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Instrumentalism is an interpretation within the philosophy of science that a successful scientific theory reveals nothing known either true or false about nature's unobservable aspects. By instrumentalism, then, scientific theory is a tool whereby humans predict observations in a particular domain of nature by organizing laws, which state regularities, but theories do not unveil hidden aspects of nature to explain the laws. Initially a novel perspective introduced by Pierre Duhem in 1906, instrumentalism is largely the prevailing practice of physicists today.
Rejecting scientific realism's ambitions to attain metaphysical truth about nature, instrumentalism is usually categorized as an antirealism, although its mere lack of commitment to scientific theory's realism can be termed nonrealism. Instrumentalism merely bypasses debate such as whether a particle talked about in particle physics is a discrete entity of individual existence, or is an excitation mode of a region of a field, or is something else altogether. Instrumentalism holds that theoretical terms need only be useful to predict the phenomena, the observed outcomes.
Until Thomas Kuhn's 1962 thesis, the prevailing views on science were roughly two. The populist was scientific realism, usually belief that science has progressively unveiled a truer view and built a better understanding of nature. The professional was logical empiricism, whereby a scientific theory is a logical structure whose terms all ultimately refer to observations, while an objective process neutrally arbiters theory choice, compelling true scientists to see and accept which scientific theory is better. Physicists knew better, but, busy developing the Standard Model, were so steeped in QFT—quantum field theory—that their talk, largely metaphorical, perhaps even metaphysical, was unintelligible to the public, while the mathematics, variously sloppy and steep, warded off even philosophers of physics. By the 1980s, physicists regarded not particles but fields as more fundamental, and no longer even hoped to discover what entities and processes might be nature's truly fundamental, perhaps not even a field. Kuhn had not claimed to present a novel thesis, but instead to usefully synthesis recent developments in philosophy of science.
In 1906, Duhem had introduced problem of underdetermination of theory by data, as any dataset can host over one explanation, how the success of any prediction does not, by affirming the consequent, a deductive fallacy, logically reveal the truth of the theory that the prediction was derived from. In the 1930s, Ludwik Fleck had explained the role of perspectivism in science whereby scientists are trained in thought collectives to adopt particular thought styles setting expectations for a proper scientific question, scientific experiment, and scientific data. Scientists tweak experimental conditions to get results that cohere with their own expectations—what the scientists presuppose is realistic—and invoke the experimenter's regress to rejected unexpected results, and then redo experiments under supposedly better and more ideal conditions. By the 1960s, physicists recognized two, differing roles of physical theory, formalism and interpretation. Formalism was mathematical equations and axioms that, upon input of physical data, were operated to yield predictions. Interpretation sought to explain why they succeed. Yet a motto prevailing in physics had become Just shut up and calculate.
Widely read, Kuhn's 1962 thesis seemingly shattered logical empiricism, whose paradigmatic science was physics and which espoused instrumentalism. Yet scientific realism, far more tenacious, then flared and attacked Kuhn's thesis, perennially depicted thereafter as either illuminated or infamous. Kuhn later indicated that his thesis had been so widely misunderstood that he himself was not a Kuhnian. With logical empiricism's fall, Karl Popper's falsificationism ascended, and Popper was knighted in 1965. Yet in 1961, the molecular biology research program had made its first major empirical breakthrough in cracking a genetic code. By the 1970s, molecular genetics' research tools could also be used for genetic engineering. In 1975, philosopher of science Hilary Putnam famously reasserted scientific realism by unveiling the no miracles argument—utterly simple—whereby the best scientific theories' predictive successes appear miraculous if the theories are not at least approximately true about reality as it exists in and of itself beyond human perception. Antirealist arguments arose in response.
Newton's theory of motion whereby any object instantly interacts with all other objects across the universe motivated the founder of British empiricism, John Locke, to speculate that matter can think. The next prime British empiricist, George Berkeley, argued that an object's putative primary qualities as recognized by scientists, such as shape, extension, and impenetrability, are inconceivable without the putative secondary qualities of color, hardness, warmth, and so on, why object can even be properly conceived to exist apart from its perception as sensations mental. Berkeley did not quibble with people's everyday talk about the reality of objects, but instead with philosophers talk as if they knew something, beyond sensory impressions, everyday folks did not.
