theory on different occasions); and, third, the unity of science. 2. Let me start by indicating what I mean by cross-theoretical explanation and by delimiting some of ...
RICHARD
CONCEPTUAL
M. B U R I A N
CHANGE, CROSS-THEORETICAL
EXPLANATION,
AND THE UNITY OF SCIENCE
1. In accordance with the theme of this conference 1, I have chosen to discuss a topic which I believe will dominate philosophy of science (though not, perhaps, the philosophy of the particular sciences) in the next ten years. This topic is conceptual change in science. As post-Kuhnians, we have all heard much talk about the problem of conceptual change. I think, however, that there is no single problem or set of problems here, but a great variety of interlocking puzzles, many of which are as yet ill-defined and poorly articulated. Some of these problems concern surface dit~culties; many others (e.g., a number of the quandries surrounding counter-factuals) are probably artefacts of the analytical tools we employ. Other problems concerning conceptual change are, I believe, deep and fundamental- including, e.g., the problem of the precise role which can be played by logical analysis of scientific theories as a tool for understanding the nature of progress and change in science. Ideally, in this complex situation, one should make some preliminary attempt to separate technical from foundational questions and to delimit the problems one wishes to address. Today, however, rather than searching for a clear articulation of what we need to know about conceptual change, I shall plunge right in, addressing three themes which seem to me to touch on fundamental - indeed, foundational - problems. By sketching some of the interconnections among my themes, I hope to suggest the elements of a research program which might well shed some light on the problems of conceptual change. My themes are, first, explanation and, in particular, what I shall call cross-theoretical explanation; second, the criteria of identity for theories (or, if you prefer, the means by which we identify and re-identify the same theory on different occasions); and, third, the unity of science. 2. Let me start by indicating what I mean by cross-theoretical explanation and by delimiting some of the problems with which I am concerned under this rubric. In Kuhn and Feyerabend, one often encounters the claim that Synthese 32 (1975) 1-28. All Rights Reserved Copyright © 1975 by D. Reidel Publishing Company, Dordrecht-Holland
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certain theories - e.g., Newtonian mechanics and the special theory of relativity (STR) - are incommensurable,z There are a great variety of ways in which this claim has been read, but for present purposes a radical reading favored by Feyerabend is of particular interest. On this reading, to maintain that two theories are incommensurable is to maintain that there can be no logical contact between the claims of the one theory and the claims of the other 3 _ at least as long as the theories are not treated as 'mere' instruments of calculation. Given this account of incommensurability, there are immediate and serious difficulties concerning the impossibility of explanations cutting across theoretical contexts when the theories concerned are incommensurable. After all, we needn't be Hempelians for it to seem plausible that a necessary condition of explanation is that the explanans and the explauandum may be placed in logical contact with one another. 4 And ff it should turn out that (say) Newtonian mechanics and STR are incommensurable in the way I have indicated, then, contrary to almost all the orthodox views of the recent past, Newtonian claims cannot be explained on relativistic premises, and (on the standard Nagelian analysis of reduction) Newtonian mechanics cannot be reduced to relativity theory. In short, the present interpretation of incommensurability would force us to treat the rejection of one theory in favor of an incommensurable alternative as an extremely radical conceptual change rather than 'mere' change of belief. Such conceptual changes, should they ever occur, would disrupt all of the standard accounts of explanation, induction, rationality of theory choice, etc. How shall we deal with cross-theoretical explanation? How close to this radical extreme does (can, should) science come? There are any number of reasonable starting points. We might, e.g., proceed by a series of case studies. The time constraints of this symposium do not allow such an approach t o d a y - and in any event, not all of the issues involved can be resolved by case studies alone; some of the most interesting kinds of conceptual transitions may not yet have been historically exemplified. Again, we might proceed by seeking to establish norms which ought to govern the scientist who faces specific theoretical difficulties or which ought to govern the philosophical interpretation of ease histories. If, as has sometimes been argued, the best way for the scientist or the philosopher to proceed would be one in which logical contact with prior theories was
CONCEPTUAL CHANGE
always maintained, the threat posed by the logical possibility o f incommensurability would be significantly undercut. I am in considerable sympathy with some aspects of this second approach and will make some connection with it toward the end of the paper, but I propose to take a third path today. My path will be to examine the ways in which theories can approach incommensurability and nonetheless properly be said to compete. This path will lead us into a long excursis concerning the nature and identity of theories - an excursis which will prove of considerable assistance when we return later to cross-theoretical explanation and the problem of establishing logical contact between supposedly incommensurable theories. It is sometimes argued that no two theories can be incommensurable. But this seems to me to be a mistake. Under some very plausible (though debatable) assumptions, the general theory of relativity and Festinger's theory of cognitive dissonance are incommensurable. But if true, this is entirely uninteresting. The interesting challenge to the radical account of incommensurability amounts to the claim that there are - or, rather, that there can be - no competing theories which are incommensurable. By now this challenge is well-known,~ and it is surely serious, although many of the arguments used to support it fall short of the mark. 6 The basic point at stake here is that competing theories must make differing claims about the same entities or about what will eventuate on the same occasions. From this it follows that there must be some way of identifying some of the entities or occasions talked about by use of one theory with the entities or occasions talked about by use of its competitor. It follows from this, it is argued, that it is possible to establish logical contact between any competing theories. For immediate purposes, it is sufficient to note that if we are to resolve the issue whether incommensurable theories can compete, we shall have to turn to at least two further frontiers of debate - the means by which we identify and delimit theories, one from another, and the means by which we identify the entities or occasions which may properly be talked about by means of a given theory. Since the latter topic would land us in the morass of the theory of meaning, it will not be possible to tackle it head on within the confines of this limited paper (though I will drop a few hints about it) - but I will deal directly with the way we delimit theories. Keep in mind that the question to which we wish to return is how two radically
4
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different theories can compete with each other in trying to explain some phenomenon; this limitation on our purposes will help to limit the discussion of the identity theories and the meaning of theoretical claims. 3. In order to set some background for my, own views about the way theories are - or ought to be - identified, I will start by objecting to two standard, but only partially adequate views. The first is the familiar Carnap-Nagel-Hempel view on which a theory is to be understood as a calculus plus a set of correspondence rules tying the calculus to an observation base. As a convenient shorthand, I shall refer to any analysis which separates the observation language from the theoretical language in this manner as a two-tiered analysis of the language of science. When I say an analysis is two-tiered, I mean to say only that the observation language is supposed to be independent of the theoretical language, not that the theoretical language is innocent of 'levels of complexity' or that there are no 'terms designating emergents' in the theoretical language. The second view I will reject is the more recently popular one which holds that there can be no epistemologically viable separation of the observation language from the theoretical language (whence I will call such an analysis onetiered), but that the connection between languages and theories is sufficiently intimate that one may 'read off' a person's theoretical commitments (or, perhaps, his 'deepest' theoretical commitments) from the language he speaks. The two-tiered analysis has deeply empiricist roots. It seeks to uncover the observational basis of all empirical knowledge. Accordingly, it treats hypotheses and theories as systematic ways of stating connections among observations or observation claims where observations are treated as epistemically privileged sources of knowledge about the actual world and are thought to be secured, understood and reported independently of theoretical knowledge. Theories, on this view, are means of systematizing experience; they cannot correct experience (though they may explain or predict it), but they may be corrected by it. Similarly, on the standard logical empiricist apparatus, empirical meaningfulness has its source solely in the observation base; it is imported into the theory via the correspondence rules and is never exported from the theory to the observation base. 7 Without the correspondence rules, a theory would be a 'pure' calculus with no independent empirical meaning.
