Philosophy

Two major clarifications have greatly abetted the understanding and fruitful expansion of the theory of natural selection in recent years: the acknowledgment that interactors, not replicators, constitute the causal unit of selection; and the recognition that interactors are Darwinian individuals, and that such individuals exist with potency at several levels of organization (genes, organisms, demes, and species in particular), thus engendering a rich hierarchical theory of selection in contrast with Darwinâs own emphasis on the organismic level. But a piece of the argument has been missing, and individuals at levels distinct from organisms have been denied potency (although granted existence within the undeniable logic of the theory), because they do not achieve individuality with the same devices used by organisms and therefore seem weak by comparison. We show here that different features define Darwinian individuality across scales of size and time. In particular, species-individuals may develop few emergent features as direct adaptations. The interactor approach works with emergent fitnesses, not with emergent features; and species, as a consequence of their different mechanism for achieving individuality (reproductive exclusivity among subparts, that is, among organisms), express many effects from other levels. Organisms, by contrast, suppress upwardly cascading effects, because the organismic style of individuality (by functional integration of subparts) does not permit much competition or differential reproduction of parts from within. Species do not suppress the operation of lower levels; such effects therefore become available as exaptations conferring emergent fitnessâa primary source of the different strength that species achieve as effective Darwinian individuals in evolution.

Individuality and adaptation across levels of selection: How shall we name and generalize the unit of Darwinism? Stephen Jay Gould*† and Elisabeth A. Lloyd‡ *Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138; and ‡History and Philosophy of Science, Indiana University, 130 Goodbody Hall, Bloomington, IN 47405 Contributed by Stephen Jay Gould, June 2, 1999 Two major clarifications have greatly abetted the understanding and fruitful expansion of the theory of natural selection in recent years: the acknowledgment that interactors, not replicators, constitute the causal unit of selection; and the recognition that interactors are Darwinian individuals, and that such individuals exist with potency at several levels of organization (genes, organisms, demes, and species in particular), thus engendering a rich hierarchical theory of selection in contrast with Darwin's own emphasis on the organismic level. But a piece of the argument has been missing, and individuals at levels distinct from organisms have been denied potency (although granted existence within the undeniable logic of the theory), because they do not achieve individuality with the same devices used by organisms and therefore seem weak by comparison. We show here that different features define Darwinian individuality across scales of size and time. In particular, species-individuals may develop few emergent features as direct adaptations. The interactor approach works with emergent fitnesses, not with emergent features; and species, as a consequence of their different mechanism for achieving individuality (reproductive exclusivity among subparts, that is, among organisms), express many effects from other levels. Organisms, by contrast, suppress upwardly cascading effects, because the organismic style of individuality (by functional integration of subparts) does not permit much competition or differential reproduction of parts from within. Species do not suppress the operation of lower levels; such effects therefore become available as exaptations conferring emergent fitness-a primary source of the different strength that species achieve as effective Darwinian individuals in evolution. Darwinian Individuals and the Logic of Natural Selection Manifesting the resilience of our usual metaphors for stubborn persistence-from the classical Phoenix reborn from ashes to the vernacular alley cat with nine lives-the formerly anathematized concept (1, 2) of supraorganismal selection has emerged from previous calumny to a new status of intense discussion and growing importance (3). The logic of the theory of natural selection, as many evolutionary theorists and philosophers of science have recognized (4–12), assigns the status of causal agency in selection to interactors, defining them as individuals that: (i) Interact with the environment, broadly construed as all surrounding and influencing biotic and abiotic factors, in such a way that (ii) One or more of their traits imparts differential reproductive success through the interaction, so that (iii) Relatively more or less (compared with other individuals at their level) of their hereditary material (however packaged) passes to the next generation. We realize, of course, that several terms in this complex definition are rich in meaning and fraught with ambiguity, and that debate continues to surround many of the issues. But the basic framework and the recognition of a proper locus of causality have now achieved general approbation. Even though we accept this emerging consensus in favor of the interactor approach, we find that several problems still remain, none more pressing than learning how to think about the viscerally unfamiliar (and in many ways counterintuitive) supraorganismal levels of organization and selection. (Given the