Question:1. Explain (a) or (b) using between 200 and 300 words. Give as much detail as you can, including the relevant backgr
1. Explain (a) or (b) using between 200 and 300 words. Give as much detail as you can, including the relevant background knowledge. a. The Original Indispensability Argument and its problems b. The Enhanced Indispensability Argument and its problems 2. Explain (a) using between 200 and 350 words. Give as much detail as you can, including the relevant background knowledge. a. Reintroduction 3. Explain (c) using between 200 and 300 words. Give as much detail as you can, including the relevant background knowledge. c. Constructive empiricism 4. 1. Answer (a) or (b) using between 200 and 300 words. Give as much detail as you can, including the relevant background knowledge. a. How do mathematical models represent the world? b. Why is the applicability of mathematics in science important to the mathematical realism debate?
3. Van Fraassen’s constructive empiricism
Van Fraassen’s constructive empiricism is one of the most discussed current alternatives to scientific realism. Contrary to positivists, Van Fraassen does believe that scientific theories must be taken literally. In that sense, he rejects the positivist reinterpretations of scientific statements, according to which talk of unobservablesis only a convenient abbreviation of complicated talk about observables. For the positivists, in principle,everything scientists say about unobservable reality can be expressed, without any kind of loss whatsoever, into statements referring only to observables. But Van Fraassen disagrees. He thinks that scientific statements regarding unobservables are meaningful. If a theory says that ‘electrons are not planets’ then the theory is asserting the existence of both electrons and planets. And if the theory happens to be true, both electrons and planets would exist. But here is the twist in Van Fraassen’s story. According to him, “there is no need to believe good theories to be true, nor to believe ipso facto that the entities they postulate are real” (1065). He defines Constructive Empiricism like this:
“Science aims to give us theories which are empirically adequate; and acceptance of a theory involves a beliefonly that it isempirically adequate” (1065)
A theory is empirically adequate “if what it says about the observable things and eventsin the world is true –exactly if it ‘saves the phenomena’” (1065). Contrast this with what he takes to be the correct definition of Scientific Realism:
“Science aims to give us, in its theories, a literally true story of what the world is like; and acceptance of a scientific theory involves the belief that it is true” (1062)
The first thing to note is that both definitions focus on the aims of science, and not on its actual accomplishments. According to the constructive empiricist picture, science does posit unobservables, but its aim is only to be correct about its observational claims. Against this, the scientific realist picture says that the aim of science is to be actually correct in their claims about unobservables. By focusing merely on the aims of science, Van Fraassen in a way lowers the stakes of this debate. It is no longer about whether or not current scientific theories are correct regarding the unobservable part of the world, but about what is supposed to be the main goal of these theories. Now, whether or not this is a good way of framing the debate is debatable. Most realistsbelieve, I think, that science gets at least part of the unobservable world right. (Van Fraassen’s reply, as we saw in week 6, is that there is no noncircular way to verify the truth of claims about unobservables. But as we saw, the same happens with claims regarding observables!)
Now, something can be observable and yet unobserved. ‘Stones are hard’ aims to be true about both observed stonesand those that haven’t been. That statement, however, is not about ‘unobservables’, in the sense of objects that cannot be observed in principle by any human. ‘Stones are hard’ refers to the observable object stone and the observable property of being hard. It’s not about observations made at one point in time. Accepting a theory means accepting what it says about the observable part of the world, past, present, and future. Observable, on Van Fraassen’s view, is what we get in unaided acts of perception (1067).
“The human organism” says Van Fraassen, “is, from the point of view of physics, a certain kind of measuring apparatus. As such, it has certain inherent limitations… It is these limitations to which the ‘able’ in ‘observable’ refers—our limitations, qua human beings” (1070).
But with respect to the unobservable reality, an accepted theory may as well be false. It really doesn’t matter for the understanding of science. In that sense, constructive empiricism advocates agnosticism regarding the theory’s claims about the unobservable reality.
In terms of our discussion regarding scientific inference, we can say that Van Fraassen accepts ‘horizontal inferences’, or if you want ‘inferences that remain at the surface’, that is, inductive inferences from observable cases to observable cases. But he doesn’t accept ‘vertical inferences’, ‘inferences that go deeper than the surface’, that is, abductive inferences which conclusions refer to the unobservable causes of the phenomena.
