Re-orienting discussions of scientific explanation: A functional perspective

Studies in History and Philosophy of Science xxx (2015) 1e9

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Re-orienting discussions of scientific explanation: A functional perspective Andrea I. Woody Department of Philosophy, University of Washington, Box 353350, Seattle, WA 98195, USA

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Philosophy of science offers a rich lineage of analysis concerning the nature of scientific explanation, but the vast majority of this work, aiming to provide an analysis of the relation that binds a given explanans to its corresponding explanandum, presumes the proper analytic focus rests at the level of individual explanations. There are, however, other questions we could ask about explanation in science, such as: What role(s) does explanatory practice play in science? Shifting focus away from explanations, as achievements, toward explaining, as a coordinated activity of communities, the functional perspective aims to reveal how the practice of explanatory discourse functions within scientific communities given their more comprehensive aims and practices. In this paper, I outline the functional perspective, argue that taking the functional perspective can reveal important methodological roles for explanation in science, and consequently, that beginning here provides resources for developing more adequate responses to traditional concerns. In particular, through an examination of the ideal gas law, I emphasize the normative status of explanations within scientific communities and discuss how such status underwrites a compelling rationale for explanatory power as a theoretical virtue. Ó 2015 Elsevier Ltd. All rights reserved.

Keywords: Explanation; Explanatory power; Functional perspective; Idealization; Ideal gas law

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1. Questions concerning explanation and a brief analysis of why the common starting point has run aground Since the middle of the last century, the vast majority of philosophical literature on scientific explanation has addressed a single question and more importantly, interpreted that question in a particular way. Philosophers have asked, “What is the nature of scientific explanation?” and assumed that an appropriate response would provide an analysis of the relation that binds a given explanans to its corresponding explanandum. Such analyses presume the proper analytic focus rests at the level of individual explanations, and that these are to be analyzed predominantly in syntactic and semantic terms. Inferential, causal (including process-based, kairetic, counterfactual, and mechanistic variants), and erotetic accounts each provide a direct characterization of individual explanations (Hempel & Oppenheim, 1965; Hempel, 1965a; Salmon, 1984; Strevens, 2008; Woodward, 2003; Van Fraassen, 1980). The unification account concerns itself, somewhat E-mail address: [email protected].

differently, with determining the overarching theoretical system that is most unifying and, as a consequence, confers explanatory status on the explanations provided by that structure (Friedman, 1974; Kitcher, 1989). Yet even Kitcher’s account places emphasis on the structure of individual explanations, through its characterization of argument patterns (Kitcher, 1989).1 There are other questions we could ask about explanation in science, questions that are equally important to consider though they have received much less philosophical attention. Consider, for instance, the following three questions (and presumably there are others): 1. What are the adequacy conditions for individual scientific explanations? 2. How should explanatory power be justified as a theoretical virtue, if indeed it should be? 3. What role(s) does explanation play in science? 1 Even so, Kitcher’s account stands perhaps closest in spirit to my suggestion here.

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These are distinct questions, and each is intuitively meaningful (though admittedly vague as stated). Even so, we could expect that any response to one might well place constraints on acceptable responses to the others. One persistent weakness of the explanation literature, to my mind, is how seldom the interconnected nature of these issues is acknowledged. As noted earlier, most attention has been given to the first question, rendered in terms of the explanans-explanandum relation, with an implicit assumption that this is the primary focus of concern.2 Meanwhile an assumption that explanatory power is indeed a theoretical virtue and a justified factor in theory choice is so pervasive that the second question may hardly seem to require explicit argument. Yet debates about the legitimacy of inference to the best explanation appear to be the only discourse that outlines more explicitly how the justification of explanatory power is supposed to run, and the results are highly contentious. The third question, in contrast, seems rarely articulated. While Hempel’s (1965a) reasons for grappling with the first question in the ways I have described are clear enough, it is less obvious why most others have followed the same path. Perhaps philosophers within this tradition have been grappling, in effect, with the nature of explanation simpliciter. Science provides the epistemic warrant for the information provided in an explanation, but the explanation itself is not so much a scientific explanation as it is the explanation. The focus, in other words, has been on what makes some scientific information explanatory rather than on what makes some explanations scientific or what characteristics might be distinctive of explanation in science. Yet irrespective of the exact aim behind the general project, each traditional account (nomological, causal, unificationist, pragmatic) draws on core intuitions to offer its own characterization. The intuitions grounding each account are distinct, however, thereby exposing the most persistent problem in this lineage of philosophical analysis: the explanations that are generated and endorsed across modern scientific communities are diverse and pluralistic, rather than homogeneous, in kind. An account of the features of individual explanations that is both rich in detail and genuinely unified would seem to be out of reach. It simply would not fit the multiplicity of practices we observe. Analysis that begins with the first question, taken in isolation, can slide too easily into unwarranted essentialism about the nature of explanations across the sciences. Consequently such analyses must declare whole categories of explanations tendered by practitioners illegitimate or inadequate. There are methodological problems as well. The participants in these philosophical debates have quarreled famously over a set of reputed, but still disputed, “counter-examples”: the flagpole and the shadow, the ink spill on the carpet, leukemia and radiation exposure, and hexed salt (to name just a few). But the dispute cannot possibly be settled in this manner. The counterexamples themselves rely necessarily on the very intuitions that serve as foundation for the original disparity of viewpoints. The person challenged with a counterexample can always insist it is not a successful explanation; meanwhile, an individual upholding the counterexample’s legitimacy has only further intuitions to ground her dissatisfaction. The likely outcome, of course, is a stalemate.

2 For a different analysis that nevertheless seems consonant with the view presented here, see Love’s (2012) discussion of formal and material methodologies within the philosophy of science. This framework provides a useful means of grappling with how the issues raised here with respect to explanation may have counterparts in other traditional philosophical subjects ranging from induction to the structure of theories or even discovery.