reductionist traditions of Western science, we are naturally more comfortable with suborganismal units of genes and cell lineages.) We claim that evolutionists have generally not appreciated the importance of higher levels, particularly the species level of selection, because species-individuals may not build many adaptations of their own. False emphasis on adaptation therefore leads biologists to downgrade the species level as only weakly operative in the processes of selection. We can understand how the undervaluing of species-level selection may have arisen by considering the recent literature. The sound conceptual basis for a hierarchical theory of selection has been winning respect and gaining ground during the past few years. The seminal works of D. S. Wilson and E. Sober (3, 13), based on the interactor approach, stand at the forefront of this important conceptual shift in evolutionary theory. As criteria for interactors at all levels, Sober and Wilson choose to emphasize-too restrictively, we shall argue-the properties of structural cohesion and functional design so central to our vernacular concept of conventional organisms and so vital to our practice of viewing the traits of organisms as adaptations.§ In defining their concept of an interactor, Sober and Wilson stress the ''level (or levels) at which natural selection actually operates, producing the functional organization implicit in the word 'organism' " (ref. 3, p. 591). They focus their attention on ''any biological entity whose parts have evolved to function in a harmonious and coordinated fashion'' (ref. 3, p. 606). But, in restricting their attention to functional integrity as a basis for adaptation, Wilson and Sober emphasize only one potential product of a process of evolution by natural selection. They claim that ''higher units of the biological hierarchy can be organisms, in exactly the †To whom reprint requests should be addressed. §In their important 1994 article (3), though not in their 1998 book (13), Wilson and Sober proposed some ill-considered definitions. Our criticism may seem small and merely terminological, but this unfortunate choice by Wilson and Sober will, if generally adopted, impose a severe restriction upon the range of reform opened up by replacing Darwin's single-level theory of selection on organisms (or the even more reductionistic "selfish gene" proposal) with a hierarchical theory of simultaneous selection at several legitimate levels of individuality. It would be a shame to impose such a limitation at the very dawn of a theory so richly imbued with potential for radical rethinking about the basis of evolutionary causality. In their 1994 article, Wilson and Sober restricted the term "individual" to the discrete "flesh and blood" body of vernacular understanding and extended the term "organism" to designate the general concept of a Darwinian interactor as a causal unit of selection at any level of the evolutionary hierarchy. They wrote: "We use the word 'individual' to refer to a single flesh-and-blood creature, such as a bird or butterfly. We use the term 'organism' to refer to any biological entity whose parts have evolved to function in a harmonious and coordinated fashion" (ref. 3, p. 606). We, on the other hand, following ordinary vernacular usage (developed, we think, for good reasons) strongly support the opposite usage of "individual" for the general Darwinian actor at any level of the hierarchy, and "organism" for the discrete body of single creatures in Darwin's conventional realm, usually, and properly, called "organismic selection." The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. 11904–11909 u PNAS u October 12, 1999 u vol. 96 u no. 21 same sense that [individual bodies] are organisms, to the extent that they are vehicles of selection'' (ref. 3, p. 605). This statement suggests that if higher units operate as vehicles of selection, then they must work like organisms in the harmony and coordination of their parts. But this claim cannot be supported, for the argument confuses one potential outcome or product of a causal process with the causal process itself. Higher-level selection processes do not necessarily require, nor do they invariably produce, functional organization or harmony of parts. In defending their definitions, Wilson and Sober claim that ''no one would be interested in group selection if it never resulted in group-level adaptation'' (ref. 3, p. 640). Some evolutionists do restrict their concerns in this manner; but many others do not consider group-level adaptations as a sine qua non for supraorganismic selection in evolution. Supporters of this broader scope of concern include Sewall Wright (14, 15), many evolutionists who maintain a Wrightian interest in population structure, and most architects of the theory of hierarchical selection (5, 16–23). More generally, the adaptationist approach establishes a mistaken and overly restrictive strategy for the analysis of speciesor clade-level selection, as Williams (24) has acknowledged. In this paper, we argue that the strategy of defining individuality by functional cohesion and adaptation of entities at all levels will stymie our understanding of the distinctive characteristics of Darwinian individuals at levels other than organismal. If we falsely restrict our concept of individuality to properties of cohesion, functionality, and adaptation, we miss the different styles of individuality-the scale-bound ''allometries,''¶ that make evolutionary interactors at levels above and below organisms such potent and distinctive units of evolution. As happens