CONCEPTUAL
CHANGE
I will challenge this position, but the full thrust of my argument will not be clear until the end of Section 8. The treatment of theories as calculi plus correspondence rules resolves certain difficulties concerning the criteria of identity for theories though, as we shall see, it encounters others. The proposals available to logical empiricists governing the ways of identifying or reidentifying a given theory by means of its canonical logistic reformulation s fall between two initially plausible extremes, both fraught with highly counterintuitive consequences. On the first of these, two formulations express the same theory if and only if they employ the same theoretical calculus. But it would be perfectly feasible to employ the same theoretical calculus in a wave theory of sound and a wave theory of light without in the least reducing sound to light or the wave theory of sound to the wave theory of light. And, indeed, innumerable attempts have been made to employ familiar calculi (e.g. of fluid flow) in new ways (to deal with heat flow) without necessarily identifying the two theories built upon the same calculus. Roughly speaking, within a two-tiered analysis, a necessary condition for identifying two formulations as formulations of the same theory is that they share some common external (i.e. observational) subject matter. This condition is violated if one identifies a theory with its calculus. The other extreme position within the two-tiered approach identifies a theory by its empirical consequences. The difficulty here is that at a given moment of time (employing the then-current auxiliary assumptions), the empirical consequences of, say, a wave and a particle theory of light might be identical. Yet how many of us are such thoroughgoing instrumentalists as to suggest that this particular wave theory and this particular particle theory are therefore 'the same' theory ? One of the strengths of the standard Carnap-Nagel-Hempel account is that it resolves these difficulties by requiring two formulations to incorporate the same theoretical calculus and the same empirical consequences if they are to formulate the same theory. 4. Both of these extreme approaches - and, indeed, almost all of the "middle' approaches which combine criteria concerning calculus structure with those concerning empirical consequences - commit a fundamental error. They restrict their concern to a 'still photograph' (the phrase is Bob Causey's) of the theory. I.e., they freeze the theory at a particular moment
R I C H A R D M. B U R I A N
in time and try to analyze it, identify it, and justify its acceptance from its momentary characteristics. In fact, in identifying and reidentifying 'the same' theory in different formulations, we are normally not concerned merely with a given moment of time, with a listing of empirical consequences, or with the structure of a theoretical calculus. Our concern is normally diachronic, and requires us to reidentify 'the same' theory against different backgrounds of knowledge and in spite of the fact that its empirical consequences and its calculus have changed. 9 Putting the point somewhat differently, the logical empiricists provide us with highly 'cooked' formulations of theories - logistically kosher rational reconstructions of 'finished' theories in the context of justification. But a theory which is 'cooked' in this way is already dead; it must have already undergone all the adventures which make it a viable candidate for the scientist's attention and the changes which these adventures have wrought in it. To ask after the criteria of identity of a dead theory is perhaps the least interesting and least useful way of putting the problem, for the significant difficulties in delimiting different formulations of the same theory arise most sharply while it is still in flux, while it is being revised and improved under the pressure of criticism, testing, and comparison with alternatives. Theories, like people, are born, grow, develop, adapt to new circumstances, have powers which wax and wane, etc., etc. Like people, they very seldom conform to a neatly organized set of ideal types. In 'real life,' reidentifying them often requires comparing different stages of their histories. And just as Richard Nixon at the age of two was - if barely so the same person as the Richard Nixon many have come, alas, to despise, so the Bohr theory of the hydrogen atom in 1913 was - but arguably so 'the same' theory as the Bohr theory of 1924.1° The criteria of identity for theories must take into account this dynamic aspect ;~ no criteria based on a single temporal cross-section can suffice - even if the cross-section is taken at a time when the theory has reached some kind of apotheosis. It should now be clear why the hypothesized wave and particle theories of light with (temporarily) identical empirical consequences are not at all 'the same' theory. Each promises a radically different denouement in the growth of our knowledge about light. And this promise, with its dynamical component, is an important property of the theory usable in its r eidentification.
CONCEPTUAL CHANGE
7
5. Toward the end of this paper I will pick up the theme of the dynamical component in theory identification in order to connect it with my discussion of the unity of science. But first, I must turn, as promised, toward a second approach to the identity of theories - an approach which connects theories to whole languages and attempts to tease out the desired criteria of identity for theories by means of an examination of the correlated language. The view I am about to discuss may be treated as a development of a second set of criticisms of the two-tiered analysis of the language of science. I take it as familiar dogma these days, accepted even by such 'conservatives' as Hempel and Scheflter, that all empirical claims couched in a public language are subject to correction. 12 It is also frequently argued-most emphatically by Feyerabend,13 but also by Hanson, Kuhn, Popper, Toulmin and others - that such correction may be based on theoretical rather than observational developments. When such corrections occur, the very category scheme of the observation language is altered for theoretical reasons. Such alterations, it is argued, show that the traditional distinction between observation language and theoretical language has been undermined. In consequence, all of the thinkers cited advocate some form of one-tiered analysis of the language of science. Now the position I wish to discuss goes beyond the claim that the language of science is one-tiered. It adds that any language reflects the expectations of the language using community, and in particular its expectations of regularity. Thus, the language as a whole reflects the basic theory or theories of the community in question. In contrast with the two-tiered analysis, it treats theories as essentially connected to languages, not calculi-associated-with-languages. I must add a cautionary note. It would clearly be wrong to identify a theory with a language like English (as opposed, for example, to German), for it is not the linguistic clothing (the phonemes and the typographical symbols), but the response roles and inferential roles played by linguistic tokens which are of importance here. The concept of a theory, on the account we are considering, is the concept of a conceptual structure 14 which two languages may share. Such conceptual structures are, broadly speaking, linguistic entities - but it is of critical importance to realize that they are interlinguistic, and not language-specific, in character. How are we to judge whether two bits of language express the same
R I C H A R D M. B U R I A N