2. Changing the question: the functional perspective I’d like to approach things somewhat differently, by beginning with the third question. What role or roles does explanation play in science? Turning our attention to the role(s) played by explanation in science compels, effectively, a functional analysis of exactly the sort delineated, for different purposes, by Hempel (1965b), himself drawing on the work of Merton (1957): The kind of phenomenon that a functional analysis is invoked to explain is typically some recurrent activity or some pattern of behavior. And the principle objective of the analysis is to exhibit the contribution which the behavior pattern makes to the preservation or the development of the individual or the group in which it occurs. Thus, functional analysis seeks to understand a behavior pattern or a sociocultural institution by determining the role it plays in keeping the given system in proper working order. (Hempel, 1965b, 304e05). This description suggests an important respect in which my third question, as originally expressed, harbors vagueness that should now be clarified. The notion of functional analysis borrowed from sociology applies to “recurrent activity” or “some pattern of behavior”. Likewise, the question at hand concerns explanation as an activity, or custom, of scientific communities, rather than the propositional content produced as a result.3 Explanation as activity involves a request for information and a response. It is a practice embedded in language and representation; it is discursive.4 Thus, the question being considered can be stated more precisely as “What role does explanatory discourse, and explanatory activity more generally, play in the practice of science?” What I label the functional perspective aims to reveal how the practice of explanatory discourse functions within scientific communities given their more comprehensive sets of aims and practices. In comparison to traditional accounts of scientific explanation, there is a shift in focus away from explanations, as achievements, toward explaining, as a coordinated activity of communities. On first consideration, it may seem there is nothing interesting for a functional analysis to reveal. It is commonly assumed that explanation is a central, indeed perhaps the paramount, aim of modern science: It is the desire for explanations which are at once systematic and controllable by factual evidence that generates science; and it is the organization and classification of knowledge on the basis of explanatory principles that is the distinctive goal of the sciences (Nagel, 1961, 4). According to this stance, explanatory desires are the starting point; we engage in science precisely because it helps us to understand the world around us. Notice that such a view treats explanations precisely as achievements, as the sorts of things for which one reasonably could aim. And even if we accept this view regarding the overarching aims of science (and we need not), the value of assuming a functional perspective does not evaporate, because acknowledging explanatory desires in no way determines what counts as explanatory for a scientific community.

3 Kitcher also initially identifies explanation as an activity but then turns quickly to discussion of arguments, which he characterizes in terms of premises, conclusions, and the connection between them. He thereafter shifts focus to the following question: “What features should a scientific argument have if it is to serve as the basis for an act of explanation?” (Kitcher, 1981, 510). In this regard, he never grapples directly with the nature of the activity itself. 4 This point is stressed in Van Fraassen’s (1980) erotetic account of explanation, framed as it is in terms of the logic of questions.

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There may appear to be a threat of circularity here, suggesting we must answer our first question before approaching the others. If we do not know how to characterize individual explanations, how would we identify them, and consequently how could we hope to determine their function? But the threat is illusory. We routinely identify all sorts of things in our worldepears, weddings, stellar nebulaeewithout having robust analyses of their kinds. In the same vein, in posing this question we set aside, momentarily, the goal of articulating necessary and sufficient conditions for individual explanations, while still assuming that we can identify reliably a considerable range of them. Doing so is no more problematic than it is in everyday life, as long as we do not assume that there is nothing for an analysis of the adequacy conditions for individual explanations to accomplish or no contexts in which such analysis would be necessary. The hope instead is that we can circumvent the stalemate generated by competing intuitions by turning our attention back to scientific practice. The functional perspective reorients our efforts, asking us to think about where and when explanations are sought and formulated, and subsequently to consider what role(s) they might play in practice. With regard to the first piece of this project, I offer five rough generalizations: 1) Explanatory discourse (in contrast to explanations in the abstract) is social in nature. There is always, at least implicitly, a request (question) and a response, and these are typically negotiated or shared among individuals or groups.5 2) Explanations frequently pass between individuals or groups with different levels of expertise. A person requesting an explanation often is not in a good position to judge the adequacy of the response, and must rely on the authority of the responder to accept the explanation as legitimate. 3) At any given time a set of exemplary explanations is shared by most members of a given scientific discipline or sub-discipline. This set does not correspond directly to the phenomena the discipline judges most important to explain.6 4) Explanatory discourse frequently involves articulating communally accepted explanations; it often concerns repetition of known explanations rather than cultivation of novel explanations. 5) Generating and discussing explanations is a central component of science education, occupying significant space in textbooks and time in classrooms. Indeed, it seems fair to conjecture that self-conscious acts of explanation occur most often in educational contexts. I discuss some implications of these generalizations elsewhere, but here I introduce them to initiate consideration of the functions of explanatory discourse. The set is surely incomplete, but if the generalizations are roughly on target, at least some of the functional roles of explanatory discourse emerge rather straightforwardly. Explanatory discourse often involves the communication of exemplary explanations among members of a given scientific community,

5 What about the person who generates an explanatory question and answers it herself? This is certainly possible in principle, but as Salmon (1998) and Van Fraassen (1980) both discuss, explanatory demands would not arise for an omniscient being. Explanations arise from ignorance, or at the very least, uncertainty. Consequently, for the individual to pose a genuine explanation-seeking question, even to herself, she must not already know the answer and will turn to some external source of information, one she considers authoritative, to find the answer. In doing so, she is engaged in an activity that I would argue is inherently social, because the sorts of authority required to ground the status of any information on which she comes to rely must derive, in part, from social relations. 6 It may however be linked in systematic, but less direct, ways to such phenomena.