so often in Darwinian theory, an overemphasis on adaptation promotes our failure to grasp the richness of different styles of individuality by imposing on all levels the adaptive properties of the organism-the kind of individual that we know best, if only for the intuitions inspired by our personal residence in this particular, and in many ways rather peculiar, category! Agency and Causality in Natural Selection All concepts and categories in science are necessarily and inextricably theory-bound; raw nature dictates no unitary, inevitable scheme for parsing her continua. Taxonomies emerge only in the context of questions asked by investigators in their quest to understand how nature operates. Thus, the issue of what natural entities act as agents or units of selection depends crucially on the nature and logic of the theory of natural selection itself. The central and contentious issue of causal agency in natural selection-does Darwin's process work on organisms (as Darwin argued), on genes (as various reductionist accounts maintain), on supraorganismal units, or on some or all of these legitimate biological individuals simultaneously (as we and many others now hold)-has generated much confusion, arising not so much from dispute about empirical matters, but from conceptual problems about the nature, locus, and meaning of causality in Darwin's mechanism. In particular, many biologists have mistakenly equated the need for keeping a ledger of evolutionary changes through time with the task of identifying causal agents of change-a conflation of bookkeeping with causality. David Hull's important distinction between replicators and interactors (27) helped to clarify conceptual and empirical issues at the center of debates about units of selection. Hull modified Dawkins' concept of a replicator to designate any entity that can serve as a basis for copying itself. Hull's concept of interactor denotes an entity that interacts directly, as a cohesive whole, with its environment in such a way that replication becomes differential. For Hull, natural selection then becomes ''a process in which the differential extinction and proliferation of interactors cause the differential perpetuation of the replicators that produced them'' (ref. 27, p. 318; cf. ref. 11, pp. 317–318). More recently, Lloyd has analyzed the range of published positions on units of selection and evolution by distinguishing two additional entities of potential interest: the beneficiary and the manifestor-of-adaptation (refs. 28, 29; see other distinctions in refs. 11, l7, 30). Lloyd defines a beneficiary as an entity that benefits ultimately and in the long term from evolution by a selection process. A second and quite distinct version of the benefit question invokes the notion of adaptation. Evolution by a selection process may be said to benefit a particular entity under selection (at a particular level) by producing adaptations at that level (1, 2, 31, 32). In this approach, the entity actively selected (the interactor) benefits from evolution by selection at that level through its acquisition of adaptations. In this case, the entity then qualifies as a manifestorof-adaptation. As we have emphasized above, the key insight illuminated by these distinctions leads us to recognize that not all interactors are manifestors-of-adaptations, for benefit may also accrue passively at one level when an entity at that level expresses properties as structural side consequences of causes acting at other levels. These additional criteria of manifestor and beneficiary-ofadaptations have been advanced by other authors either explicitly or by passive conflation of these intuitively appealing ideas (given the favored status of adaptation as the focal concept of Darwinian tradition) with the two categories of Hull's classic division. Bookkeeping. Replication defines the key issue in our decisions about best ways to record evolutionary results. The gene represents the most appropriate unit for marking evolutionary change for two major reasons: one has always been recognized by selfish-gene theorists but misidentified as evolutionary causality; the other, rarely acknowledged or formulated, arises from a structural property of hierarchies. First, the gene operates as a maximally faithful replicator across generations, and bookkeepers can therefore record the evolutionary history of populations as changing relative frequencies of these stable items (as could not be done for sexual organisms, for example, because these entities disaggregate their personhood and pass only half their genotype to each offspring). Second, genes become preferred units of bookkeeping because they represent the lowest-level individuals subject to clear and accurate recording in a genealogical hierarchy of inclusion (genes within organisms within demes within species, etc.). As a formal and general property of their structure, hierarchies of this kind manifest an important asymmetry (33), in that differential sorting at higher levels also sorts each lower level as a necessary consequence. (If, for example, some species become extinct within a clade, the relative frequencies of all lower-level individuals must change, because the extinction of a species must also remove certain kinds of organisms, certain kinds of genes, etc.). Differential sorting at lower levels, however, need not affect the frequencies of higher-level individuals at all. (The copy number of a gene may increase by gene selection within some organisms of a species without affecting the selective prowess of these organisms, or that of the deme or species