choice" response that we looked at last time, except that Churchland is arguing something subtly different. He argues that van Fraassen cannot decide which of two theories is more likely to be empirically adequate without basing his decision on which of the two theories is simplest, most fruitful and explanatory, and so on. That is because the arguments that apply to the theory's truth with regard to its subject matter (available evidence in principle can never logically force the issue one way or another when it comes to unobservable structure), apply just as well to empirical adequacy. We'll never have complete knowledge of all observable evidence either, and so nothing compels us one way or another to accept one theory as empirically adequate rather than another (when both agree on what we have observed so far, or ever will observe). However, we cannot completely suspend belief altogether. Since that is the only choice that van Fraassen's reasoning gives us in the end, it ought to be rejected, and so we can conclude that non-empirical virtues are just as much a guide to truth as are what we have observed.

Churchland is a philosopher who works in cognitive psychology (with an emphasis on neurophysiology). He argues that we know that "values such as ontological simplicity, coherence, and explanatory power are some of the brain's most basic criteria for recognizing information, for distinguishing information from noise ... Indeed, they even dictate how such a framework is constructed by the questing infant in the first place" ("The Ontological Status of Observables," Images of Science, page 42). Thus, he concludes that since even our beliefs about what is observable are grounded in what van Fraassen calls the merely "pragmatic" virtues (so-called because they give us reason to use a theory without giving us reason to believe that it is true), then it cannot be unreasonable to use criteria such as simplicity, explanatory power, and coherence to form beliefs about what is unobservable to us. Van Fraassen's distinction between 'empirical, and therefore truth-relevant' and 'pragmatic, and therefore not truth-relevant' is therefore not a tenable one.

Churchland concludes with a consideration that I will leave you as food for thought. Suppose that a humanoid race of beings were born with electron microscopes for eyes. Van Fraassen would then argue that since for them the microstructure of the world would be seen directly, they would unlike us have different bounds on what they regard as "observable." Churchland regards this distinction as wholly unmotivated. He points out that van Fraassen's view leads to the absurd conclusion that they can believe in what their eyes tell them but we cannot, even though if we put our eyes up to an electron microscope we will have the same visual experiences as the humanoids. There is no differences between the causal chain leading from the objects that are perceived and the experience of perception in both cases, but van Fraassen's view leads to the conclusion that nevertheless we and the humanoids must embrace radically different attitudes towards the same scientific theories. This he regards as implausible.