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and one aim of explanatory practice seems to be training novice practitioners to recognize typical explanatory patterns. Elsewhere I have argued that scientific disciplines and subdisciplines are largely delineated by the explanatory patterns they embrace (Woody, 2003). The history of science, meanwhile, provides rich empirical support for the claim that production of explanations serves to constitute, rather than merely communicate, “intelligibility” for a scientific discipline (see especially Dear (2006)). Precisely because explanatory discourse inculcates particular patterns of reasoning, it functions to sculpt and subsequently perpetuate communal norms of intelligibility. In effect, explanations encode the aims and values of particular scientific communities, telling practitioners what they should want to know about the world and how they should reason to get there. Cartwright (1983) points to something like this picture while discussing ceteris paribus laws in the physical sciences. She asks “Why do we keep Snell’s law on the books when we both know it to be false and have a more accurate refinement available?” (Cartwright, 1983, 47). We could ask the same question about a plethora of convenient fictions: the ideal gas law, generalizations derived from Mendelian genetics, motion along frictionless surfaces, infinite potential energy wells, etc. Cartwright asserts: . [the] reasons have to do with the task of explaining. Specifying which factors are explanatorily relevant to which others is a job done by science over and above the job of laying out the laws of nature. we have to decide what kinds of factors can be cited in explanations. One thing that ceteris paribus laws do is to express our explanatory commitments. They tell what kinds of explanations are permitted. (Cartwright, 1983, 47e48, emphasis added) In other words, while descriptive accuracy of certain sorts may well be necessary for explanation, it is not sufficient. Moreover, what sorts of accuracy are necessary arguably varies in accordance with judgments of explanatory relevance (just as variance across scientific practices and philosophical intuitions suggests).7 But admitting even this much brings the social normativity of explanation to the surface. Explanatory commitments are not, at their foundation, commitments of individuals; they are commitments of communities. Relevance is stipulated based on communal norms. As a consequence, individual scientists rarely make independent decisions regarding explanatory relevance; with proper training, they can make reliable judgments regarding what is relevant and what is not, but this is primarily a matter of recognition, after social conditioning, rather than independent determination. If I am correct about this, we should ask a further question. Do shared norms of intelligibility (and explanatory relevance) support proper functioning of science? Does explanatory discourse, in other words, have a methodological role to play in science? Contrary to the charge of pernicious groupthink often leveled at Kuhnian normal science, the case is not hard to make. The conditions of contemporary science, including the advent of ‘big science’ in which large groups of scientists coordinate their labor to conduct research, often within elaborate institutional structures, as well as increased globalization, necessitate that practitioners communicate reliably across wide geographic, social, and cultural distances. Increasingly sophisticated instrumentation and techniques for

7 No doubt some philosophers would not agree with the supposition here that explanatory relevance is based in part on decision. There is a rich literature addressing the thorny issue of explanatory relevance. It is a core element of Van Fraassen’s (1980) erotetic account, a central concern for both Kitcher’s (1989) unification account and Hempel’s (1965a) inductive-statistical model, and one source of Hempel’s infamous footnote 33 problem.

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analysis produce ever more complex and rich sets of data, while the expertise required to use these material and intellectual tools generates pressure for specialization among practitioners. Under such conditions, maintaining the coherence of scientific activity becomes a central challenge, and meeting the challenge requires exploiting distinct disciplines and sub-disciplines while placing constraints on their potential divergence. The actions, aims, and assumptions of communities of practitioners must be robustly coordinated and aligned. Explanatory discourse is one tool, among others, used to meet this challenge; in this respect, explanatory discourse is crucial for the formation of cohesive scientific disciplines. In general terms, this is one important functional role for explanatory discourse in modern science. 3. An example: the ideal gas law Painting in such broad strokes is suggestive, but a more finegrained analysis requires us to look at particular cases. In other places, I have discussed various examples from the physical sciences (Woody, 2013, 2014). Here I discuss a single case: the ideal gas law in chemistry. My choice is deliberate. Several traditional accounts of explanation either deny the explanatory power of the law or make its explanatory status derivative (Woody, 2013). By arguing that the functional perspective provides a better platform for recognizing the law’s explanatory power in chemistry, I aim to display the framework’s utility. On its surface, the ideal gas law is an equation of state relating three variables that correspond to measurable properties of actual gases: pressure, volume, and temperature. In this regard it looks like a straightforward law of co-existence, with clean predictive power, of exactly the sort endorsed by Hempel’s conception of explanation as nomological subsumption. But the law is also a ceteris paribus law subject to the dilemma Cartwright (1983) posed for Hempel’s account: interpreted literally, the law is either false or applies to no actual gases, depending on whether we explicitly articulate the ceteris paribus clause, which would restrict it to gases in the limit of zero pressure. An alternative is to treat the law as a (mere) phenomenological approximation. It does describe with reasonable accuracy the behavior of actual gases with temperatures well above their condensation points and pressures below about one atmosphere (although there are exceptions even within this range). In practice, however, application of the law is not limited to those cases in which it provides roughly accurate empirical descriptions. Consequently, treating pV ¼ nRT as an approximation of the quantitative relations that obtain between actual gas properties provides few resources for making sense of the scope and frequency of the law’s use. Descriptions surrounding application of the law, in textbooks and classrooms, suggest instead that idealization underwrites both its broad application and its explanatory status. An ideal gas, essentially particulate in nature, being composed of small, extremely dense particles that exert negligible forces on one another by virtue of large average separation distances, would be perfectly represented by pV ¼ nRT. This vision guides model construction for actual gases, and when the law poorly approximates actual gas behavior, properties are conceptualized as deviations from the ideal. In this way, the law’s mathematical structure provides inferential scaffolding for the treatment of all gases, not only those for which it is a good approximation. Thus, the ideal gas law’s role in practice is not essentially descriptive, but rather prescriptive; by providing selective attention to, and simplified treatment of, certain gas properties (and their relations) and ignoring other aspects of actual gas phenomena, the ideal gas law effectively instructs chemists in how to think about gases as they are characterized within chemistry.