Many realists have contested this distinctionas arbitrary. Why believingin induction, despite Hume, but not believing in abduction? There are many things that are unobserved but observable in Van Fraassen’s lights, like the core of the Earth, but it seems that our understanding of it is purely theoretical and also based on abductive inferences. There’s no reason to reject these inferences in those cases, but then if that’s true there wouldn’t be any reason to rejecting these inferences in other cases as well. The laws of nature go well beyond evidence, just like abduction does. Why would we prefer one over the other is not clear, despite Van Fraassen’s argument.
One important pragmatic aspect of Van Fraassen’s view, is that although accepting a theory only means accepting that the theory is empirically adequate, one can still use the whole machinery the theory puts at one’s disposal, which includes the unobservable structures and processes. Van Fraassen is not advocating for a change in the practice of science. His point is rather that if the theory works and accommodates past, present and future empirical evidence, then we don’t need to worry about whether the theory is true. ‘Why is the theory so successful?’ is not an interesting question. Perhaps this theory is successful because all other unsuccessful theories died out and were abandoned (this is a kind of ‘survival of the fittest’ argument). The reason our theories are successful is that we reject those that aren’t. A meta-scientific explanation regarding why they are successful is out of order, on Van Fraassen’s view. This has been contested by many philosophers who think that explaining the success of scienceis one of the most interesting tasks of philosophy of science, and there’s no reason to abandon it.
A final remark with respect to Van Fraassen’s criticism of the overlap argument. We saw that the overlap argument proposes some sort of instrument calibration. For example, we can verify the magnification powers of a microscope by applying it to observable objects first. Once we do that, there is no reason not to trust it when applied to things that would be unobservable to the naked eye, like proteins. Van Fraassen’s reliance on human capacities of observation seems arbitrary, because if we accept what we see through our spectacles, there’s no in-principle reason not to accept what we see through a microscope. Against this, Van Fraassen says that that is debatable, because the term observable is just vague, but there are clear cases of unobservableentities, like so-called unobservables in principle, and the overlap argument does not extend to them. As I mentioned before, it doesn’t seem that the overlap argument itself can deal with this objection, which doesn’t mean that antirealism wins, because as we will see, there are many more arguments defending this view.
,
McMullin’s Inference: A Case for Realism? with Bas C. van Fraassen, “Scientific Realism and the Empiricist Challenge: An Introduction to Ernan McMullin’s Aquinas Lecture”; and Ernan McMullin, “The Inference that Makes Science”
THE INFERENCE THAT MAKES SCIENCE
by Ernan McMullin
Abstract. In his Aquinas Lecture 1992 at Marquette University, Ernan McMullin discusses whether there is a pattern of inference that particularly characterizes the sciences of nature. He pursues this theme both on a historical and a systematic level. There is a continuity of concern across the ages that separate the Greek inquiry into nature from our own vastly more complex scientific enterprise. But there is also discontinuity, the abandonment of earlier ideals as unworkable. The natural sciences involve many types of inference; three of these interlock in a special way to produce “retroductive inference,” the kind of complex inference that supports causal theory.
Keywords: abduction; Thomas Aquinas; Aristotle; causality; demonstration; Galileo Galilei; inference; realism; science; theory
Is there a pattern of inference that particularly characterizes the sciences of nature? Theorists of science, from Aristotle’s day to our own, have on the whole tended to answer in the affirmative, though views have changed as to what that pattern is. It has usually been linked, in one way or another, with explanation. To demonstrate in proper scientific form, Aristotle noted, is also to explain. The credibility of a theoretical inference, it might be said today, is proportionate to its explanatory success.
