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Journal of Philosophy, Inc.

On the Stability of the Laboratory SciencesAuthor(s): Ian HackingSource: The Journal of Philosophy, Vol. 85, No. 10, Eighty-Fifth Annual Meeting AmericanPhilosophical Association, Eastern Division (Oct., 1988), pp. 507-514Published by: Journal of Philosophy, Inc.Stable URL: http://www.jstor.org/stable/2026809

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THE JOURNAL OF PHILOSOPHYVOLUME LXXXV, NO. 10, OCTOBER 1988

ON THE STABILITY OF THE LABORATORY SCIENCES*IS our knowledgeof natureunstable, constantlyyieldingto re-futation or revolution? You might think so, to judge by recentphilosophy. In this summary I propose a framework in which tounderstand the manifest fact that science since the seventeenth cen-tury has, by and large, been cumulative. The framework does notquestion the chief insights of Karl Popper or Thomas Kuhn, butplaces them in a larger perspective.My theme is the stability of "mature" laboratory sciences. It con-cerns only those sciences in which we investigate nature by the use ofapparatus in controlled environments, and are able to create phe-nomena that never or at best seldom occur in a pure state beforepeople have physically excluded all "irrelevant" factors. By labora-tory science I do not mean just the experimental side of a science. Mytopic is the stabilizing relationship between theory and experiment.STABILITYManymature sciences are pedagogically stable. We learn geometricaloptics when young, the wave theory as teenagers, Maxwell's equa-tions on entering college, some theory of the photon in seniorclasses, and quantum field theory in graduate school. Newton's raysof light particles are omitted, as are many other byways. Each ofthese stages is taught as if it were true. The sophisticated teachermay add, "but not really true." Each earlier stage is at best approxi-mately true.Some scientific realists embrace this (and an implied stability),holding that science converges on the truth. The implication is thatearlier stages are approximately true. Paul Feyerabend rejected the

* To be presented in an APA symposium on The Philosophical Significance ofExperimentation, December 28, 1988. Patrick Heelan will be co-symposiast, andPeter Galison will comment; see this JOURNAL, this issue, 515-524 and 525-527,respectively, for their contributions.0022-362X/88/8510/0507$00.80 ? 1988 The Journal of Philosophy, Inc.

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508 THE JOURNAL OF PHILOSOPHYapproximation idea on the grounds that successive stages are in-commensurable. Before Nancy Cartwright, few on either side exam-ined actual practices of approximation. One can argue that her mul-tiplicity of possible approximations both toward and away from thetruth suffices to show that all such considerations about approxima-tion are jejune.Here is a telling example due to S. S. Schweber. In 1981, workersat the University of Washington devised the Penning trap, whichcontains a single electron in a definite space. Everything they did wasplanned according to and can be explained by the prerelativistic(pre-Dirac) theory of the electron. It is not clear that it can be doneotherwise. For those purposes, that old account of the electron isbetter than any other; it is the account which is true to the facts: trueto the experiment and its applications.One suggestive idea about how stability arises relies on the obser-vation that theories and laboratory equipment evolve in such a waythat they match each other and are mutually self-vindicating. Suchsymbiosis is a contingent fact about people, our scientific organiza-tions, and nature. Another contingency is that new types of data canbe produced, thought of as resulting from instruments that probemore finely into microstructure, data which cannot be accommo-dated by established theory. This creates space for a mutual maturingof new theory and experiment, but does not necessarily dislodge anestablished mature theory, which remains true of the data availablein its domain. 'Data', 'theory', 'experiment', 'equipment'-these arefamiliar words, but, to expound this notion of stability, we require afiner taxonomy.ELEMENTS OF LABORATORY EXPERIMENTThanks to a large number of recent studies by philosophers, histo-rians, and ethnographers of experimental science, we have muchricher sources of material about the laboratory than was available adecade ago. The welter of colorful examples makes it hard to pro-duce any tidy formal characterization of experiment. Hence, ourpowers of generalization are limited. I shall try to return some de-gree of abstraction to the philosophy of science by listing some famil-iar elements in laboratory experimentation.