Idealization also facilitates theoretical connections between descriptions of macroscopic properties and descriptions of molecular systems. The “zero pressure” limit of an ideal gas links directly to the theoretical assumption that gas particles exert no forces on each other, while the assumption that zero pressure is achieved by large separation distances suggests modeling the system as a collection of Newtonian point masses undergoing elastic collisions only with the container. The Newtonian model, in turn, provides explicit guidance for modifications of the law when greater phenomenological accuracy is required. For example, reasoning about hypothetical particle interactions drives the van der Waals equation8 to incorporate parameters representing particle volume as well as pair-wise particle attractions (see Mahan, 1975, 67e72). The law even performs crucial conceptual work, by laying foundation for the concept of ‘temperature’. While the subjective, inherently comparative, quality of human perception of heat prevents perceptual experience from grounding a coherent quantitative concept of temperature, the ideal gas law’s stipulation of a linear relationship between volume and temperature asserts a partial definition of what temperature is: namely a property that under constant pressure varies directly, and precisely, with gas volume. In addition, deriving the law from a Newtonian model furthers conceptual articulation by identifying temperature with the average kinetic energy of gas molecules. In these regards the law imposes structure on an empirical domain rather than passively describes it. In sum, the ideal gas law provides scaffolding for reasoning about gas behavior, it facilitates the theoretical unification of macro and micro level descriptions, and it grounds our understanding of core concepts such as temperature. These points all concern the law’s cognitive role in chemistry, and although I have outlined the points one by one, they are heavily intertwined in practice, as the following quote from a college-level textbook displays well: By pursuing the mathematical consequence of the fact that a gas consists of a large number of particles that collide with the walls of a containing vessel, it is possible to derive [the] law, and to gain a more thorough understanding of the concept of temperature. By trying to account for the failure of gases to obey [the] law exactly, we can learn about the size of molecules and the forces that they exert on each other. Thus, the study of this simplest state of matter can introduce us to some of the most universally useful concepts of physical science (Mahan, 1975, 33). Much of the law’s value derives from the complex inferential connections it enables, but this fact is visible only through attention to when and how the law is actually used. There is a further point, one based more firmly in practice, which also merits notice. Discussion of the ideal gas law occupies the first substantive chapter in almost all standard texts of general chemistry, following right after consideration of stoichiometric relations. On initial consideration, this ordering can appear perplexing, or perhaps even misguided. One could argue that the study of gases is a marginal topic for contemporary chemistry and even less obviously an appropriate place to begin a pedagogical discussion. After all, students have few intuitions regarding gas behavior, patterns in that behavior are seldom observable outside controlled conditions, and obtaining such control is no easy task for a rudimentary classroom lab. Why not start with stuff students can hold in their hands (or at least in a test tube)? Is there a compelling rationale for beginning with gases? Indeed there is. These initial discussions function not only to provide information regarding the behavior of gases but also to orient the entire field of chemistry, both conceptually and methodologically.

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Van der Waals equation: ðp þ an2 =V 2 ÞðV  nbÞ ¼ nRT

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The ideal gas law serves as a bridge between the realm of bulk substances, the traditional subject matter of chemistry, and the realm of atoms and molecules, the discipline’s endorsed theoretical framework. It provides, moreover, a concrete example of how these two realms should be joined through mathematical scaffolding. Treating gases as collections of particles underscores the centrality of the atomic theory for chemistry, and at the same time, it endorses a Newtonian paradigm of analysis by conceiving of gas particles as point masses subject to classical forces. Studying the ideal gas law helps the novice to understand gas behavior, and perhaps more importantly, helps her to understand the discipline of chemistry. Notice how little has been said about individual explanations. Applications of the ideal gas law are simple algebraic exercises; focusing on them would reveal little about how the ideal gas law functions and why we continue to employ it in explanatory contexts. When to apply the law, what to amend when the law is insufficiently accurate, and how the law informs general understanding both of what a gas is and how it should be differentiated from other material statesdthese matters are less straightforward but also more central to the law’s explanatory status. Why do explanations invoking the ideal gas law remain common in chemistry? In essence, explanatory discourse involving the ideal gas law displays an ideal of intelligibility for chemistry. The law unifies treatment of actual gases through selective attention to core properties, effectively declaring which properties are relevant in chemical contexts. It builds bridges between different levels of theory, and it provides some general methodological directives regarding the proper role of theory within chemistry. In all these ways, the law provides regulative guidance.9 From the functional perspective, this is the source of the law’s substantial explanatory power, but the point is visible only through attention to explanatory practice. 4. Challenges and virtues of adopting the functional perspective Having looked at an example in some detail, I now want to consider the viability of the functional perspective more generally. But how are we to evaluate it? Once again, I turn to Hempel’s earlier discussion of functional analysis to set the stage: [functional analysis] is best viewed not as a body of doctrine or theory advancing tremendously general principles. but rather as a program for research. expressing a directive for inquiry, namely to search for specific self-regulatory aspects of social and other systems and to examine the ways in which various traits of a system might contribute to its particular mode of selfregulation (Hempel, 1965b, 329). I first consider a set of challenges to the utility of the functional perspective before turning to its virtues. 4.1. Challenges 1. Even from our cursory discussion of the ideal gas law, one might worry that the specificity required to characterize different scientific communities, their aims, and their practices offers so little in the way of generalization that the framework offered by the functional

9 This analysis resonates with a more general discussion found in Teller (2004) in which Teller argues that ceteris paribus generalizations typically function as practical guides for theory application with their use thoroughly grounded in procedural knowledge. This claim is embedded in Teller’s overarching view that “characterization of science in terms of [universal] laws is itself an idealization” (Teller, 2004, 731). I am generally quite sympathetic to this view.