My aim in this essay is to pursue this theme, the nature of the inference that constitutes a claim as “science,” both on a historical and a systematic level. As historians, we shall find a continuity of concern, a link across the ages that separate the Greek inquiry into nature from our own vastly more complex scientific enterprise. But we shall also discover discontinuity, the
Ernan McMullin (1924–2011) held the John Cardinal O’Hara Chair of Philosophy, and was director of the program in history and philosophy of science at the University of Notre Dame, South Bend, IN, USA. The text is reproduced from Ernan McMullin, The Inference that Makes Science (Milwaukee: Marquette University Press, 1992, 1–112). Beginnings of pages in the original are indicated with the page number between / and /. C© Marquette University Press, 1992. Reprinted with permission.
[Zygon, vol. 48, no. 1 (March 2013)] C© 2013 by the Joint Publication Board of Zygon ISSN 0591-2385 www.zygonjournal.org
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abandonment of earlier ideals as unworkable. Indeed, it is arguable that the failure (in its own terms) of Aristotelian natural philosophy may to some degree have been linked with its emphasis on demonstration, on a science of nature that would rest on causal claims held to be evident in their own right. We shall find /2/ a worry among medieval Aristotelians that a demonstrative science of nature might be very difficult of achievement or might even be out of reach. The deep shift that we have come to call the “Scientific Revolution” can be regarded as in large part an attempt to construct an alternative to demonstration, a “New Organon,” as its most influential protagonist dubbed it. We shall discover that the New Organon was fundamentally ambiguous, that it involved two quite different patterns of inference. It took more than two centuries before this was finally recognized. And even in our own century, it was implicitly denied, first by the logical positivists, and more recently by those who, for whatever reason, reject scientific realism. Since our canvas is such a large one, we shall have to be content with broad strokes. Besides Aristotle, there will be a host of other characters: Grosseteste, Zabarella, Bacon, Whewell, Peirce . . . . And Aquinas, needless to say, will not be forgotten.
We shall come to see that the natural sciences involve many types of inference-pattern; three of these interlock in a special way to produce what we shall call retroductive inference, the kind of complex inference that supports causal theory. Since theories are primarily designed to explain, explanatory power obviously plays a major part in their warranting. But there is a good deal /3/ of disagreement about how this warranting role may best be understood. We shall, for example, challenge the thesis often associated with the hypothetico-deductive (H-D) account of scientific knowledge which would limit the warrant of a theory to the sum of the verified consequences deductively derivable from it.
It may be worth noting from the beginning that the attempt to define “the inference that makes science” is not intended to furnish a criterion of demarcation between science and nonscience. The issue of demarcation has been actively debated ever since Popper made it central to his philosophy of science. We shall not address it here. Suffice it to say that retroductive inference makes use of ingredients that are commonplace in human reasoning generally. One finds them in any inquiry into causes, in the work of a detective or a newspaper reporter, for example. What is distinctive about the way in which explanatory theories are constructed and tested in natural science is the precision, as well as the explicitness, with which retroductive inference is deployed. But this alone is not enough to enable a sharp boundary line to be drawn. There will be large areas where a clear cut decision will not be possible, where, for example, the questions: “good science or bad science?” and “science or non-science?” will inevitably overlap. /4/
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The sciences of human behavior pose a further, and equally debatable, question. Is the pattern of inference that constitutes these as “science” the same as (or, at least, very similar to) that employed by the natural sciences? Do they explain in more or less the sense in which, say, chemistry explains? Do they work back from observed effects to underlying structural causes as chemical theories do? Once again, we shall have to set aside an important issue in order to focus on the already-large one at hand. Our concern here is with the natural sciences, and with a single question: in what kind of complex inference do they (ideally) culminate? Of course, this limitation would have been foreign to the intentions of Aristotle, from whose seminal work on the theory of science, the Posterior Analytics, our inquiry takes its start. His aim was to discover what the ideal of knowledge (episteme) should be, while warning against seeking a greater degree of precision in any domain than the nature of the inquiry admits.
PART ONE: DEMONSTRATION ALONE
Aristotle on Demonstration. What makes knowledge “scientific” (epistemonikos) according to Aristotle is that it should constitute strict demonstration (apodeixis). And by demonstration /5/ he means an inference from premisses which are true, primary, immediate, more knowable (gnorimos) than, and prior to the conclusion, and further that the premisses furnish an explanation of the conclusion.1 It is not enough that the inference be a deductively valid syllogism; logical validity does not suffice to render a piece of reasoning scientific. It is not even enough that the inference be a valid one from true premisses. The premisses must be of a quite definite kind, and they must specify in a unique way the cause of the effect or property of which scientific knowledge is desired.