For Berkeley, a scientific theory does not state causes or explanations, but simply identifies perceived types of objects and traces their typical regularities. Berkeley thus anticipated the basis of what Auguste Comte in the 1830s promulgated as positivism, although Comtean positivism added other principles as to the scope, method, and uses of science that Berkeley would have disavowed. Berkeley also noted the usefulness of scientific theory having terms that simply aid calculations without referring to anything in particular, so long as they ultimately directed one's action usefully. Berkeley thus predated the insight that logical positivists, who arose in the late 1920s, yet by the 1950s had softened into logical empiricists, would be compelled to accept: theoretical terms in science do not always translate into observational terms.
The last great British empiricist, David Hume, posed a number of challenges to Bacon's inductivism, which had been prevailing at least professed view of how to attain scientific realism. Though enjoying the scandal wrought by his philosophical skepticism, Hume found own criticisms—principally Hume's fork, the problem of induction, and Hume's law—ultimately insignificant except to show his inquiry into the human mind's machinations to be as worthy as physics. Regarding himself having placed his own theory of knowledge on par with Newton's theory of motion, Hume supposed that he had improved inductivism toward scientific realism. Upon reading Hume's work, Immanuel Kant was "awakened from dogmatic slumber", and quested to preempt any threat to science posed by Humean empiricism. Kant would develop the first stark philosophy of physics.
Idealism and positivism
To save Newton's law of universal gravitation, Kant reasoned that the mind is the precondition of experience and so, as the bridge from the noumena, which are how the world's things exist in themselves, to the phenomena, which are humans' recognized experiences. And so mind itself contains the structure that determines space, time, and substance, how mind's own categorization of noumena renders space Euclidean, time constant, and objects' motions exhibiting the very determinism predicted by Newtonian. Kant apparently presumed that the human mind, rather than a phenomenon itself that had evolved, had been predetermined and set forth upon the creation of humankind. In any event, the mind also was the veil of appearance that scientific methods could never lift. And yet the mind could ponder itself and discover such truths. Kant's metaphysics, then, transcendental idealism, secured science from doubt, and yet discarded hope of scientific realism. Meanwhile, it was a watershed for idealist metaphysics, and launched German idealism, most influentially Hegel's absolute idealism or objective idealism, or at least interpretations, often misinterpretations, and political misuses, of it.
According the mind virtually no power to know anything beyond direct sensory experience, Ernst Mach's positivism verged on idealism. It was alleged to even be a surreptitious solipsism, whereby all that exists is one's own mind. Mach's positivism also strongly asserted the ultimate unity of the empirical sciences. Mach's positivism asserted phenomenalism as to new basis of scientific theory, all scientific terms to refer to either actual or potential sensations, thus eliminating hypotheses while permitting such seemingly disparate scientific theories as physical and psychological to share terms and forms. Phenomenalism was insuperably difficult to implement, yet heavily influenced a new generation of philosophers of science, who emerged in the 1920s while terming themselves logical positivists while pursuing a program termed verificationism. Logical positivists aimed not to instruct or restrict scientists, but to enlighten and structure philosophical discourse to render scientific philosophy that would verify philosophical statements as well as scientific theories, and align all human knowledge into a scientific worldview, freeing humankind from so many of its problems due to confused or unclear language.
The verificationists expected a strict gap between theory versus observation, mirrored by a theory's theoretical terms versus to observational terms. Believing a theory's posited unobservables to always correspond to observations, the verificationists viewed a scientific theory's theoretical terms, such as electron, as metaphorical or elliptical at observations, such as white streak in cloud chamber. They believed that scientific terms lacked meanings unto themselves, but acquired meanings from the logical structure that was the entire theory that in turn matched patterns of experience. So by translating theoretical terms into observational terms and then decoding the theory's mathematical/logical structure, one could check whether the statement indeed matched patterns of experience, and thereby verify the scientific theory false or true. Such verification would be possible, as never before in science, since translation of theoretical terms into observational terms would make the scientific theory purely empirical, none metaphysical. Yet the logical positivists ran into insuperable difficulties. Schlick debated with Neurath over foundationalism—the traditional view traced to Descartes as founder of modern Western philosophy—whereupon only nonfoundationalism was found tenable. Science, then, could not find a secure foundation of indubitable truth.