(1) There is a question or questions about some subject matter. (Aquestion answered at the end of the experiment may not even havebeen posed at its commencement; conversely, what prompted thework may disappear not only from the official write-up, but evenfrom living memory). Questions range from those rare ones empha-sized by philosophers ("Which of these two competing theories isfalse?") to the commonplace ("What is the value of this quantity?" or


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PHILOSOPHICAL SIGNIFICANCE OF EXPERIMENTATION 509"Does treating X with Y make a difference?"). When a question isabout a theory, I shall speak of the theory in question.

(2) Established or working theories or background bodies ofknowledge or assumptions about the subject matter. These are of atleast three kinds.(2a) Background knowledge and expectations which are not sys-tematized and which play little part in writing up an experiment.(2b) Theory of a general and typically high-level sort about thesubject matter, and which, by itself, may have no experimental con-sequences. Call this systematic theory.(2c) What in physics is commonly called phenomenology, whatR. B. Braithwaite called Campbellian hypotheses, and what manyothers call bridge principles. I shall speak of topical hypotheses.Hypothesis is used in the old-fashioned sense of something morereadily revised than theory. It is overly propositional. I intend it tocover whole sets of approximating procedures in the sense ofCartwright, and what Kuhn called the "articulation" of theory inorder to create a potential mesh with experience. That still ignores amore tacit dimension, the skills used by the "phenomenologist" to

create that articulation in practice. Topical is meant to connote boththe usual senses of 'current affairs' or 'local', and also to recall themedical sense of a topical ointment applied to the surface of the skin,i.e., not deep. Here are two extreme examples from physics: in thecase of a measurement of local gravitational acceleration (3 c below),the systematic theory is Galilean mechanics, and there is today noself-conscious "phenomenology," no formulated bridge principlesor topical hypotheses. In the case of superstring theory, a potentialgrand unified theory of many dimensions, topical hypotheses con-nect this structure with something that happens in our three or fourdimensional world.(3) There is the materiel of the experiment. Commonly thisbreaks down into three parts, each associated with a set of in-struments.(3a) There is a target that is prepared by some devices.(3b) There is apparatus that is used to interfere with the target insome way.(3c) There is a detector that determines some effects of the inter-ference.I arbitrarily restrict the word 'apparatus' to (b), and will use in-strument generically for (a-c). In elementary chemistry one mixestwo substances to observe their interaction. They are the target. Iwould call litmus paper a detector, but not human observation,which I put in (5) below. The apparatus of Atwood's machine for


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510 THE JOURNAL OF PHILOSOPHYdetermining local gravitational acceleration is a tuning fork with abrush on one prong. It is dropped so that the brush sweeps out acurve on the detector, a plate of glass with whitewash on it. There isno target materiel. Or is it the gravitational field?(4) There are theories or at least background lore about the ma-teriel. They help us design instruments, calculate how they will work,debug them, and run them. The phenomenology of each instrumentmay differ. Seldom (never?) is the phenomenological theory of aninstrument the same as the theory in question (1) or the systematictheory (2b). It may overlap with the topical hypotheses (2c). Forexample, the theory of the tuning fork has nothing much to do withthe theory of gravitational acceleration. Nowadays in big science,people who design detectors and people who prepare targets com-monly have very different expertise.(5) Data generators. In the past these were usually people likeGeorge Atwood measuring the length of the successive inflectionpoints of the curve swished out by the brush at the end of the tuningfork. Now we have printouts of automatic readings. A camera thattakes micrographs from an electron microscope once was a detector,now it is a data generator.(6) Data: the physical, material records produced by a datagenerator.(7) Data processing: a catch-all name for distinct activities thathave appeared at different stages in the history of science.(7a) Data assessment: e.g., the calculation of a probable error,using a formal procedure that is theory-neutral. There are also esti-mates of systematic error based on theories of the detector, appa-ratus, and target, and on deductions from topical hypotheses.(7b) Data reduction: indigestible or unintelligible information istransformed by statistical techniques into manageable quantities ordisplays.(7c) Data analysis, well-described by Peter Galison for high energyphysics: the "events" under study-preserved, e.g., as tracks on pho-tographs-were once selected and given preliminary analysis bysemi-skilled labor. With the advent of very fast detectors, a tape ofevents had to be analyzed by computer. The technicians weretrained, and later the programs were written, in the light of bothtopical hypotheses and theories of the instruments. Computer simu-lation of missing bits of data, and image enhancement, provide fur-ther examples of data processing.(8) Interpretation of the (processed) data: in the simplest casesthis is a single stage: a series of trials on Atwood's machine gives us aset of pairs of distances (between swishes) and times; we then com-


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PHILOSOPHICAL SIGNIFICANCE OF EXPERIMENTATION 511pute the gravitational acceleration g according to the Galilean for-mula g = 2s/t2. We need no topical hypotheses. Unfortunately, rea-soning like that used for Atwood's machine is the model for toomuch philosophical discussion of theory and experiment.