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perspective can do no philosophical work. Such concerns are surely appropriate but the diagnosis, it seems to me, is incorrect. While the functional perspective readily acknowledges the possibility that different communities have significantly different explanatory patterns and practices, this flexibility appears well suited to accommodate the diversity of explanations we confront in practice. But not anything goes. First, this account assumes that within communities, there is common structure among accepted explanations. Heterogeneity may appear across practices but should not be expected to occur routinely within them. Furthermore, embedding and bridging relations between scientific communities and sub-communities will place substantial constraints on the explanatory diversity that can be accommodated across them. The fact that communities must interact and work together entails that their models of intelligibility must be generally commensurable. (Contemporary biochemistry and molecular biology provide a useful example here; see Morange, 2012.) Whenever practitioners offer candidate explanations that diverge from endorsed patterns, perhaps as a result of interdisciplinary contexts, we should anticipate a process of initial resistance, increased scrutiny, and in some instances, subsequent negotiation. 2. Even so, does the functional perspective provide no platform for judging the adequacy of any given explanation or explanatory practice beyond whether it conforms to particular social norms, i.e. whether it fits the endorsed pattern? To the contrary, one of the real virtues of the functional perspective is that it provides a framework for judgments regarding the appropriateness of particular explanatory patterns by assessing the fit between patterns and goals. To be more specific, it underwrites normative judgments based on whether a given pattern or model of intelligibility is well suited to support the cognitive and epistemic aims of the respective scientific community, and in turn whether a given explanation exemplifies this pattern or model. Mechanistic explanations, for instance, are ill suited to both the theoretical foundation and the predictive orientation of quantum-theoretic scientific practice. On the other hand, certain types of mechanistic reasoning are central to the synthetic goals of organic chemistry, providing substantial reason to maintain explanations invoking reaction mechanisms in this domain (see, for example, Goodwin, 2007). But the adequacy of particular explanations does remain inherently contextual from the functional perspective (in much the way Van Fraassen (1980) has argued). 3. There is another worry. Can this framework accommodate cases where the aims of individuals or even whole scientific communities are themselves taken to be explanatory? I take this challenge to be closely related to the position addressed earlier with respect to Nagel (in Section 2), and here I develop in a bit more detail the line of reasoning sketched there. The project motivating the functional perspective focuses on explanatory practice and suggests that what counts as explanatory will depend on the overarching aims of a given community. Only if a community had nothing but explanatory aims would there be any conceptual threat of circularity, and I do not take such a case to be typical of the modern sciences. Furthermore, we should take seriously the possibility that talk of “explanatory aims” is best conceived as code for any among a wide ranging set of more specific virtues that scientific communities embrace for their theories and the practices that utilize them. In other words, we will hear talk of explanatory aims precisely when a community has decided upon and endorsed particular norms regarding how to response to explanatory requests. To have explanatory aims is then simply to desire to be able to answer explanatory why questions in ways consistent with such norms (and this in turn motivates the desire to accurately describe these norms, without which we would have no sense of what explanation means for a given scientific community). 4. But what story are we now to tell about noteworthy singular explanations? Can these be, in and of themselves, significant

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intellectual and scientific achievements? Or are they all simply exercises in conditioned mimicry? Here the scope of my project should be held in mind. The aim is to consider explaining as an activity within communities, and this activity does, I believe, exhibit robust evidence of strong explanatory norms. Yet this in no way undercuts the possibility of particular explanations being more significant achievements than others and some generating deep insight. Even so, I would suggest that appreciating the significance of particular explanations necessitates coming to terms with the general practices of which it must, in large part, be a result. 5. Finally, someone will surely object, “How can this account differentiate between genuine explanations and those merely accepted as such?” I take this to be a question of metaphysicseone requesting an account of explanation simplicitereand thus strictly outside the scope of the project at hand. Even so, I cannot imagine how we could ground “genuine” except by appeal to our very best science. To avoid begging the question we must not assume there to be a unique set of objective, two-place relations that determines which facts in the world explain which other facts (and this holds even if there are objective causal structures). Turning to practiceein a sense both descriptive and socialesuggests a different orientation: certain pieces of information provide the scaffolding required to participate in scientific investigation of this world in productive ways. But science is monolithic neither in its aims nor its practices, and thus, different sorts of claims may indeed be explanatory in different scientific contexts. To label something an explanation is not to identify it as a particular sort of descriptive information, but rather to endorse it, to suggest that it provides the right way to think about things, relative to certain (often implicit) aims. Wellestablished explanatory patterns hold such honorific status and function as exemplars of reasoning that bind practitioners together in ways that cultivate and support the social coherence and productivity of particular scientific endeavors. What I suspect to be the same cluster of concerns may be articulated in a slightly different manner: Does this account potentially fit explanatory practices outside of science, and if so, how do we guard against a view that lumps scientific explanation with explanations in contexts as far ranging as astrology or creationism? Delineating the domain of application for the functional perspective is beyond the scope of this essay, but I do not assume, as a starting assumption, that the general framework provided here need be exclusive to science. To the contrary, this framework meshes well with recent research within sociology on explanatory practices in a wide variety of contexts (Tilly, 2006). This is not surprising, and more importantly, it underscores that issues of demarcation, to the extent that they have satisfying answers, are not to be resolved solely, or even primarily, by appeal to the explanatory practices of science. It is highly possible that the actual norms endorsed by well functioning scientific communities will be evidence-based and epistemically respectable in ways that differentiate scientific explanations from those tendered in other contexts. But such differences will emerge in the explanations themselves, or the information to which they appeal, rather than the practices that recognize, communicate, and perpetuate them. Explanatory practice should not be expected to solve the demarcation problem. 4.2. Virtues 1. The functional perspective asks us to pay attention to actual scientific practices.10 In particular, it captures the descriptive generalizations that initiated our discussion in Section 2. In doing so,