And since science aims to reveal not private but public truths, verificationists switched from phenomenalism to physicalism, whereby scientific theory refers to objects observable in space and at least in principle already recognizable by physicists. Finding strict empiricism untenable, verificationism underwent "liberalization of empiricism". Carnap even suggested that empiricism's basis was pragmatic. Recognizing that verification—proving a theory false or true—was unattainable, they discarded that demand and focused on confirmation theory. Carnap sought simply to quantify a universal law's degree of confirmation—its probable truth—but, despite his great mathematical and logical skill, discovered equations never operable to yield over zero degree of confirmation. Hempel found the paradox of confirmation. By the 1950s, the verificationists had established philosophy of science as subdiscipline within academia's philosophy departments. By 1962, verificationists had asked and endeavored to answer seemingly all the great questions about scientific theory. Their discoveries showed that the idealized scientific worldview was naively mistaken. By then the leader of the legendary venture, Hempel raised the white flag that signaled verificationism's demise. Suddenly striking Western society, then, was Kuhn's landmark thesis, introduced by none other than Carnap, verificationism's greatest firebrand. Instrumentalism exhibited by scientists often does not even discern unobservable from observable entities.
By rejecting all variants of positivism via its focus on sensations rather than realism, Karl Popper asserted commitment to scientific realism, merely via the necessary uncertainty of his own falsificationism. Popper alleged that instrumentalism reduces basic science to merely applied science.
Torretti, Roberto, The Philosophy of Physics (Cambridge: Cambridge University Press, 1999), Berkeley pp 98, 101-04.
- Anjan Chakravartty, "Scientific realism", §4 "Antirealism: Foils for scientific realism: §4.1: "Empiricism", in Edward N Zalta, ed, The Stanford Encyclopedia of Philosophy, Summer 2013 edn: "Traditionally, instrumentalists maintain that terms for unobservables, by themselves, have no meaning; construed literally, statements involving them are not even candidates for truth or falsity. The most influential advocates of instrumentalism were the logical empiricists (or logical positivists), including Carnap and Hempel, famously associated with the Vienna Circle group of philosophers and scientists as well as important contributors elsewhere. In order to rationalize the ubiquitous use of terms which might otherwise be taken to refer to unobservables in scientific discourse, they adopted a non-literal semantics according to which these terms acquire meaning by being associated with terms for observables (for example, 'electron' might mean 'white streak in a cloud chamber'), or with demonstrable laboratory procedures (a view called 'operationalism'). Insuperable difficulties with this semantics led ultimately (in large measure) to the demise of logical empiricism and the growth of realism. The contrast here is not merely in semantics and epistemology: a number of logical empiricists also held the neo-Kantian view that ontological questions 'external' to the frameworks for knowledge represented by theories are also meaningless (the choice of a framework is made solely on pragmatic grounds), thereby rejecting the metaphysical dimension of realism (as in Carnap 1950)".
- Samir Okasha, Philosophy of Science: A Very Short Introduction (New York: Oxford University Press, 2002), p 62: "Strictly we should distinguish two sorts of anti-realism. According to the first sort, talk of unobservable entities is not to be understood literally at all. So when a scientist pus forward a theory about electrons, for example, we should not take him to be asserting the existence of entities called 'electrons'. Rather, his talk of electrons is metaphorical. This form of anti-realism was popular in the first half of the 20th century, but few people advocate it today. It was motivated largely by a doctrine in the philosophy of language, according to which it is not possible to make meaningful assertions about things that cannot in principle be observed, a doctrine that few contemporary philosophers accept. The second sort of anti-realism accepts that talk of unobservable entities should be taken at face value: if a theory says that electrons are negatively charged, it is true if electrons do exist and are negatively charged, but false otherwise. But we will never know which, says the anti-realist. So the correct attitude towards the claims that scientists make about unobservable reality is one of total agnosticism. They are either true or false, but we are incapable of finding out which. Most modern anti-realism is of this second sort".