EXTENDING PIERRE DUHEM'S THESISHow is an "acceptable" experimental result obtained? Duhem ob-served that, if an experiment or observation is persistently inconsis-tent with a systematic theory, you need not abandon the theory, forin principle you can revise the theory of the instrument. In his exam-ple, revise astronomy or revise the theory of the telescope. Now, ifyou did the latter, you would probably rebuild your telescope, creat-ing a substantially different instrument! Andy Pickering importantlyadvances Duhem's idea by adding the materiel to the items that canbe modified.He regards the systematic theory, the instruments, and theories ofthe instruments as three plastic resources which the investigatorbrings into a mutual adjustment. His example has two competingtheories in question: free charges come either in units of e, thecharge of the electron, or else l/se (free quarks). In the background(2a) these are the only two possibilities. The materiel is an upgradedMillikan oil-drop device. The initial results of the experiment de-scribed seemed to show pretty much a continuum of minimum elec-tric charges. The experimenter modified both his theory of the appa-ratus and the apparatus (he revised the phenomenological theory ofcondenser plates, and repositioned the plates). The ensuing datawere interpreted as refuting the theory of free quarks.Duhem emphasized my elements (2) and (4). Pickering restored usto experimental practice by adding (3). Robert Ackermann attends toyet other elements, adding not only the instruments (3) but also thedata (6) and interpretation (8). Like Duhem and unlike Pickering, hehas a passive attitude to instruments, treating them as if they were"off-the-shelf" devices in the way that a navigator would use achronometer, or a cell biologist a nuclear magnetic resonance spec-trometer. What were once experimental and thoroughly "plastic"instruments become reliable technology.In Ackermann's account, instruments produce data that are liter-ally "given." The data are not theory-laden; they are material arti-facts, photographs, or inscriptions, the productions of instruments.Theory enters when they are interpreted. Science is a dialecticalaffair of fitting data and theory together. Data that at one time arejust "noises" may later be interpreted by a new theory. Thus, afterthe theory of pulsars was in place, older astrophysical records wereshown to be rich in evidence of pulsars. Those records were not


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512 THE JOURNAL OF PHILOSOPHYtheory-laden, but their interpretation is, on Ackermann's view, amatter of theory.

Thus, Duhem, Ackermann, and Pickering point to different kindsof interplay among some of the elements (1-8). In fact, all eight areplastic resources. We can (1) change questions, or more commonlymodify or sharpen them in midexperiment. Data (6) can be aban-doned or selected without fraud. Data processing (7) is almost em-barrassingly plastic. Those familiar with the logic of statistical infer-ence will be well aware of the hazards of data reduction (7b). Dataanalysis (7c) is plastic in an entirely different way. Its computer pro-grams are highly susceptible to modifications in the theory of target,apparatus, or detector-not to mention material changes made inthe way that those systems operate. One aim of developing a taxon-omy such as (1-8) is to describe a complex pattern of adjustmentswhich concludes with stable science resistant to revision.MATURITY AND STABILITYHere is a very liberal adaptation of Ackermann's picture of maturingscience. A collection of kinds of instruments evolves, hand in handwith theories that interpret the data that it produces. Ackermanncalls a collection producing data that comes to fall under a systematictheory an instrumentarium. As a matter of brute contingent fact,instrumentaria and systematic theories mature, and data uninter-pretable by theories are not generated. There is no drive for revisionof the theory, because it has acquired a stable data domain. What welater see as limitations of a theory are not even perceived as data.Thus, geometrical optics takes no cognizance of the fact that allshadows have blurred edges. The fine structure of shadows requiresan instrumentarium quite different from lenses and mirrors, to-gether with new systematic theory and topical hypotheses to inter-pret it.But is not at most one theory true, the old mature one, or theaspiring new one that takes account of the additional data domain?The metaphysical doctrine of the unity of science demands that. Butthink instead of the theories being different representations of sev-eral aspects of "the same reality." Niels Bohr tried to mitigate theshock of such a way of thinking by invoking complementarity, but weshould reach further than that. New sense is given to the idea ofincommensurability: these theories are incommensurable in Kuhn'sintended sense of "no common measure." The measure of the ma-ture theory is its data domain, which it fits within tolerances of error;the new theory tries to measure up to a new data domain.Philosophers from Susan Stebbing have mocked A. S. Eddington'sremark that he had two tables before him. Well, there is only one