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Arguably such attention to practice is a virtue in and of itself, but I will not argue the point here.

the functional perspective foregrounds the socially normative status of explanations as well as the regulative role of the discourse that includes them. Explanations are revealed to be a primary means of inculcating shared exemplars that function as norms of intelligibility. In this regard, they enable normal science in very much the Kuhnian senseethrough exemplars and procedural knowledgeeand establish conditions for membership in disciplinary and sub-disciplinary scientific communities (Kuhn, 1962). This accounts for both the prevalence of explanatory discourse in science education and the fact that repetition of known and accepted explanations is often more common than cultivation of novel explanations. 2. As multiple philosophical analyses have underscored, the logic of functional reasoning is slippery precisely because it relies on an inference from the fact that some structures or properties would be sufficient for bringing about a given outcome or state of affairs (when coupled with the existence of those outcomes or states of affairs) to the assumption that those structures or properties have indeed played such a role. Yet the possibility of functional equivalents makes it hard to determine in what contexts such an inference should be reliable. This very characteristic, however, while often seen as the fatal flaw of functional analysis, allows the functional perspective to avoid a common trap in the explanation literature: Precisely because functional analysis requires consideration of functional equivalents, its pragmatic orientation steers us away from an essentialism about scientific explanation that commonly underwrites the desire for a universal model of either explanatory form or content. Given the variety of apparent explanations observed in contemporary scientific practice, as well as the persistence of diverse philosophical accounts of explanation, I take the potential accommodation of explanatory pluralism to be a virtue of this perspective. The functional perspective, moreover, is not merely consistent with explanatory pluralism. It provides reasons why pluralism is unsurprising, and also, by underscoring the multiplicity of scientific aims, a framework for considering the conditions under which pluralism is to be preferred.11 At the same time, pluralism is neither blindly accepted nor endorsed. The functional perspective carries an implicit responsibility to pay close attention to actual practices (a requirement of descriptive adequacy) and provide specific rationales for the endorsement of all explanatory patterns, whether unified or diverse. 3. In part by embracing the possibility of pluralism, the functional perspective also deflects general worries about the explanatory status of models while offering resources to reorient the intense debate regarding whether false models can explain (Bokulich, 2009, 2011; Elgin, 2009). Idealization, abstraction, and other forms of simplification that generate theoretical fictions are easily accommodated to the extent (but only to the extent) that such representations hold genuine utility for the articulated epistemic aims of particular scientific communities (for a similar perspective, see Elgin, 2004). We keep Snell’s law, the ideal gas law, and countless others, ‘on the books’ because thinking in terms of the idealizations they provide has utility with respect to the aims of the relevant communities. This in turn is what makes them explanatory. More generally, the functional perspective suggests a larger story concerning why a great deal of explanatory work is model-based. It is a story about how forms of simplification, compositionality, and even fictionality facilitate portable templates for reasoning, but I will not pursue the details here.

11 In much the same spirit, Love (2013) presents a view of theory in biology that also highlights pluralism as a consequence of the fit between presentations of theory and particular epistemic aims, which he takes to be heterogeneous.

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4. Although in certain respects the functional perspective reorients standard discussions, it still allows us to salvage significant insights from the existing philosophical literature, often by recasting their significance:  A distinctive aspect, and primary virtue, of unification accounts of explanation is that they consider scientific understanding to be global rather than local or particular in kind and take the explanatory status of theoretical frameworks to be a consequence of the unification they supply (Friedman, 1974; Kitcher, 1989). These accounts fit well the many cases in which scientific communities prefer overarching theoretical structures that unify a broad range of phenomena. But unification accounts tend to stumble on how one might justify such a preference, raising worries about metaphysical assumptions of an orderly universe. The functional perspective reveals this preference to be built instead on the conditions for coherent cognitive labor; the justification is methodological in kind and reflects the nature of coordinated intellectual work rather than the nature of the phenomena of study.  Several otherwise quite different accounts (including those of Hempel & Oppenheim, 1965; Hempel, 1965a; Kitcher, 1989; and Friedman, 1974) consider individual explanations essentially to be or to involve arguments (in the formal sense). If, as the functional perspective suggests, explanations serve as intellectual binding for communities, then the centrality of argumentation, often explicitly rendered, is easily understood.  Hempel’s (1965a) inferential account of explanation stresses the connection between explanation and expectation, grounding it in the formal inferential structure of the DN and IS models. Emphasis on the inferential leaves the account vulnerable to a variety of problems, especially those related to explanatory asymmetry and irrelevance. The functional perspective also has a story to tell about why explanation and expectation are often conjoined, but here the narrative turns on the cognitive consequences of social conditioning in light of particular epistemic aims. Such a story can avoid the problems of asymmetry and irrelevance.12  Van Fraassen’s (1980) erotetic account stresses the role of context in determining which factors will be salient for a given explanatory request, but it offers little guidance regarding what aspects of context legitimately influence the adequacy of scientific explanations. The functional perspective provides some means to filter relevant from irrelevant aspects of context by appeal, first, to the aims of the given community constructing or making use of the explanation, and second, to the aspects of context that members of a specific scientific community have been conditioned to accept as relevant. While Van Fraassen’s account highlights the contextual nature of explanation, the functional perspective underscores the essential role of community norms in determining which aspects of context are judged relevant. It also supplies rudimentary structure, through appeal to a given community’s epistemic aims, for philosophical analysis of whether particular norms are indeed appropriate.  Woodward’s (2003) emphasis on manipulability, potential intervention, and the role of explanation in addressing “what if things had been different” questions, is captured by the normative function of scientific explanation from the functional

12 The functional perspective will avoid the problem of irrelevance in ways somewhat analogous to the strategy employed by Kitcher (1989) for his unification account.