theory (in the sense of 'theory' under examination)? To answer this, one needs to know the roles of the bits within their respective linguistic contexts; no criteria 'external' to these contexts will suffice to yield an answer to this question. Consider, for example, the French sentence, 'Le livre est sur la table,' and the English sentence, 'The book is on the table.' Three groups of criteria are relevant to the question whether the same 'theory' is correlated with these sentences - applicational, inferential and mixed applicational-jnferential criteria. Applicational: Are these sentences used, eeteris paribus, on appropriately similar occasions by French and English speakers? 1~ Inferential: Are the inference classes for each of these sentences structurally similar? 16 Mixed applicational and inferential: For those sentences of one language which are inferentiaUy connected with one of our original sentences and which have an observational application, does the structurally parallel sentence (or sentences) of the other language have a parallel observational use? If the answer to all of these questions is 'yes', then there is a good prima facie case for the claim that our original sentences fit into the same theory. This case can be strengthened by expanding the range of sentences interlocking with our original sentences for which parallelism holds. Similarity of structure and of observational application are matters of degree. Nonetheless, it seems obvious that for most purposes the overwhelming similarities between the two sentences of the present example will support the judgment that they correlate with the same 'theory'. Now although this technique works extremely well for fairly delimited pieces of language, it seems to me fundamentally mistaken when applied to languages as wholes. It is fairly commonly held nowadays, largely on the basis of a variety of 'local' examples like the one just discussed, that French and English express the same fundamental theory - call it Western and that this theory is the common interlinguistic core of at least all of the major Western languages. 17 This view is often supported by arguments purporting to show that all Western languages have (more or less) the same depth grammar and (more or less) the same points of observational application. ~s It is also sometimes held that some non-Western languages exemplify radically different theories than Western, 19 and that the languages of various scientific theories when fully developed, would be radically incomparable with Western. 2°
CONCEPTUAL CHANGE
To the extent that these views amount to a commitment to the claim that a single theory (or conceptual scheme or metaphysics) can properly be associated with a natural language, they all strike me as radically false. Strawson and others to the contrary notwithstanding, there is no single metaphysics, no single theory, no single conceptual scheme implicit in English or in any other natural language. Feyerabend to the contrary notwithstanding, we are able to express Aristotle's, Buridan's, Newton's, Einstein's, and Bohr's theories of matter and motion in (technically supplemented) English. Each of these theories has its own inferential structure and its own applications to the world. The fact that they may all be formulated within a single natural language shows that there are serious difficulties in supposing that there is a single (interlinguistic) conceptual structure underlying a natural language. $1 I do not mean to suggest that the use of a language carries with it no metaphysical or theoretical commitments, nor that there are no coherent conceptual schemes. Rather, I mean to suggest that unless one places rigid technical limitations on one's language, that language will reflect a jumble of inchoate, partially developed, potentially competing theories and metaphysics, each of them in a fragmentary state of elaboration. In short, languages reflect their histories. The inferential structure of a natural language is a mirror of the language community's many false starts, metaphysical confusions, changes of theory, prevalent metaphors, etc. A natural language allows one to state many theories, including conflicting ones and partially developed ones which, if they mature, will conflict with the currently prevalent theories. Accordingly, if we mean by a theory something which has an inferential structure as 'narrowly' delimited as, say, Newtonian mechanics, no single theory or set of mutually compatible theories is uniquely associated with a natural language. The approach to the problem of specifying criteria of identity for theories which supposes a unique association between a given language and its theory is a failure. 6. At this point, I must offer some sort of alternative of my own. z~ I have argued that theories are not be to identified by their calculi (with or without correspondence rules), nor by their external (observational) subject matter, nor by 'the' interlinguistic conceptual structure of the language employed by the theorist. I have also argued that it will be necessary to
10
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treat theories as continuants which undergo change and have histories and which are to be identified in ways connected with their promissory notes about future developments. It is in this connection that we will soon encounter another of my themes - the unity of science. By far the best developed account of the dynamic, heuristic and pragmatic aspect of theories (though I have my disagreements with it) is to be found in the late Imre Lakatos's 'Methodology of Research Programrues.' I shall presume that this audience is familiar, at least in outline, with his notions of the 'hard core' of a theory, and the 'protective belt' of auxiliary hypotheses surrounding that core, and with the outlines of Lakatos's attempts to determine whether a research program is progressing or stagnating. A related approach, but one which is far less developed and precise, is Arne Naess's. Naess treats a theory as having a leading idea or set of leading ideas as its core. The central difference between Naess and Lakatos for present purposes is that Naess's core need not be hard. Leading ideas may be vague and suggestive; part of the 'professional' development of a theory involves elaborating and developing it so that its leading ideas become 'hard'. I am inclined to Naess's rather than Lakatos's approach. Even when the term, 'theory,' is limited in application to the fundamental theories of the theoretical sciences, it is an 'accordion term'. It stretches to cover large scale metaphysical programs ('the atomic theory of matter '23) and squeezes to cover higMy systematic, rigid, and precise accounts of relatively narrow ranges of phenomena ('the [original, non-relativistic] Bohr theory of the hydrogen atom'24). It should be clear that leading ideas alone do not constitute a theory. They are what is common to different, perhaps competing, perhaps even mutually incompatible versions of the same theory. Taken in isolation, leading ideas are too vague and indeterminate to yield predictions, explanations, or descriptions; they are too ambiguous (as they must be to allow a variety of elaborations) to say much of anything about the world. They form a part of a metaphysics or a research program which becomes capable of empirical use only when means are found to make their inferential connections precise and to specify rigorously their correct empirical application. (Consider the difficulty until this century of answering the question, 'which empiricaUy identifiable entities are atoms 7')
CONCEPTUAL CHANGE
11
A theory, then, cannot be identified with (though it may be identified by reference to) its leading ideas. Nor can it be identified with any of its versions (or even all of its historically extant versions), for the refutation of any or all of those versions does not constitute the refutation of the theory. Indeed, typically, Kepler's 'refutation' of Copernicus's original version of his theory of the heavens, the Mendelian 'refutation' of Darwin's account of evolution, and Sommerfeld's relativistic correction of Bohr's original model of the atom are all now commonly regarded as corroborations of the theories, one version of which they refuted. A theory in the sense of the term which I am developing must meet at least the following conditions:
(1)
(2)
(3)
Some leading terms and/or claims of the theory must have empirical application. There must be definite ways in which the extant version of the theory can be shown to be mistaken (though these ways need not be locally detectable)/'5 A version of a theory is mistaken when it fails to describe properly or to explain properly phenomena falling within its intended domain. There must be ways of protecting the leading ideas of the theory and incorporating them into new versions of the same theory shotdd the currently accepted version be refuted or abandoned as inadequate in the face of appropriate evidence and competitive pressures.