containing them.) Thus, because genes are the only biological individ- ¶Inthispaper,weobviouslyusetheterm"allometry"somewhatmetaphorically.Allometry (25, 26) classically refers to differences in organismic properties (whether of form, physiology, or behavior, and whether expressed in ontogeny, phylogeny, or structural series of taxonomic relatives) that are systematically correlated (whether causally or merely descriptively and whatever the quantifiable nature of the relationship) with changes in size. In other words, allometry represents the locus classicus for studying the effects of scaling on organisms. But scaling in both size and time also defines the fundamental relationships of units in nature's structural hierarchy of inclusion: genes within cell-lineages within organisms within demes within species within clades. This paper explores the question of whether the different properties that establish Darwinian individuality among the various units of nature's hierarchy (particularly for genes, organisms, and species) arise as consequences of the fundamental scaling in size and time that pervades and defines this hierarchy. The designation of such potential differences among units as "allometric" therefore strikes us as an appropriate and potentially interesting extension of this basic biological concept. Gould and Lloyd PNAS u October 12, 1999 u vol. 96 u no. 21 u 11905 EV O LU TI O N uals reliably sorted by any process of selection acting at any level, the books of evolution are best kept at the genic level. This important conclusion about the evolutionary status of genes does not imply that genes also act as causal units or agents of natural selection. Defining Darwinian Individuals. The proper definition of a Darwinian individual constitutes one of the most challenging and fascinating issues in the formulation of causality under natural selection. Three sets of criteria, ranging from conventions of ordinary language to specific requirements of Darwinian logic, define Darwinian individuality in terms of greatest generality and abstraction. First, a biological individual must manifest the essential traits required to define such distinctive discreteness in ordinary language and not specifically as a scientific or evolutionary concept. The three properties of distinct birthpoint, distinct deathpoint, and sufficient stability in between will mark a biological individual as a potential Darwinian interactor by defining the difference between a discrete entity and an arbitrary segment of a smooth temporal continuum. Second, these vernacular individuals must then manifest the two essential properties that permit them to function as evolutionary agents in genealogical systems evolving by Darwinian principles: (i) they must generate offspring (in potentially differential numbers among individuals), and (ii) these offspring must be more like them (carry more of their hereditary contributions) than like other members of the parental generation. Without such continuity in heredity, differential reproductive success will impart no Darwinian advantage to parental individuals). Third, these evolutionary individuals must function as interactors with the environment, as defined above, so that they may be treated as Darwinian individuals, or causal agents in the process of natural selection. We might label these three sets as criteria of vernacular, evolutionary, and Darwinian individuality. Individuals at several levels of an ascending structural and genealogical hierarchy manifest all these criteria nearly all the time, or at least often enough to act as important Darwinian individuals: (i) genes, if they can differentially replicate within organisms; (ii) cell lineages when not suppressed in replication by functional demands of surrounding organisms (34); (iii) organisms virtually all the time (leading to their nearly exclusive status in Darwin's own formulation); (iv) demes under conditions achieved often enough in nature (16, 17), however firmly most evolutionary biologists rejected such an idea during the 1960s and 1970s (1, 2); and (v) species nearly all the time (especially when punctuated equilibrium holds and we can reject Fisher's powerful but controvertible arguments (35) for the true existence, but necessary impotence, of selection at this level). With this account of Darwinian individuals in hand, we can address the basic challenge: how do different-sized biological objects manifest these properties? The Allometry of Individuality Biologists have long recognized the power of allometry, or alterations in form causally correlated with changes to size, to explain systematic and predictable scale dependencies in the anatomy and physiology of organisms (25, 26, 36). The differential scaling of surfaces and volumes, first codified by Galileo in 1638, defines the locus classicus of this subject. Haldane (ref. 37, p. 21) wrote in his most famous essay: ''Comparative anatomy is largely the story of the struggle to increase surface in proportion to volume.'' We might generalize the concept of allometry or scale dependency and ask whether individuality might manifest sensible changes in style across the great range of size represented by the three most widely discussed levels of an even more extensive array: the gene-individual, the organism-individual, and the speciesindividual. If allometric effects can be so extensive, so profound, and so orderly within the smaller range of sizes and greater coherence of substrates represented by organisms from microscopic unicell to blue whale or sequoia tree (thus inspiring Haldane's famous