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perspective. If explanatory discourse serves to condition the cognition of communities in ways that can direct and support coherent research, that is, if explanations function as prescriptive exemplars (in something like the Kuhnian sense), then it is clear why being able to answer a wide range of “what if things had been different” questions is valuable and why theoretical frameworks that can do so would be judged explanatorily powerful. 5. The functional perspective connects explanation with understanding without undercutting the epistemic significance of explanation. Understanding, in the respect appropriate for modern science, is not narrowly psychological, and thus neither idiosyncratic nor straightforwardly subjective, but instead social and cognitive in complex, interdependent, ways. Explanations must be minimally intelligible to be accepted by individuals. But explanations, especially in educational contexts, condition reasoning, and thus sculpt social norms of intelligibility. Explanations intelligible to members of one community are frequently opaque to outsiders, even other scientists. In this respect, the functional perspective stands in relation to recent scholarship on understanding (De Regt, 2009; Elgin, 2007, 2009; Khalifa, 2012; Kvanvig, 2003; Mizrahi, 2012; Schurz & Lambert, 1994; Trout, 2002), some of which even appeals to the ideal gas law as a central example. Trout denounces much contemporary work on scientific understanding because of what he sees as its psychologistic orientation. He states: “If explanation is to be of value, it must derive its value from its systematic tendency to produce increasingly accurate theories” (Trout, 2002, 230). The functional perspective supplies one means of meeting this challenge without releasing the tight connection between explanation and understanding. 6. Perhaps most importantly, the functional perspective turns our attention to issues of social epistemology by stressing ways in which knowledge production in the modern sciences is deeply, and inherently, social. These include social mechanisms, enabled by institutional structures for science education, for enculturation of new members and the perpetuation of community norms. More specifically, this account of explanatory norms, if correct, may impact current discussions of the role of group acceptance in science and how best to conceive of it (Andersen, 2010; Gilbert, 2000; Wray, 2001). For instance, if explanatory norms were coherent and robust within a given community (whether a particular research group or an international sub-discipline), certain forms of disagreement may seem less likely than if the group were composed of individuals with effectively independent intellectual trajectories. At a minimum, a robust set of shared assumptions regarding what sorts of information or argument provide explanation of phenomena in an empirical domain will influence any process of negotiation. The functional perspective likewise provides some resources for understanding the distinct dynamics of inter-disciplinary versus intra-disciplinary disputes regarding whether a given phenomenon needs explanation and if so, what would be required. At the same time, it highlights the deliberate cultivation of (explanatory) expertise and skill and situates this expertise in relation to the social recognition of cognitive authority and the warranted, and often necessary, role of trust in explanatory practice. As we have already discussed, the functional perspective stresses the contextual nature of explanation, allowing us to see that communities whose epistemic aims differ may embrace distinct sorts of explanatory patterns precisely because different explanatory practices may facilitate coherent and cohesive work in each case. At the same time, conceptual relations as well as relations of dependency among disciplines and sub-disciplines place

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nontrivial constraints on the potential divergence of explanatory patterns. Even practitioners of distinct disciplines frequently share early educational experiences, when initial models of intelligibility are instilled, and they must maintain avenues for meaningful communication during ongoing research. Communities have unique identities but their members also need to work together.

5. Returning to the three questions This is an appropriate point to return briefly to our original three questions concerning explanation: 1. What are the adequacy conditions for individual scientific explanations? 2. How should explanatory power be justified as a theoretical virtue, if indeed it should be? 3. What role(s) does explanation play in science? I have advocated we begin with the third question, interpret ‘explanation’ in terms of explanatory discourse, and adopt the functional perspective. The functional perspective is not intended as a replacement for traditional accounts of scientific explanation, which typically address question one. Even if one adopts the functional perspective, there is still a significant project characterizing the adequacy conditions applied to particular explanations in particular contexts. But can the functional perspective, seen as a response to question three, provide resources for addressing the other questions? While the following remarks are preliminary and would require considerable elaboration to be decisive, I believe they suffice to indicate the potential fruitfulness of integrating discussions of explanation, explanatory power, and explanatory practice. With regard to Question 1: By stressing the functionality of explanatory discourse rather than the syntactic or semantic characteristics of individual explanations, the functional perspective takes a deflationary stance toward question 1 as typically interpreted. By focusing on explanatory practice (including the descriptive generalizations offered earlier), we can recognize as significant the fact that explanation in science involves endorsement. To recognize something as an explanation is implicitly to grant or acknowledge a normative, honorific status. Some explanations, the exemplars, function to actively sculpt and perpetuate norms of intelligibility; others gain their status as explanatory by being related in appropriate ways to the exemplars. (The nature of such relations raises its own set of issues, but these are beyond the scope of the current essay.13) This normativity is what allows explanatory discourse to serve as an enabling condition for coherent practice. But because the epistemic aims of scientific communities are diverse in their specificities, so too are the explanations that help to condition communities to achieve these goals. Thus, there are clear reasons to expect the explanatory diversity we observe. At the same time, explanatory discourse will have a recognizable historical element, because such discourse effectively sets up a feedback loop with regard to assessments of explanatory status. (No doubt consideration of numerous examples will be required to determine whether the observed diversity aligns with epistemic aims in the way this account would suggest.)

13 For example, on this account we would expect to see points of tension in the history of science when certain patterns of explanation that have been embraced by a given community over time come to stand in tension with the current aims of that community but have lingered because of an educational process that continues to reinforce the status of such explanations to young practitioners.