We are now in a position to appreciate a great many of the strengths and weaknesses of the other accounts of theories discussed above. A theory, when it is born, involves the tentative application of some leading ideas to a range of experience already conceptualized in some way or other. It must not only be tentative, it must be grafted onto a pre-existing account of the phenomena in question. As a result, theories are typically born with two tiers; there is a pre-existing observation language in terms of which the explanandum is (and is properly) stated, and there is a special language of the theory built, typically on a 'new' metaphysics. Initially, and later, in times of crisis - theories are judged in part by their ability to mimic the 'natural' observational description of the phenomena which they attempt to explain. This two-tiered arrangement is methodologically
12
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M. B U R I A N
indispensable for the introduction and evaluation of nascent theories. Thus far forth, there is a close fit between the present account and the standard logical empiricist one. On the other hand, theories are not interpreted calculi, but are wouldbe world pictures (or partial world pictures). The key difference is that at least when they acquire a relatively 'hard' formulation, they have empirical meaning independent of that of the observation language. There is an 'internal subject matter' - e.g., atoms - which is properly the primary subject matter of the theory. Terms designating this internal subject matter may in principle (and sometimes in practice) be connected 'directly' to the world without mediation of the old observation language. At this stage, the theory may still be fit, more or less, into a two-tiered approach, but it must be recognized that empirical meaning passes 'down' from the theory to the observation language as well as 'up' from the observation language to the theory. It is this independent empirical meaning which can guide the scientist in the choice of new correspondence rules when he applies the theory to a new domain, i.e., to a domain to which it has not yet been connected by correspondence rules. There are two key ways of supporting the claim that empirical meaning can pass 'down' from the theory to the observation language. The first rests on the fact that theories often yield singular claims (subsequently borne out) about the composition or nature of particular items ('This sample of hydrogen is composed of .~ 1023 atoms') - claims which are not observationaUy meaningful with respect to the pre-existing observation base. The second is based on the fact that the empirical laws derived from a theory typically differ from inductive generalizations at or below the range of observational error pertaining at the time of derivation of the laws. Thus, in Newtonian mechanics, when one takes perturbations of planetary orbits into account, deviations from (Keplerian)elliptical orbits are predictable - and these precise deviations have subsequently been observed. Since such departures from accepted experimental laws often prove testable, the theoretical premises must have empirical content not imported into the theory by the correspondence rules. 26 The role of the independent empirical meaning of theoretical claims in determining the choice of correspondence rules is stressed by M. Hesse. 27 Following Campbell, Hesse employs the example of the derivation of correspondence rules connecting certain claims of the kinetic
CONCEPTUAL CHANGE
13
theory of heat with claims about the viscosity of gases. Since the old correspondence rules connected the kinetic theory to such variables as temperature, pressure, and volume, and since no adequate observational connections between these variables and viscosity were available, the fact that the new correspondence rules were not arbitrary can be due only to the direct relevance of theoretical claims about the atomic structure of gases to viscosity. All this suggests that the one-tiered analysis of the language of science has also captured a truth of central importance: a completely successful theory would offer an alternative and demonstrably more accurate description of even familiar observed phenomena (not to mention phenomena not readily described in the observation language) than is as yet available. To this extent, the observational descriptions of even familiar phenomena should, ideally, be revised in accordance with the leading ideas of the best available theory when it is sufficiently developed. Accordingly, correspondence rules might well be interpreted, as Sellars suggests, 2s as stating potential identifications of 'observational' with 'theoretical' phenomena - identifications which are included among the promissory notes of the theory. One must put such identifications carefully, for they deny that the original observational characterization of the phenomenon in question was correct. Thus, e.g., an atomic theory of matter claims that ultimately we will be forced to recognize that tables, which were once thought to be Aristotelian continua (a belief still reflected in our language) are really discontinuous. Typically, our theories are neither sufficiently encompassing nor sufficiently exactly developed to warrant immediate replacement of observation-language with theoretical-language descriptions of familiar phenomena. And even if epistemologieal warrant were available for such replacement, practical considerations might present the replacement from being carried out except in rather extraordinary circumstances. As a result, we can locate rather concretely one of the forward-looking aspects of a theory - an aspect which may be used to differentiate if from even those competitors which at a given moment exhibit very similar empirical consequences. The denouement promised by a particle theory of light is one in which light, in all of its interactions, is redescribed as a group of moving particles interacting with other forms of matter in a completely anomaly-
14
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free manner. The denouement promised by a wave theory of light is one in which light in all of its interactions is redescribed via the interaction of travelling waves with various forms of matter - again in a completely anomaly-free manner. Clearly these denouements are not compossible. The (classical) wave and the particle theories of light cannot both be true. I conclude that one of the most important 'dynamic' components relevant to the identification of a theory is its promise to replace 'incorrect' observational descriptions with finer-grained, testably more accurate observational descriptions conforming to the leading ideas of the theory. 7. After this long excursis, it is time to return to cross-theoretical explanation and the unity of science. M y first remark about cross-theoretical explanation is that there is a strong tendency for it to be non-Hempelian. O f course, instrumentalist strategems m a y always be employed to force any two-tiered structure into the Hempelian mold, but to the extent that the tendency of theories to establish their own observation bases is honored, to,the extent that the implicit metaphysics of a theory is allowed to enter its empirical content - to that extent significantly differing theories will be incomparable. As Naess puts it: No theoretical or practical work aiming at testing certain theoretical laws or a definite theory, taken in isolation, can bring forth evidence against the basic conceptual structure of the theory. The worst that can happen to a molecular theory is that it seems that molecules behave very differently from what the theory says - that they have quite different properties. But this does not refute the existence of molecules, or invalidate the concept 'molecule' in the basic structure of the theory. (1971, pp. 48-9, Naess's emphasis.) If the theoretical ideas behind two theories are dearly different, it is unlikely that the one can embrace the other as a special case, or that the one is 'more comprehensive than' the other, taking this relation to be an explicit relation between professionally adequate versions. Prima facie there is evidence that those people are right who insist that classical mechanics cannot be shown to be a special case within relativistic mechanics, or quantum physics to be more comprehensive than classical. One would expect, instead, a relation of incomparability due to basic differences of conceptual structure. (Ibid., p. 66, my emphasis.)