remark), we might anticipate an even greater spate of interesting and systematic differences across the larger range of sizes in the hierarchy of Darwinian interactors. In defining three principal levels of individuality-genes, organisms, and species-little debate has arisen about the last two criteria for identification: the evolutionary and Darwinian properties of individuality discussed above. That is, individuals of all three levels bear offspring more like themselves than like others in the population, and all can clearly operate as interactors in a process of selection. However, all levels of individuality do not fulfill in the same manner the three major vernacular criteria of discrete birthpoint, deathpoint, and sufficient stability. Bounding and Functioning. Organisms meet these vernacular criteria with the two essential features that define our usual concept of the organic: (i) organisms are coherently bounded in space and kept recognizable in form by a physical skin that separates the self from the outside world, a distinction often buttressed by various devices-an immune system as the most prominent example-that can recognize and disarm or eliminate transgressors into the interior space; and (ii) organisms are functionally defined by interdependence and interaction among parts, such that separate units or organs (liver, heart, brain, etc.) maintain little vital meaning or potential existence in isolation and work only as adaptive components of the entirety. Needless to say, as with all definitions in the maximally various realm of natural history, even these criteria do not hold in every case; celebrated ambiguities occasionally arise, especially for colonies [the coelenterate siphonophores have served as the classic example through two centuries of debate (38, 39), for these creatures are apparently composed of genealogical organisms so specialized for different roles within the colony that they cannot exist independently and therefore function more like organs than full persons.] But genes and species do not clearly manifest these essential features of bounding and functionality, although both levels evidently meet the defining criteria of discrete birthpoint, deathpoint, and sufficient stability. The apparent failure of species to be sufficiently ''organismic'' in spatially coherent packaging and functional interaction among subparts may be responsible for the common impression that, if species can be construed as Darwinian individuals at all, they cannot match conventional organisms in potential power as agents of selection. We wish to argue in this paper that entities at other levels of organization-species in particular-can operate as effectively as organisms in the role of Darwinian individual. Biologists have generally failed to appreciate this equal potential, because allometric effects at levels above and below organisms impart the requisite criteria of coherent birthpoint, deathpoint, and sufficient stability through features different from those developed by organisms. At a level below organisms, genes achieve a form of boundedness by beginning and ending signals along the linear array of a DNA molecule, and they manifest some degree of functional organization through various devices, including repair mechanisms, for some kinds of alterations. Genes, however, do not manifest with any force even remotely approaching the capacities of organisms the functional integration that grants ''sufficient stability'' to organisms by regulating the sizes and interactions of subparts. Nonetheless, most genes match or exceed most organisms in stability over a full lifetime, by the different, allometrically engendered strategy of very slow cycle time for mutational change vs. intervals between replications that pass gene-offspring from one generation to the next. Thus, in the overwhelming majority of cases, genes retain sufficient stability through their lives as interactors, and therefore fulfill all vernacular criteria of individuality. 11906 u www.pnas.org Gould and Lloyd Species Individuality. The features that grant vernacular individuality to species depart even further, as a consequence of upward scaling in size and time, from attributes that play the same role in organisms. But ''different'' need not imply ''worse'' for setting the strength of individuality needed by Darwinian interactors to operate in processes of selection. (Here we confine our attention, as do most authors, to sexual species. The problem of defining asexual species and the debate over whether such a concept holds meaning lies outside the scope of this paper, but retains great fascination and high status as one of the most important unresolved issues in evolutionary theory.) The species-individual manifests important properties of both boundedness and integration among subparts, but by mechanisms strikingly different from those used by organisms; the difference arises from the allometric effects of upward scaling. At the species level, the agent of bounding cannot be a physical skin, so the ''shape'' (or geographic range) of a species-individual presents neither a fixed form nor a predictable ontogeny; in fact, the species-individual need not even be spatially continuous, i.e., subsections may inhabit disjointed areas. Moreover, although species match organisms in the strength of integration among subparts, species do not achieve such integration by specialization and mutual interdependence of these subparts in the service of the whole. Rather, species attain both properties of bounding and integration among subparts by their defining feature