But what about Question 2? If we ask why, other things being equal, we should prefer explanatory theories, there are two common responses: (P1) We prefer explanatory scientific theories because explanation is a central aim of science. (P2) We prefer explanatory scientific theories because explanatory theories are, ceteris paribus, indicative of truth. The first response makes almost tautological the claim that we should prefer explanatory theories, and as a consequence, effectively closes down the request for justification. The second response is rooted in attempts to defend various versions of scientific realism. It condones reliance on inference to the best explanation and effectively takes the explanatory power of a theory as an indicator of its likelihood of being true (though, to be sure, in complicated ways). But the difficulties surrounding IBE inferences are well known, and furthermore, the notion of explanation invoked in such inference patterns seems general and not at all specific to science (which is one reason many classic examples of IBE reasoning involve everyday scenarios rather than scientific ones). For these reasons, it would seem preferable for any justification of explanatory power as a theoretical virtue not to rely on the general adequacy of inference to the best explanation. The functional perspective suggests a different rationale for considering explanatory power to be a theoretical virtue with a warranted role in theory choice. Explanatory theories are ones from which scientists can develop rich explanatory practices that effectively establish communal norms for reasoning that in turn facilitate achievement of the community’s cognitive and epistemic aims.14 According to this suggestion, explanation is genuinely important to the proper functioning of science, but it is a worker bee, rather than (as suggested by P1) a shiny bauble proudly displayed in the aftermath of scientific activity, or (as suggested by P2) a mysterious seer pointing us toward a yet to be discovered truth. 6. Concluding remarks After articulating three questions concerning explanation in science, I have provided reasons why beginning with individual explanations, as the main philosophical tradition does, is problematic. I advocate we start instead with the practice of explaining and adopt the functional perspective. Starting at the descriptive level with particular practices effectively focuses attention on the scientific in scientific explanation, without assuming that we have a freestanding conception of explanation on which to rely. More importantly, the functional perspective suggests that there is a methodological role for explanatory discourse in science. It enforces communal norms regarding what sorts of information are to be considered intelligible and enlightening and the types of reasoning that are legitimate within the community (indeed explanations often display patterns of reasoning explicitly to inculcate them). Consequently, the practice of explanation serves to maintain coherence and cohesion within and across scientific communities. I have confronted, in a preliminary fashion, some challenges faced by the functional perspective and outlined briefly certain assets that I believe accompany this perspective and the methodological rationale it suggests. Finally, I have offered reasons to believe that adopting the functional perspective, by beginning with explanatory practice, puts us in a better position to address the issue of justifying explanatory power as a general theoretical virtue.

14 On some accounts, this methodological role would entail that explanatory power be conceived as an indirect epistemic virtue.

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It is worth underscoring that my suggestions come in two parts: (1) advocacy for adopting the functional perspective, and (2) a specific suggestion regarding what is revealed by this perspective. In principle, one may accept the first suggestion without the second. Moreover, my discussion has focused on a single role for explanatory discourse but makes no assumptions regarding the existence of others. Explanations arise in many scientific contexts, some importantly different than the ones discussed here. We now need to look at a much wider variety of examples to see if this framework is useful and if the particular response I have offered to the third question is viable. I hope this initiates a fresh conversation. Acknowledgments For thoughtful conversation and collaboration in relation to the 2013 Eastern APA symposium at which this paper was presented, the author would like to thank Joe Rouse, Melinda Fagan, and Alan Love. The paper’s central ideas have been developing for some time, and I am grateful to audiences at Boise State, Oberlin, U. Calgary, UC Davis, UC Irvine, U. Washington, SPSP 2011, and PSA 2014 for valuable feedback that is reflected especially in section 4 of this paper. References Andersen, H. (2010). Joint acceptance and scientific change: A case study. Episteme, 7, 248-265. http://dx.doi.org/10.3366/E1742360010000973. Bokulich, A. (2009). Explanatory fictions. In M. Suarez (Ed.), Fictions in science: Philosophical essays on modeling and idealization (pp. 91-109). New York: Routledge. Bokulich, A. (2011). How scientific models can explain. Synthese, 180, 33-45. http:// dx.doi.org/10.1007/s11229-009-9565-1. Cartwright, N. (1983). How the laws of physics lie. Oxford: Clarendon Press. Dear, P. (2006). The intelligibility of nature: How science makes sense of the world. Chicago: University of Chicago Press. De Regt, H. W. (2009). Understanding and explanation. In H. de Regt, S. Leonelli, & K. Eigner (Eds.), Scientific understanding: Philosophical perspectives (pp. 21-42). Pittsburgh: University of Pittsburgh Press. Elgin, C. (2004). True enough. Philosophical Issues, 14, 113-131. http://dx.doi.org/ 10.1111/j.1533-6077.2004.00023.x. Elgin, C. (2007). Understanding and the facts. Philosophical Studies, 132, 33-42. http://dx.doi.org/10.1007/s11098-006-9054-z. Elgin, C. (2009). Exemplification, idealization, and scientific understanding. In M. Suarez (Ed.), Fictions in science: Philosophical essays on modeling and idealization (pp. 77-90). New York: Routledge. Friedman, M. (1974). Explanation and scientific understanding. Journal of Philosophy, 71, 5-19. http://dx.doi.org/10.2307/2024924. Gilbert, M. (2000). Collective belief and scientific change. In Sociality and responsibility: New essays on plural subject theory (pp. 37-49). Lanham: Rowman and Littlefield Publishers. Goodwin, W. (2007). Scientific understanding after the ingold revolution in organic chemistry. Philosophy of Science, 74, 386-408. http://dx.doi.org/10.1086/522358. Hempel, C. G. (1965a). Aspects of scientific explanation. In Aspects of scientific explanation and other essays in the philosophy of science (pp. 331-496). New York: The Free Press.

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