The point requires careful articulation. To the extent that fully carrying out the implicit program of a given theory requires the replacement o f familiar descriptions of experientially familiar (but also unfamiliar) phenomena with descriptions falling within the theory, the theory (a)
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15
denies the existence of the phenomena as formerly described, and (b) strictly speaking cannot allow a description of those phenomena as they used to be conceived. Thus, depending on some technicalities concerning the language in which a theory is expressed, full-out adoption of a theory radicaUy departing from preceding views will either force one to deny the truth of the explanandum when that explanandum is stated in the old terminology (weak version) or prevent one entirely from formulating the old explanandum (strong version). In either case, deduction of the old explanandum (or its probability) from premises acceptable within the new theory will be impossible. Since 'full-out adoption of a theory' (whatever, precisely, that means) brings with it this consequence - the denial of the correctness of extraordinarily well-entrenched observation statements - one will not be willing or able to take this step without being very thoroughly sure of one's ground. On the other hand, if full-out adoption of a theory is, in epistemological principle, possible, then the standard attempts (e.g., Achinstein's, Kordig's, Scheffler's) to show the foundational impossibility of radical revolutions in which the whole observations base is abandoned for theoretical reasons must be mistaken. 8. Since so much of this dispute seems to turn on the debates over 'radical meaning variance' I cannot forego the opportunity to drop a hint or two about the theory of meaning. It will perhaps have been noticed that in my prime examples (wave vs. particle theories of light, Newtonian mechanics vs. STR), any number of terms ('light beam,' 'prism,' 'diffraction'; 'mass,' 'velocity,' 'meter stick') continue in use even though one theory comes to predominate where its competitor used to. It is very tempting to say that there is a common core of meaning which these terms exhibit in spite of these changes in theory. There are at least two ways in which this claim is partly right and partly wrong: (1) In both of these historical cases, the 'adoption' of one or another theory has never proceeded so far as to definitively cut loose from the preexisting observation base. To this extent, though in widely varying degrees, the adoption of the theories - and more especially of the corresponding theoretical languages - always involved a fair degree of 'as-ifishness.' And given the state of our knowledge, this was only appropriate. Accordingly, the replacement of the observational terms i~ their old
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meanings with (phonetically and typographically similar) terms infected with new meanings was only tentatively and partially carried out. (2) More fundamentally, and of great significance for the theory of meaning, one cannot simply look at the systemic interconnections (particularly syntactic and inferential ones) of a theoretical claim to know its meaning. If we are dealing with a theory rather than a theoretical calculus, the theory must be applied to our world. The very same theory can in principle have criteria of application at different levels. To illustrate the point: A kinetic theory of gases whose base, ontologically speaking, involves claims about the atoms and molecules which make up gases might in principle be applied directly 29 to atoms and molecules if we were able (as we are now not normally) to obtain information about the single atoms and molecules composing a gas. The theory might also, however, be applied directly only in claims about molar gases - i.e., large ensembles of atoms or molecules. This variation in the epistemological base of the theory need not affect its identity. But unless there is some level at which the theory has direct application, we do not have a theory at all, but only a calculus which might someday become a theory. And given a theory with some established application, that application (together with the structure of the theory) prohibits the adoption of a variety of rules of application at a variety of levels. E.g., billiard balls (the model entities for elementary kinetic theory) cannot be properly treated as if they were atoms for any number of reasons- including the reason that they do not combine into molecules in the manner prescribed by the theory. My moral is this: The rules of inference connecting the behavior of ensembles of atoms with the fundamental laws of atomic behavior, 3° together with those fundamental laws (and all the standard formation rules, etc.), do not suffice to establish the meaning of the terms and the claims of the atomic theory of gases. In addition, the criteria of application of the new theory (and the family of resultant potential criteria of application at various levels) are crucial to identifying the theory as a whole and to supplying the empirical meaning of its terms and claims. It follows that the criteria of application of terms like 'light' and 'mass' at the molar level are partially determinative of meaning. Since in all historically interesting cases, such terms have shown very great stability in certain applications, there is a dimension of continuity with respect to meaning not appreciated in the arguments for radical meaning variance. 31
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9. I have argued that taking theories seriously entails taking seriously the possibility that a theory may be articulated into an empirically adequate one-tiered account of the phenomena it explains - i.e., a n account in which the observation language is the same as the theoretical language. 82 I have also argued that to the extent that theories threaten to become one-tiered, cross-theoretical explanations threaten to become non-Hempelian. This suggests that two phenomena are commonly run together under the rubric of 'reductive explanation. 'a3 One is intra-theoretical explanation of what happens at a new level. E.g., in the kinetic theory of gases, one needs to deduce, with the help of auxiliary hypotheses, the behavior of large ensembles of atoms.84 Such intra-theoretic arguments may, so far forth, be presumed to be Hempelian in character. The other phenomenon, one which is easily confused with intra-theoretical new level explanation, is cross-theoretical explanation. Where cross-theoretical explanations involve two potentially incomparable schemes of description - i.e., where each theory if fully developed would exclude the other's descriptions of the phenomena under examination - there are serious difficulties concerning explanation. To insist that explanation be deductive while at the same time couching the explanandum in terms of one theory or in the observation language is to bar full development of the alternative theory. To allow each theory opportunity for full development is to abandon deductive structure as a necessary condition for cross-theoretical explanation. It is to allow for what many philosophers have labelled 'replacement' rather than 'reduction.' As scientists, we surely desire to maximize the breadth and the accuracy of each of our theories. This means that we should push them as far as possible in the direction of acquiring a one-tiered application. 35 But where we have competing theories, the resultant one-tiered descriptive schemes cannot both be true, cannot both remain empirically adequate over the long haul. So we now see connections opening up between the non-deductive character of (some) cross-theoretical explanations and the unity of science. 10. I will not be able to say as much as I would like about the unity of science today, partly because my own views on this topic are presently in flux. But at least three aspects of the unity of science bear on my discussion. These are (1) the methodological and meta-scientific character of
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the claim that science can be unified, (2) the deep connection of the thesis of the unity of science with the claim that truth is in some sense unitary, and (3) the consequences of adopting a methodology presupposing the unity of science for one's treatment of competing theories. To close this paper, I shall speak briefly to each of these topics. (1) The search for a unified science - the thesis that science can be unified - is as old as philosophy. This search, I maintain, is entirely legitimate. The world is as simple - or as complex - as it happens to be. Nothing we do, presumably, can alter that. Yet we can only learn how complex it is by seeking simplicities and admitting complications to the extent that we are forced to. As Einstein once said, the scientist, seeking laws of nature, should seek the simplest laws possible - but no simpler. Although a great number of specific theses which have recently been incorporated under the banner of the unity of science are false (for example that there can be no emergence in a unified science), the methodological core of the unity of science movement is sound; all theories bearing on a particular phenomenon must bear, somehow, on each other and should reflect the single (though perhaps complex) truth which that phenomenon occasions. And since theories concern, inter alia, the interconnections among various occurrences, this leads to the goal of a well-woven tapestry in which the various threads connect into a unified whole. This accords with the spirit, though not the letter, of the Neurath-Carnap attempt to capture the unity of science through the unity of its language. (2) This view is fraught with metaphysical and epistemological presuppositions. Among the deeper of these I include the presuppositions that the truth in a given matter is single and unified - that there is the truth; ~6 that there is but one world (however complex it may be) with which we are in contact; that the central task of science is to search out the truth about that world, its various parts, and their interconnections. It is, of course, arguable whether these presuppositions are true, whether we ought to adopt the goal of searching out the truth both generally and in particular contexts and whether, having adopted it, it will conflict with other goals which are of equal or greater importance to us. Such questions will not go away. But though they are philosophically crucial, I simply cannot address them today. Still, if you allow a characterization of the scientific enterprise along these lines, then to the extent that we choose to do science, we choose to