of reproductive isolation, which acts as the rough analog of an immune system at the organismic level. Each component of the species-individual (that is, the constituent organism-individuals) breeds successfully only with other components of the same species and also excludes similar components of different species by an inability or disinclination to mate (a defining criterion of sexual species from Buffon's day to ours). Components of other species need not be excluded from the body space (geographic range) of the species in question. By analogy, most organism-individuals, whatever their immune defenses, tolerate myriads of commensals and parasites within their own bodies. This reproductive style of policing works effectively in maintaining the integrity of species. (Incidentally, for this primary reason, species selection can be more easily defended than interdemic selection, where invasion from parts of other demeindividuals often threatens the integrity of the deme in question.) The Scaling and Limits of Adaptation in Characterizing Darwinian Individuals Adaptation must be recognized as a potential outcome of a process of selection, not as the definition of the mechanism of selection itself. In anglophonic historical traditioni and by the logic of Darwinian functionalism,** adaptation has been favored as the preeminent subject of evolutionary analysis; this focus has recently (43) and in the past (41, 42) been vigorously challenged for different reasons. Given the persistence of this loyal opposition and the important theoretical separation of mechanism and effect (in this case, the status of adaptation as one class of effects, however traditionally favored among potential alternatives), we must question the common use of achieved adaptation as a primary criterion for the strength of a selective process. The interactor criterion for defining natural selection as a causal process requires that a trait of a Darwinian individual impart a level-specific component of fitness to that individual through a correlation of the trait with the selective internal and external environment. Nothing in the logic of this definition requires that the trait providing such fitness be an adaptation of the Darwinian individual at the level of its immediate interaction. The trait need only impart a unique component of fitness; it does not have to rank as an emergent character of the Darwinian individual under consideration.†† Species selection becomes especially interesting in evolutionary theory as a locus of interacting effects from several levels of organization, whereas the traditional organismic level works more by suppression and exclusivity, that is, by using its considerable power to build adaptations at its own level and by excluding effects from other levels. Almost by definition (of behavior in random systems), such effects must be deleterious to the precisely maintained functional integrity of the organism; for any trait built at another level must be viewed as effectively random with respect to its operation at a new focal level. For example, in the case that inspired our previous paper (45), and that may rank as most important in evolution by virtue of generality, the variability of traits within species often imparts an emergent component of fitness to the species as a Darwinian individual. But variability represents an ensemble or aggregate trait; variability therefore cannot be regarded as an emergent character of the species. (Emergent traits at any level must arise by interaction among constituent parts-in the case of species-individuals, among organisms.) As an aggregate character, variability need not be construed as an adaptation at the species level. The common, and often unconscious, bias of defining the salience of an evolutionary process by its role in the production, maintenance, or utilization of adaptations has stymied our understanding of selection at supraorganismic levels, where adaptation may not hold the definitive status generally granted to this result in the organismic realm. This error has been catholic in distribution; for both supporters and denigrators of supraorganismic selection and of the interactor approach have mistakenly linked the defense of their contrary positions to the presence and production of adaptations. Hull, for example, coined the term ''interactor'' for the active causal agent in evolution by selection, but he nevertheless held that the validation of supraorganismic selection depends on ''whether entities more inclusive than organisms exhibit adaptations'' (ref. 27, p. 325). Several of the strongest supporters of species selection, including an author of this paper in previous work (33), have linked their defense to the identification of emergent characters arising as adaptations at the species level; whereas they should have used the broader, more justifiable, and more fully operational emergent fitness approach. iThe space and nature of this forum do not permit adequate commentary on this fascinating historical issue, but Darwin's decision to emphasize adaptation as the cardinal phenomenon facing any proper theory of life must be judged as neither idiosyncratic nor logically entailed, but rather as a sensible consequence of Darwin's fealty to a distinctively English tradition in natural history dating back to foundational works by Boyle and Ray in the late 17th century, and culminating in Paley's Natural Theology of 1802. The Argument From Design-the claim that God's existence and attributes lie revealed in the exquisite design of organisms and the harmony of ecosystems-formed the