How are the premisses of the requisite sort to be obtained? Not by further demonstration, for that would lead to regress. The premisses must be primary and immediate; that is, they must carry conviction in their own right once they are properly understood. (The English term “self-evident,” with its overtone of “obvious,” can be misleading in this context.) But how is such an understanding to be attained? Aristotle knew perfectly well that on an answer to this question his entire account of science would stand or fall. But he is famously laconic in his response.2
Experience (empeiria) is, it appears, crucial to the discovery of the necessary premisses, the starting points of demonstration in natural science: /6/
It pertains to experience to provide the principles of any subject. In astronomy, for example, astronomical experience supplied the principles of the science; it was only when the phenomena were adequately grasped that the demonstrations proper to astronomy were discovered. Similarly with any other art or science.3
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Through perception we register particulars, but these particulars themselves are not objects of scientific knowledge, which is directed to universals.4 The process leading from the perception of particular things to the grasp of universals Aristotle calls epagoge, which is often translated as “induction.” Is there, then, a second sort of inference, a form of systematic generalization, that provides the starting point for demonstration? Ought we say that Aristotle proposes not one but two forms of inference, demonstration and induction, together leading to science (episteme)? Epagoge is, indeed, sometimes described as though it proceeded by enumeration, or depended on a systematic comparison of instances.5
But any resemblance to what Bacon will later call induction is misleading. In Aristotle’s view, it seems, rather, to be a process of recognizing the universal in a few particulars, of grasping the phenomena as instances of a specific universal. It does not depend on sample size.6 There is first the /7/ ability to perceive (which humans share with animals); the perceptions persist and constitute memory. And “out of frequently repeated memories of the same thing develops experience.”7 In this way the universal is, as it were, “stabilized” in the soul, bringing about a state of mind called nous (insight, intuition, comprehension). Nous is a direct grasp of the universals already implicit in perception, and is brought about by epagoge.8 It is more basic than demonstration; it is, Aristotle assures us, the originative source of science since it anchors the premisses from which demonstration begins.9
Underlying this analysis, of course, is Aristotle’s doctrine of the mind’s ability to receive the form of an object. “The thinking part of the soul must therefore be, while impassible, capable of receiving the form of an object; that is, it must be potentially identical in character with its object without being the object.”10 So that “mind is what it is in virtue of becoming all things.”11 The veridical character of episteme depends on this ability of mind to grasp form, as presented in perceived appearance. The form conveys the essential nature of the thing perceived, and so the basic premisses of demonstration can be required not only to be true but to be necessarily true, displaying causal relationships that are “more knowable” in themselves than the fact to be demonstrated. /8/
Here in brief and familiar outline is how Aristotle proposes that science should be acquired. There are obviously many difficulties and obscurities in the account. How, for example, is one to deal with the obvious problem of sense-error? Aristotle himself points it out: “We must maintain that not everything which appears is true; firstly, because even if sensation . . . is not false, still appearance is not the same as sensation.”12 Only “reliable” (aei kurios) phenomena can serve as a basis for natural science, he reminds his reader.13 But how is one to know, in an absolutely assured way, which of the phenomena can be counted as reliable?
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More fundamentally, what justifies us in supposing that the forms given us in perception really do convey the essence of the thing perceived? Aristotle recognizes in passing that there may be a “failure” in perception when we are unable to perceive the inner structures of a substance on which a property, like the ability of a burning-glass to set objects on fire, may depend.14 If we were to be able to see pores in the glass and the light passing through these pores, then “the reason of the kindling would be clear to us.” But as it is, such microstructures lie permanently outside the range of our senses. “Light shines through a lantern because that which consists of relatively small particles necessarily passes through pores /9/ larger than those particles.”15 Aristotle is clearly aware of the challenge this sort of explanation poses for his phenomenalist account of the natural sciences, but he nowhere deals with this directly.16 Instead, he restricts himself to observed correlations in the examples on which he relies (as in his celebrated explanation of the lack of incisors in the upper jaws of horned animals in terms of the nutriment needed for their horns17), or to simple causal analyses, as in his frequent references to eclipses.