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follow a path which has a unified science as its ultimate objective. It must be admitted that there will be many strategic situations in which there are good reasons for pluralistic approaches - these situations may well be the norm. Unity is an ultimate, not an immediate, objective, and it may be best served by encouraging competition among theories. Furthermore, in concrete cases in the context of discovery, it is often unclear whether a particular theoretical revision will prove assimilable to a (perhaps minor) change within the then-current theory or whether it will force a chain of revisions which yield a new theory, organized around a new leading idea. Planck's well-known aversion to the development of quantum mechanics rests in part on his unhappiness with the fact that his quantum hypothesis proved unsusceptible to the former treatment, that the development of the hypothesis disrupted the classical theory (and standards of explanation) in which his hypothesis had its historical roots. 37 Nevertheles, a situation in which the best we have is a set of competing theories, a situation in which we are unable to avoid cross-theoretical explanations, a situation in which 'internal' modifications force entirely new theories on us, will be one which is inherently intellectually unsatisfactory. The chief virtue of basing one's methodology on the unity of science and on the search for the truth seems to me to be that one will not rest satisfied with empirical adequacy or with the fulfillment of immediate practical objectives. Even when no anomalies are sufficiently insistent to upset the narrow empiricist's faith in current theories, a situation may be so intellectually disturbing as to call forth a revolution. It is this, I think which is right in Holton's interpretation of what drove Einstein to devise the STR; 3s it was not such experimental anomalies as were revealed by the now notorious Michelson-Morley and other experiments, but the lack of symmetry and unity between Newton's mechanics and Maxwell's electrodynamics which moved Einstein. (3) Finally, a few words about the impact of a methodology based on the unity of science on our treatment of the problem of theory change. First, the adoption of such a methodology reinforces the tendency to insist that a truly adequate theory should supply its own observation language. To the extent that the truth is unitary, a single (though perhaps complexly layered or structured) category system must be adequate to represent it. Second, such a methodology requires one to treat competing theories (as opposed to competing versions of the same theory) via the mediation
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of some common language. To compete, theories must offer (however tentatively) alternative conceptual structures which purport to cover a common set of occurrences or phenomena. For us to recognize theory competition, we must recognize the overlap in the phenomena. This makes it methodologically essential that the theories be tied to a common observation language. Yet this tie cannot be perfect. It must be bought at the cost of a partial instrumentalism for each theory, since each theory, taken literally, would deny or disallow the prior observational account of the phenomena in question as well as the account offered by the competing theory. Finally, the methodology in question sets severe constraints on the transition from a two-tiered to a one-tiered application of a given theory. In order to justify full-fledged adoption of a particular theory, the methodology requires that theory to enable one to account for (a) the regularities and successes of competing theories as these successes are recorded in the observation framework, a9 and (b) for the success of the observation framework itself. To do this, the new theory must enable one to establish corrected accounts of phenomena hitherto described within the observation framework which enable one to account for the successes as well as the failures of the old observational descriptions. Usually this is accomplished by showing the (near) indistinguishability of the new from the old account given the hitherto relevant boundary conditions and margins of observational error. Thus, within the kinetic theory of heat, one can prove the observational indistinguishability of the deviations of the kinetic theory from the corrected phenomenological theory for old familiar cases (e.g., those sufficiently removed from absolute zero and involving enough molecules). For precisely these cases, the corrected phenomenological theory differs below the margin of observational error from the original phenomenological theory. One can account for the success of 'common sense' beliefs about heat in similar fashion.4° This constraint on the full-fledged adoption of a revolutionary theory should, I believe, enable one to understand the continuities in the development of science and to define the sense in which there is progress in science even in the face of the wildest variation in the fundamental ontology of our theories. Brandeis University, Waltham, Mass.
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NOTES 1 This paper is a slightly revised version of a paper delivered to a conference on 'The Next Ten Years in Philosophy of Science' sponsored by the Department of Philosophy of the State University of New York at Buffalo and the Buffalo Philosophy of Science Society. I would like to thank my friend, Prof. Neil Gallagher of SUNY at Buffalo, and the organizers of the conference - Peter Barker, Prof. Richard Hull, and Robert Lawson - for their kind support in a variety of matters. Thanks are also due to my student, Catherine Elgin, for several important criticisms which helped me to clarify my views at a number of important junctures in the argument. I am also grateful to Ms. Elgin and to Aiko Adachi for their assistance in typing various versions of the manuscript. 2 Cf. Kuhn (1970a), esp. Chapters IX and X, and Feyerabend (1962). Many other articles by Feyerabend develop this theme. a Feyerabend seems to mean not only that the claims of each theory are logically independent of the claims of the other (so that no claims of one theory may be deduced from premises taken from the other), but also that any attempt to conjoin, disjoin, or otherwise combine the claims of one theory with those of the other will restdt in incoherence. In a typical argument, he maintains that the attempt to connect relativistic and Newtonian descriptions of the motion of a body will necessarily be incoherent because such descriptions would require the assignment of matually incompatible logical forms to such fundamental terms as 'mass' and 'velocity' and because (supposing the first objection overcome) the conflicting descriptions would yield mutually contradictory entailments about the possible motions the body might acquire, etc. Cf. e.g. Feyerabend (1962), pp. 80ft. or Feyerabend (1965a), pp. 168ff. Ktthn disavows this interpretation of incommensurability in the 'Postscript' to his (1970a) and in his (1970b). It is not clear whether he can do so without considerably weakening some of his other views. On this topic, cf. Shapere (1971). 4 Thus Scriven's non-Hempelian analysis of explanation requires that one be able to justify the claim that A explains B. But the truth-justifying grounds which one may cite, typically, establish that there are premises (including premises describing A) from which one may deduce a conclusion (or the probability of a conclusion) describing B. So Striven would accept this necessary condition. Cf. e.g. Scriven (1962), esp. pp. 196ff. 5 A few of the better known sources for this challenge are: Achinstein (1964) and (1968), Kordig (1971) and elsewhere, Scheffler (1967), and Shapere (1964) and (1966). I took this approach myself in my (1971). e It is often argued, for example, that theories must have incompatible consequences if they are to compete; from this it would follow that competing theories cannot be incommensurable. Against this I cite the arguments of Israel Scheffler, himself no friend of incommensurability, in his (1967). Scheffler holds that most, if not all, of the cases in which Kuhn and Feyerabend allege competing theories to be incommensurable are spurious, arguing the matter in detail for a few eases in the course of Chapters 3 and 4. Nevertheless, he admits the theoretical possibility that paradigm shifts may result in incommensurability and argues that "lack of commensurability.., does not necessarily imply lack of comparability." (p. 82.) This argument is clarified and amplified in Martin (1971) and (1972). An interesting technical critique of this aspect of the logical empiricist approach, focusing primarily on Carnap, may be found in Child (1971). 8 Note that I am asking after the criteria of identity of the theories which serve as the
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analysandum for logistic analysis, not for the criteria of identity of the logistically reconstructed theory. Although I am skeptical whether all logistically equivalent reaxiomatizations of the conjunction of the theoretical postulates and the correspondence rules are eqaally perspicuous as analyses of a given theory, I am perfectly happy to suppose for the sake of argument that such problems are easily solved, being artefacts of technical defects in our analytical tools. My concern is the discrepancy between the criteria of identity for the (logistically proper) analysans and the (pre-logistic) analysandum. I am grateful to Prof. Richard Hull and to my student, Jon Adler, for helping me clarify the argument of this passage. Mr. Adler also convinced me of the need for note 3. 9 I was awakened to the importance of these considerations in good part by a recent reading of A. Naess (1971). 10 This example, like that of Richard Nixon, is chosen with malice aforethought. It is developed by Naess, ibid., pp. 64ff., and affords a glorious example of the tendency of theories to expand to cover large.r contexts. Thus Sommerfeld's relativistic version of Bohr's theory, published in 1915, is incompatible with Bohr's original formulation; yet it is uniformly held to have increased the support for the Bohr theory by predicting certain fine deviations of the hydrogen spectrum from the spectrum calculated by Bohr. (Cf., e.g. D'Abro, 1951, Vol. II, p. 514, cited by Naess.) Again, although Bohr's theory, taken strictly, dealt only with the hydrogen atom, it was realized very early on that its applicability to other atoms would be a proper test of its validity. (Cf. also Lakatos, 1970, pp. 140ft., 156, 168-72.) Such examples abound throughout the history of the natural sciences. One need think only of the differing versions of the wave (particle) theory of light, the fluid (kinetic) theory of heat, the Darwinian theory of evolution, the theory of the conditioned reflex, etc. to realize how pervasively we reidentify 'the same' theory in different, conflicting versions. None of this would make sense unless we used the term 'theory' (in a context like 'Bohr's theory of the hydrogen atom' or 'Darwin's theory of evolution') in a loose enough way to prevent the term from being tied to a specific formulation or version of the theory. Specific versions of a given theory must contain some element - presumably their leading ideas - enabling us to reidentify 'the same' theory in different versions in a manner which is not entirely arbitrary. tl Nor will this be an easy task. Consider the variety of formulations of Newtonian mechanics - including Hamiltonian, Hertzian, and Jacobian formulations to cite but a few - and ask yourself whether a detailed case study will assist or hinder us in drawing clear lines. Consider also David Hull's treatment of Mendelian vs. transmission vs. molecular genetics in his (1974) for another illustration of the complexity of this task. 1~ It must be stressed, though, that it is compatible with this dogma to add that within specific contexts o f inquiry some claims and some observational categories may be so firmly entrenched that no results within that context of inquiry can overturn those claims or that observational category structure. When this caveat has been added, I think the dogma in question is true. The caveat is of fairly broad importance. It may be used, for instance, to support Levi's distinction between 'global' and 'local' logics of induction. 13 Feyerabend's strongest arguments on this topic are not familiar in this country, for they are to be found in his little-known (1960). More accessible examples of such arguments may be found in his (1965a). CT. especially footnotes 8, 9, 23, 24, 115, 122 with their allied texts, pp. 180-181, and Section XV.