centerpiece of this particular tradition, in clear distinction from most continental preferences for locating God's hand in the taxonomic order (the "laws of form") pervading the interrelationships of organisms. British natural theologians used the vernacular word "adaptation" to describe this exquisite design that presumably flowed from God's creative grace. The essence of Darwin's philosophical radicalism lies in his decision to retain the core problem (the explanation of good design, or adaptation) while utterly inverting the Paleyan explanation by substituting organisms struggling for their individual advantage for God's overarching and benevolent intent. **Most famously expressed by Darwin himself in a familiar passage from the Introduction to the Origin of Species (ref. 40, p. 3): "It is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had descended, like varieties, from otherspecies.Nevertheless, suchaconclusion,evenifwell founded,wouldbeunsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which most justly excites our admiration." ††The emergent fitness vs. emergent character criterion has sparked an interesting debate (5, 21). One of us (S.J.G.) formerly preferred the latter alternative (33) before being persuaded by the other (E.A.L.) of the greater validity of the fitness criterion for theoretical reasons rooted in the logic of selection as a causal process and for practical reasons (the imperfection of historical records-see below). Grantham (44) provides a good account of this debate and of our suggested resolution. Gould and Lloyd PNAS u October 12, 1999 u vol. 96 u no. 21 u 11907 EV O LU TI O N Detractors of both supraorganismal selection and the interactor approach have often, in a strange irony, grasped and explicated the concept of interaction with skill and understanding, but have then rejected the interactor approach to defining evolutionary causality because they correctly recognized its disconnection with the concept of adaptation. But they erred in using adaptation as the necessary and sufficient criterion for inferring evolutionary causality. Williams (24), for example, provides the finest description of the interactor approach ever written, but then wrongly locates causality in an alternate ''codical'' realm of replicating information rather than in the material domain of Darwinian individuals (see analysis in ref. 35). As one author (E.A.L.) of the present paper argued (29), Dawkins (46) also rejects the interactor (''vehicle'' in his terminology) approach, and, although he explicates the concept with force and accuracy, he confuses questions about ''beneficiaries'' and ''manifestors-of-adaptations'' with the identification of interactors as causal agents in selection. Lloyd (29) writes of Dawkins: ''He begins by admitting that groups can function as interactors. His argument that groups should not be considered real units of selection amounts to the claim that the groups are not the ultimate beneficiaries.'' In misidentifying replicators as primary causal units, Dawkins appeals to their role as beneficiaries of adaptations and denies interactors their appropriate causal status: ''It is still genes that are regarded as replicators which actually survive (or fail to survive) as a consequence of the (vehicle) selection process'' (ref. 46, p. 100). Dawkins' inability to grasp the causal role of interactors in selection processes arises from his limited focus on a particular problem that motivates his personal interest: namely, what is ''the nature of the entity for whose benefit adaptations may be said to exist'' (ref. 46, p. 81; our emphasis). Unfortunately, Dawkins interprets all claims for supraorganismal selection as requiring statements about beneficiaries and manifestors of adaptations as well as about interactors; and this overextended definition leads to a serious misreading of authors who pursue the interactor question alone, as we do here. Adaptations: Organisms vs. Species. By virtue of their defining properties of boundedness in form and interactivity of parts, organisms-the Darwinian individuals that we must know best for the most ineluctably personal of reasons-become functional units replete with adaptations as a consequence of Darwinian processes. But suppose-as we believe to be the case-that this proneness to develop adaptations represents an allometrically based property of organismic individuality that does not translate with similar intensity to the construction of individuality at other levels, where disparate ranges of size and time enjoin different properties to meet the defining criteria. In particular, species-individuals may develop relatively few species-level adaptations, not as a mark of weakness for species as Darwinian interactors, but as an allometric property of individuality at this level. Perhaps the most interesting difference between the organism and the species as evolutionary and Darwinian interactors lies in the difficulty of building adaptations when reproductive exclusivity among subparts (rather than boundedness of overall form and functional interaction among constituent parts) defines individuality, thereby allowing species-individuals to interact with the environment through traits that are not species-level adaptations. The emergent fitness approach works especially well in identifying traits that may not exist as adaptative characters of the species, but may impart fitness by upward causation from lower levels (5). Such traits, originating for causal reasons at other levels, achieve expression as ''side consequences'' at the species level, where they