In a significant passage, he draws a distinction between knowledge “of the fact” (oti, quia) and knowledge “of the reasoned fact” (dioti, propter quid ). Since he is trying in this passage to explain how demonstration works, the examples he chooses are of special interest. They are drawn from astronomy, an odd choice it might seem. Our perceptual knowledge of the heavenly bodies is obviously very limited; they are, he notes elsewhere:
excellent beyond compare and divine, but less accessible to knowledge. The evidence that might throw light on them, and on the problems we long to solve respecting them, is furnished but scantily by sensation. Whereas respecting perishable plants and animals we have abundant information, living as we do in their midst. Both domains, /10/ however, have their special charm. The scanty conceptions to which we can attain of celestial things give us, from their excellence, more pleasure then all our knowledge of the world in which we live . . . . On the other hand, in certitude and completeness our knowledge of terrestrial things has the advantage. Moreover, their greater nearness and affinity to us balances somewhat the loftier interest of the heavenly things . . . .18
Where the presumptive pores in glass that allow light to pass are imperceptible to us because of their minute size, the difficulty with the heavenly bodies is one both of distance and of nature. Not only does their great distance prevent us from observing their properties in any other than a perfunctory way, but (in Aristotle’s view, at least) we have reason to believe that these bodies are fundamentally different in nature to the bodies of earth by means of which our perceptual expectations have been molded. So our explorations of the skies must be regarded as conjectural. Why, then, choose examples drawn from astronomy to illustrate a thesis about strict demonstration in natural science? Was it just because of his general fondness for astronomical illustrations (“a half-glimpse of persons
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that we love is more delightful than a more leisurely look at others”19), or was it /11/ because these examples were in some special way apposite?
The Nontwinkling Planets. The distinction he draws between two grades of knowledge was intended in part to help overcome the difficulty of discovering a unique causal explanation when one has to work backward from perceived effect to less familiar cause. To see this will require a detailed analysis of the key passage in the Posterior Analytics (I, 13). He gives two examples of the sort of problem that, despite appearances, lends itself to demonstration. The most striking property of the planets (other than the “wandering” motion that gave them their original Greek name) is that they do not twinkle. Alone among the heavenly bodies they shine with a steady light. How are we to explain this? How are we to “demonstrate” the property of nontwinkling they possess? Only by finding the more basic property of planets responsible for the fact that they do not twinkle. Aristotle proposes nearness as a plausible candidate. But are the planets nearer than the other heavenly bodies? A confident assertion follows: “That which does not twinkle is near: we must take this truth as having been reached by induction or sense-perception.”20 /12/
This gives him an apparent proof of nearness:
S1 A That which does not twinkle is near B The planets do not twinkle
Therefore the planets are near
This he calls a demonstration of the fact (oti). It is an improper demonstration because it is not causally explanatory: nontwinkling does not explain the nearness. The major premiss is merely an observed correlation between two properties of shining bodies: if they do not twinkle, then they are observed to be near. This is sufficient, however, to prove the truth of the conclusion. And now this conclusion can become the minor premiss of a new syllogism:
S2 A Nearby (shining) objects do not twinkle B Planets are near
Therefore planets do not twinkle
This is (Aristotle says) a demonstration of the reasoned fact, a proper demonstration, because it gives the cause of (or reason for) the fact. The middle term joining the extremes functions to explain the link between them: nearness is the reason why planets do not twinkle. What gives this demonstration force as demonstration for Aristotle is not merely its syllogistic validity but its explanatory force. /13/
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But is S2 a proper demonstration? It would appear not, and for two separate reasons. Neither premiss seems to qualify as the sort of necessary truth that a demonstration requires as starting point. How would one establish the necessity of S2A, the claim that nearby shining objects do not twinkle? It is not enough that it just happens to be true (if indeed it is true). “True in every instance,” Aristotle himself reminds us, does not suffice; the attribute (nontwinkling, in this case) must be “commensurately universal,” that is, it must belong to every instance (of nearby shining object) essentially.21 It must be shown to “inhere necessarily in the subject.” Induction-as-generalization will not do; at best, all it can show is factual correlation of attribute and subject. Epagoge cannot (as Aristotle knows) reduce to induction, in the sense of generalization.