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14 I intend to include both inferential roles and applicational criteria (the latter being roughly Sellars's language entry and language departure transitions) in the criteria of identity for conceptual structures• Cf. W. Sellars (1954) and other articles collected in his (1963)• Cf. also his (1965) and (1967). x5 The ceteris paribus clanse marks the fact that these sentences may be inferred from other sentences, may be used in indirect discourse (or in direct discourse in crosslinguistic discussions), etc. It is only in immediate, noninferential application of the sentences that the applicational criterion is relevant. Note that appropriate similarity of occasion may involve linguistic stimuli - for instance when the sentences are uttered in response to a question. 16 To answer this question, one must know both languages. The issue does not concern phonetics or surface syntax and cannot be answered by 'externalist' (e.g. behaviorist) considerations. The attempt to secure translations on an externalist basis will inevitably lead to failure. But this failure (which is approximately equivalent to the insolubility of Quine's problem of the indeterminacy of translation) is an artefact of the needless restriction of one's information. For a similar argument, cf. B. Aune (1967), pp. 56ff. and especially 203ff. 1~ Feyerabend, for example, speaks of German, French, and English as different dialects of the same theory. SeUars, while he does not claim that these languages embody the same conceptual scheme, holds that in translating a foreign language into a familiar one, one interprets the foreign language as embodying (with some distortions) the conceptual scheme of the familiar language. Thus the 'analytical hypotheses' (Quine) which one employs in a coherent system of translation treat the tokens of the foreign language as embodying types which are available in the base language. Sellars and Feyerabend, then, both hold that expressing the same theory (conceptual scheme) involves a network of similarities between the languages and is, strictly speaking, a matter of degree. It is an idealization, therefore, to treat two bits of language as expressing precisely the same theory (conceptual scheme) - an idealization rather similar to the common idealization in (applied) thermodynamics which is made in treating any physical system as thermodynamically closed• This idealization is extremely fruitful. The issue which I raise in the text concerns the appropriateness of extending this idealization to whole languages, and is analogous in interesting ways to the objections occasionally raised in thermodynamics against speaking of the universe as a whole as a dosed system. Cf., e . g . D . W . Theobald (1966), pp. 73-74. 18 There are interesting connections to be explored between these views and the Chomskian claim that all lauman languages have a common depth grammar. Choresky's claim is particularly relevant to the topic of the next note• 19 This position has been staked out for Hopi by Benjamin Lee Whorf (1956), especially the 4th-9th essays. Whorl claims that Hopi is far more relativistic in character than the Newtonian Western. Many people have drawn on (and criticized) Whorf's work in the debate over Quine's thesis of the indeterminacy of translation and Feyerabend's thesis that theories are often incommensurable. 20 This, of course, is above all Feyerabend's position. He holds, e.g., that "Knowledge is not a process that converges toward an ideal view; it is an ever-increasing ocean of [incommensurable] alternatives, each of them forcing the others into greater articulation, all of them contributing, via this process of competition, to the development of our mental faculties." (1965b, pp. 224-225.) 21 Sellars emphasizes a similar point in the course of his argument that theories should •
..
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be conceived more narrowly than conceptual schemes. (Cf. his 1965, esp. pp. 172-4, 187ff. and Section IIL) In part, I seek to reinforce Sellars's distinction between conceptual schemes and theories by articulating certain considerations concerning theories more clearly than he has. On the other hand, I wish to deny the adequacy of his way of delimiting conceptual schemes in terms of languages and their common interlinguistic conceptual structure. Such conceptual structures, like thermodynamically closed systems, are idealizations which (in general) are far better approximated by 'artificial' experimental arrangements (formal languages) than by 'natural' interactive systems (natural languages). 22 In addition to Sellars, ibid., and Naess op. cir., certain views of Mary Hesse and Imre Lakatos concerning the nature of theories are grist for my mill. Apparently Hesse's latest book, which I have just received, is the best source for her views on this topic: el. her (1974). For Lakatos, cf. e.g. his (1970). 23 Following Naess, I would argue that the atomic theory of matter has no hard core, but does have a leading idea. Dalton's, Boltzmann's, and Bohr's different atomic theories of matter are also properly treated as different versions of the atomic theory of matter. Each of these different professional versions of the theory has a Lakatosian hard core - but it is by no means the same hard core. Lakatos, in an interesting passage (1970, pp. 183-4), argues against Popper that the atomic theory of matter should be treated as a 'scientific' rather than a 'metaphysical' research program. This terminological difference seems to me insignificant; in order to preserve the dynamical aspect of theories, Lakatosian hard cores will have to be softened up. They will remain irrefutable, but no well demarcated set of claims will constitute the hard core of a research program. 24 See above, note 10. 25 Recall note 12. I have in mind here such examples as the stagnant ether version of the ether theory of light and the Michelson-Morley experiment. The textbook presentation of this case often suggests that the experiment immediately falsifies the stagnant ether theory. This is, of course, false, as Lorentz's interpretation of the LorentzFitzgerald contraction shows. It might be argued that no 'local' considerations (direct experimentally based arguments within the then-available theoretical context) could decisively refute the stagnant ether version of the ether theory. Yet that theory has been shown to be mistaken as thoroughly as any theory is ever shown to be mistaken. Cf. Lakatos (1970), pp. 159 iT., Holton (1969), and Swenson (1972), and Zahar (1973). 26 Sellars states this second point quite forcefully in his (1965). p. 194, where be distinguishes between "(a) lawlike observation framework counterparts [of theoretical laws] which are compatible with [the available] observational evidence" on the one hand, and "(b) lawlike observation framework counterparts which not only satisfy condition (a), but which were accepted, and would still be accepted, on purely inductive grounds - i.e., in the absence of theoretical considerations." Kepler's laws are an example of (b), while Kepler's laws as corrected by Newtonian perturbation theory are an example of (a). 2v Hesse (1969), Section HI, esp. pp. 99ff. 2s Cf. especially Section IV of his (1961). 29 When I say that a theory is applied directly to certain entities, I mean that as it is used in the appropriate linguistic community, non-inferential linguistic responses to the world concern the entities in question. As Professor Sellars might put it, the language entry and language departure transitions of the community in question involve sentences of this level. Cf. his (1954).