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PHILOSOPHICAL SIGNIFICANCE OF EXPERIMENTATION 513table. But we should think out a semantics of representation, inwhich many commonsense beliefs about the table are literally true, aswere many of the things said by 1920s physics, and as are those heldby quantum field theory. There is one table, and many incommen-surable truths about it.So much I take to be a liberal extension of Ackermann's sugges-tions. Two things are importantly missing. One is the long haul ofgetting to a mature theory, which I believe is best described by anequally liberal extension of Pickering's account of apparatus andapparatus theory as a plastic resource. The other is the role of thoseelements, in my taxonomy, which Ackermann does not mention. Thechief practical indeterminacy of science lies not in the possible thingsone can do with the world or in the possible systematic theories onemay entertain, but in the manifold of models and approximationswhich constitute topical hypotheses. Topical hypotheses are under-determined. A theory does not say how it will be articulated to meshwith the world, nor does processed data say how they will be inter-preted by topical hypotheses. There are lots of ways to do it, andevery phenomenologist has a battery of such techniques. Kuhn hasimportantly emphasized that learning a science is not learning thesystematic theory but learning how to do the problems at the end ofthe chapter. A casual inspection of many textbooks will show that,aside from certain mathematical tricks of calculation, these problemsare typically training in how to use what I have been calling topicalhypotheses. A mature science achieves a canonical set of approxima-tions, the glue that holds it together, and which enable us to say thatthe theory is true of its data domain. The pain in hardworkingscience is the construction of new topical hypotheses. That is the"puzzle" to which so much "normal science" is addressed.THESES AND QUERIES(1) Scientific realism. All that I have said is consistent with scientificrealism about entities. My description of mature and successor nor-mal science strongly resembles Duhem's antirealism about theories. Iattribute to him the conception that nature, and even "mechanics"or "optics," is too complex to admit of a single unified description.One can at best aim at characterizing an aspect of parts of nature,and this is achieved by complementary mature theories that need notbe commensurable. But 'aspect' is no longer merely a metaphor, forit is to be explicated in terms of the structure of instruments, pro-cessed data, and topical hypotheses.(2) Truth. Do we need a new semantics for real science, one thatis based on the locution, 'true to the facts'-not the facts about some


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514 THE JOURNAL OF PHILOSOPHYmetaphysical world, but the facts about the phenomena created byexperimentalists?(3) Kuhnian revolutions. Not all scientific revolutions are Kuh-nian, witness "the" scientific revolution of the seventeenth century.It has been argued that there was a scientific revolution in geologyleading up to plate techtonics, but lacking the stage of crisis whichprecedes paradigm shift. Conjecture: revolutions with Kuhnianstructure are of two sorts. One occurs when a paradigm is imposedon a preparadigmatic field. The other sort occurs in mature sciencesprecisely when a new instrumentarium generates data outside anestablished data domain. That fits the "function" that Kuhn finds formeasurement in the physical sciences, and his own study of black bodyradiation.(4) Laboratory technology and the unity of science. When an in-strument becomes an off-the-shelf device for one branch of science,it can often be incorporated, after painful adjustments, into another.X-ray diffraction, designed for crystallography, engenders molecu-lar biology. The instrument theory of one science becomes built intothe practice of another. Insofar as topical and instrument theoriesinteract, there is a resultant unification of data domains, and hencean apparent unification or at least congruity among sciences.

IAN HACKINGUniversity of Toronto

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