It is worth noting, indeed emphasizing, that exactly the same issue arose for the logical positivists when they tried to define the notion of “law” that was so basic to their account of explanation. It is not enough for an inductive generalization to be factually true (“everyone in this room is over five feet tall”) for it to serve as the starting point of a scientific explanation. An “accidental” universal will not sustain the sort of counterfactual conditional (“if x had been in this room . . . ”) that is taken to be diagnostic of “genu- /14/ ine” (what Aristotle would call “essential”) lawlikeness. We shall return to this later. Suffice for the moment to say that any account of science that rests (as Aristotle’s does) on attributes given in perception is bound to have trouble in separating “essential” from accidental linkages, in construing causality as anything more than invariable correlation.
How is epagoge supposed to lead us to the insight that nearness is the cause of nontwinkling in the planets? Is some kind of immediate grasp of the universals, nearness and nontwinkling (in the case of planets), sufficient? It is clearly not enough for epagoge to bring us to recognize the two universals in their particular instances; they have also to be seen as causally (necessarily) related. In On the Heavens, Aristotle does give a hint as to what the causal relationship might be. Noting that the sun appears to twinkle at sunrise and sunset, he goes on:
This appearance is due not to the sun itself but to the distance from which we observe it. The visual ray being excessively prolonged becomes weak and wavering. The same reason probably accounts for the apparent twinkling of the fixed stars and the absence of twinkling in the planets. The planets are near, so that the visual ray reaches them in full vigor, but when it /15/ comes to the fixed stars it is quivering because of the distance and its excessive extension; and its tremor produces an appearance of motion in the star.22
Here is a theoretical account of why twinkling occurs, and how it may be due to distance. It relies on the notion of a “visual ray” that goes out from the eye, and is attenuated by distance. This is obviously not something that could be derived directly by epagoge from perception of particulars. It is a tentative conjecture about an underlying process that might account
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for the twinkling of the distant stars. Its explanatory force comes from its ampliative character: it does not just associate twinkling with great distance, but suggests why this association might betoken a causal connection. The necessity is of a weak hypothetical sort: if there are visual rays and if visual rays tend to attenuate with distance (more theory needed here), then the stars will (necessarily) twinkle. What allows one to transcend mere factual correlation in this case is not nous as direct insight into essence, into causal relations themselves not given in perception, but plausible theoretical reconstruction in terms of postulated underlying structures.
In his “official” account of the nature of demonstration in natural science in the Posterior Analytics, Aristotle nowhere explicitly admits the /16/ mediating role played by theory in the establishing of causal connections. He leaves the reader to believe that there is a power of mind which can somehow, subsequent to perception, attain to the essence of natural things immediately. It is not hard to see why he does this. It is crucial, in his mind, that the premisses from which science begins be “primary,” that is, not themselves in need of further evidential support. They must be definitively true. Unless this be granted, there is no hope of attaining the “eternal and necessary knowledge” that he holds out as the aim of his inquiry into nature. But once one admits that either premiss is “theoretical” in the sense sketched above, one has implicitly given up on this aim. For theory (e.g., about visual rays) is clearly not primary; it is in need of further corroboration, of systematic testing. Nor is it definitive; Aristotle himself allows that his suggestion that visual rays attenuate in vigor the further they travel is at best only probable.
His attempt to supplement the phenomenalism of his starting point with an optimistic rationalist account of what epagoge can accomplish, brings out the main weakness in his account of demonstration. This can be seen in another way if we shift attention to the minor premiss, S2B. How are we to know that this premiss is true? Perception alone does not allow us to claim that the /17/ planets are near. Their nearness is not perceived; it has to be inferred. How, then, can the minor premiss be regarded as primary? Aristotle introduces a distinction between something “more knowable in itself’ and something “more knowable to us.”23 The fact that planets do not twinkle is more knowable to us; the fact that they are near is more knowable in itself because it serves as a causal princip
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