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30 Cf. Theobald, op. cit., p. 75, for an argtm~ent in support of the view that " a statement of the behavior of molecules individually is not sufficient to derive any statements about the behavior of an ensemble of molecules without additional statistical premises." (Theobald's emphasis.) sl In effect, I am arguing that two dimensions of the polydimensional concept of meaning - the dimension of inferential connection and the dimension of applicational practice - can vary in considerable independence of each other. Overreliance on either dimension in determining meanings can be misleading. Overreliance on the inferential dimension yields radical meaning variance far too easily, while overreliance on the dimension of applicational practice leads to overestimation of the stability of meaning. It would be interesting to connect this approach to the concept of meaning with Putnam's suggestion that there are divisions of labor within the linguistic community in determining meanings. CY. Putnam's (1973a) and (1973b). 32 It is worth adding a cautionary reminder here: The one-tiered character of the theory amounts to a unity of observational and theoretical language. It does not mean that there can be no distinctions of 'level' within the theory. Quantum mechanics, for example, appears to be a theory with internal level divisions such that, for physical reasons, observation sentences could not concern the theoretically basic level. 33 I am using this rubric as is standard in the philosophical literature. There is some reason to doubt whether this usage meshes with a large class of scientific uses of terms like 'reduction' and 'reductive explanation'. Cf. e.g. Nickles (1973). 84 Cf. note 30, above. 35 It is important to realize that some theories cannot conceivably acquire a one-tiered application due to defects in their structure. The Bohr theory of the hydrogen atom, which (as Lakatos correctly argues) has inconsistent foundations, is an example of such a theory. Feyerabend, in (1964), makes an important distinction between local instrumentalism supported by scientific considerations and global instrumentalism supported by philosophical considerations. A theory like the Bohr theory (and, according to Feyerabend, the 'modern' quantum theory as well), cannot serve as an ultimately satisfactory basis for an observation language because of its inconsistent foundations. This result is established by an 'internal' ('scientific') analysis of the theory in complete independence of any general philosophical arguments in favor of a pervasive instrumentalism. The importance of another such instance - the conjunction of Newton's mechanics and Maxwell's electrodynamies also has inconsistent foundations - will be remarked in note 38 and the text thereto. 86 Thanks to many ill-considered popular discussions of Einstein's STR, this claim requires careful formulation. The truth may well be relational (the truth of a claim like ' E l is earlier than E2' may well be reference-frame dependent) without being in any epistemologically noxious sense relative. The terminology of such discussions has been adversely affected by the sad fact that Einstein's original name for STR - namely 'Invariantentheorie' - did not catch on. ~7 To apply the distinction between intra-theoretieal and cross-theoretical explanation, one must first determine how narrowly or broadly to construe the identity of the theory (or theories) in question. At almost every stage oI its development, revisions in a theory may be viewed as having potential for enforcing a change of theory. Although a preliminary judgment of the disruptive potential of a particular revision may be made before the fact (Planck knew immediately that his quantum hypothesis was no ordinary adjustment in attxiliary hypotheses - and he disliked it from the first), the ultimate effect of a suggested revision in an historical case can only be judged post hoc.
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One consequence of this result is that Kuhn's 'normal science' becomes implausible as an account of normal science. In the context of discovery, almost all serious theoretical work has significant revolutionary potential. My thanks to Ray Jackendoff for suggesting this footnote and a portion of the accompanying text. 88 Cf. the essays collected in the section on relativity theory in G. Holton (1973), and especially Holton's (1969). Zahar, however, argues (I believe mistakenly) in his (1973) that Lorentz could solve the foundational difficulties without recourse to the STR. 39 This suggests that Schaffner is right in requiring a successful theory to produce a 'corrected version' of the theories it replaces, but that he may be wrong in requiring the corrected version to be strongly analogous to its original. (All it must preserve is the empirical success of that original plus as much of the categorial scheme of that original as has been absorbed into the observation language.) For example, the corrected version of the caloric theory of heat which the kinetic theory of heat yields must provide (corrected) formulae of heat flow, adiabatic expansion, etc., etc., but it need not involve any adoption of the analogy between the quantity o f heat and the quantity o f a fluid. Nor, on my account, need the association between the primitive terms of the corrected theory and the correlated terms of the reducing theory be one of referential identity as Schaffner requires. This second disagreement with Schaffner may, however, be an artefact of differences between his and my approach to reference. Cf. K. Schaffner (1967) and the treatment of Schaffner by D. Hull, op. tit., pp. 32ff. 40 Consider how long the kinetic theory would require us to wait if we wished to have a reasonable chance of observing the undisturbed waters of a tepid bath separate into a freezing and a boiling portion. BIBLIOGRAPHY d'Abro, A., 1951, The Rise o f the New Physics, Dover, New York. Achinstein, P., 1964, 'On the Meaning of Scientific Temas', Journal o f Philosophy 61 (1964), 497-509. Achinstein, P., 1968, Concepts o f Science, Johns Hopkins Press, Baltimore. Achinstein, P. and Barker, S. (eds.), 1969, The Legacy o f Logical Positivism, Johns Hopkins Press, Baltimore. Aune, B., 1967, Knowledge, Mind, and Nature, Random House, New York. Bunge, M. (ed.), 1964, The Critical Approach to Science and Philosophy, Free Press of Glencoe, New York. Burian, R., 1971, Scientific Realism, Commensurability, and Conceptual Change: A Critique of Paul Feyerabend's Philosophy of Science, Unpublished Ph.D. dissertation, University of Pittsburgh. Child, J., 1971, 'On the Theoretical Dependence of Correspondence Postulates', Philosophy o f Science 38 (1971), 170-77. Cohen, R. and Wartofsky, M. (eds.), 1965, Boston Studies in the Philosophy o f Science, Vol. II, Humanities Press, New York. Colodny, R. (ed.), 1965, Beyond the Edge o f Certainty, Prentice Hall, Englewood Cliffs, N.J. Coloduy, R. (ed.), 1966, Mind and Cosmos, University of Pittsburgh Press, Pittsburgh. Feigl, H. and Maxwell, G. (eds.), 1961, Current Issues in the Philosophy of Science, Holt, Rinehart and Winston, New York. Feigl, H. and Maxwell, G. (eds.), 1962, Minnesota Studies in the Philosophy o f Science, Vol. III, University of Minnesota Press, Minneapolis.
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