- Roberto Torretti, The Philosophy of Physics (Cambridge: Cambridge University Press, 1999), pp 242–43: "Like Whewell and Mach, Duhem was a practicing scientist who devoted an important part of his adult life to the history and philosophy of physics. ... His philosophy is contained in La théorie physique: son objet, sa structure [The Aim and Structure of Physical Theory] (1906), which may well be, to this day, the best overall book on the subject. Its main theses, although quite novel when first put forward, have in the meantime become commonplace, so I shall review them summarily without detailed argument, just to associate them with his name. But first I ought to say that neither in the first nor in the second (1914) edition of his book did Duhem take into account—or even so much as mention—the deep changes that were then taking place in physics. Still, the subsequent success and current entrenchment of Duhem's ideas are due above all to their remarkable agreement with—and the light they throw on—the practice of mathematical physics in the twentieth century. In the first part of La théorie physique, Duhem contrasts two opinions concerning the aim of physical theory. For some authors, it ought to furnish 'the explanation of a set of experimentally established laws', while for others it is 'an abstract system whose aim is to summarize and logically classify a set of experimental laws, without pretending to explain these laws' (Duhem 1914, p 3). Duhem resolutely sides with the latter. His rejection of the former rests on his understanding of 'explanation' ('explication' in French), which he expresses as follows: 'To explain, explicare, is to divest reality from the appearances which enfold it like veils, in order to see the reality face to face' (pp 3–4). Authors in the first group expect from physics the true vision of things-in-themselves that religious myth and philosophical speculation have hitherto been unable to supply. Their explanation makes no sense unless (i) there is, 'beneath the sense appearances revealed to us by our perceptions, [...] a reality different from these appearances' and (ii) we know 'the nature of the elements which constitute' that reality (p 7). Thus, physical theory cannot explain—in the stated sense—the laws established by experiment unless it depends on metaphysics and thus remains subject to the interminable disputes of metaphysicians. Worse still, the teachings of no metaphysical school are sufficiently detailed and precise to account for all of the elements of physical theory (p 18). Duhem instead assigns to physical theories a more modest but autonomous and readily attainable aim: 'A physical theory is not an explanation. It is a system of mathematical propositions, derived from a small number of principles, whose purpose is to represent a set of experimental laws as imply, as completely, and as exactly as possible (Duhem 1914, p 24)".
- P Kyle Stanford, Exceeding Our Grasp: Science, History, and the Problem of Unconceived Alternatives (New York: Oxford University Press, 2006), p 198.
- Roberto Torretti, The Philosophy of Physics (Cambridge: Cambridge University Press, 1999), pp 396-97, including quote: "First, quantum field theories have been the working theories at the frontline of physics for over 30 years. Second, these theories appear to do away with the familiar conception of physical systems as aggregates of substantive individual particles. This conception was already undermined by Bose–Einstein and Fermi–Dirac statistics (§6.1.4), and greatly impaired by QM, according to which the so-called particles cannot be assigned a definite trajectory in ordinary space. But quantum field theories go a long step further and—or so it would seem—conceive 'particles' as excitation modes of the field. This, I presume, motivated Howard Stein's saying that 'the quantum theory of fields is the contemporary locus of metaphysical research' (1970, p 285). Finally, the very fact that physicists conspicuously and fruitfully resort to unperspicacious theories can teach us something about the aim and reach of science. Here is how physicists work, dirty-handed, in their everyday practice, a far cry from what is taught at the Sunday school of the 'scientific worldview' ".
- Meinard Kuhlmann, "Physicists debate whether the world is made of particles or fields—or something else entirely, Scientific American, 2013 Aug;309(2).
- Torretti 1999 p 75.
- Torretti 1999 p 101–02.
- Torretti 1999 p 102.
- Torretti 1999 p 103.
- Torretti 1999 p 98: "I shall dwell at some length on Kant's conception of the sources and scope of Newton's conceptual frame, for it was the first full-blown philosophy of physics and remains to this day the most significant".
- Karl R Popper, Conjectures and Refutations: The Growth of Scientific Knowledge, (London: Routledge, 2003), ISBN 0-415-28594-1, quote: "Instrumentalism can be formulated as the thesis that scientific theories—the theories of the so-called 'pure' sciences—are nothing but computational rules (or inference rules); of the same character, fundamentally, as the computation rules of the so-called 'applied' sciences. (One might even formulate it as the thesis that "pure" science is a misnomer, and that all science is 'applied'.) Now my reply to instrumentalism consists in showing that there are profound differences between "pure" theories and technological computation rules, and that instrumentalism can give a perfect description of these rules but is quite unable to account for the difference between them and the theories".