may then become important, even vital, exaptations (47)‡‡ by imparting useful effects (emergent fitness in this case) to the species-individual. We do not, of course, hold that species develop no genuine species-level adaptations as truly emergent traits. But we do emphasize two features that make the identification of emergent traits a poor primary criterion for identifying species selection: (i) Emergent characters are difficult to define because their elucidation usually requires considerable historical knowledge of details in the ancestral history of particular lineages to distinguish truly emergent traits from cascading effects of properties built at other levels. Such density of historical information can rarely be obtained from imperfect fossil records. (ii) Emergent characters represent only a (perhaps lowfrequency) subset of traits that can serve species-individuals by imparting emergent species-level fitness in a causal process of interaction with the environment. The paucity of well-documented cases has been proposed with apparent force, after many years of discussion, as a telling argument against the general efficacy or even the existence of species selection. But current failure may represent an artifact of using the overly restrictive and often nonoperational criterion of emergent characters, inspired by misplaced emphasis on adaptation. Only emergent traits can rank as adaptations at the species level; we will unnecessarily restrict our explanatory compass if we use the generation of adaptations, rather than the proper criterion of fitness in interaction, to define causal agency in natural selection. If we move to the far less restrictive and theoretically preferable criterion of emergent fitness-a fully operational proposition requiring no historical knowledge of the level of origin or adaptive status of a trait-then we may reconceive species selection as not only fully testable, but also potent and potentially ubiquitous. Conclusions The most salutary effect of this rethinking lies in its potential for breaking a conceptual logjam that has effectively precluded fruitful research on this subject. Once we understand that to function well as Darwinian interactors, species-individuals either may or may not develop design-type adaptations, then we may clearly distinguish two vital questions for research. The previous conflation of these questions has long stymied progress in this important domain of evolutionary theory. (i) Do species function as Darwinian individuals and interactors with an active and significant role in evolution by selection? (ii) Does the evolution of species-level interactors produce species-level engineering adaptations, and if so, how often? For most of the history of the species selection debate, these two questions have been treated as identical. In other words, asking whether species could be construed as units of selection meant asking whether species operated both as interactors and as manifestor-of-adaptations. The desired breakthrough may result from the proper separation of these two questions, and from the different answers given to each: a resounding ''yes'' to the first, and a ''not very often, given the allometric properties that define individuality at the species level'' to the second. With this principled separation, we may finally identify the distinctive and primary power of the species-individual as a Darwinian interactor, a strength that arises from scale-bound allometric features and precludes an important role for direct ‡‡Gould and Vrba (47) defined exaptations as features evolved for one reason (whether or not as adaptations), and then coopted for utility in another role; the bird feather, evolved for thermoregulation and later coopted for flight, for example. Such coopted structures cannot properly be called adaptations for current usage, because they did not evolve to work in their present manner. Yet such structures may be as useful to the organism, as essential to survival and as biomechanically fit (however fortuitously so) to a new usage as any feature explicitly evolved for its current function. Thus, Gould and Vrba suggested that this previously unnamedcategoryofstructureswithcooptedutilitybecalled"exaptations," that is, takenfrom a former (ex) state, for utility (apt) in a new role, rather than adaptations, designed for (ad) their current utility (apt). The concept of exaptation implies an obvious and principled extension to the passage of effects across levels of organization: If a feature evolved at one level produces automatic and consequential effects on Darwinian individuals at a higher or lower level, these effects, if then used at the new level, must be called exaptations. Their source and origin lie at another level, and their original function, if any, must be different from their current function in the focal individual now benefiting from the emergent fitness they provide. 11908 u www.pnas.org Gould and Lloyd adaptation by emergent traits at the species level. The organism, in securing individuality by boundedness and functional integration of subparts, has evolved powerful mechanisms to suppress selection at lower levels within itself, lest internal proliferation of some subparts at the expense of others discombobulate the functional operation of the whole and eventually kill the organism. As Buss (34) shows in his important book, organisms thus effectively cut off selective proliferation at the next lower level of the cell-lineage. (When they fail to do so, we call the outcome cancer.) At the still lower gene level, selection within organisms can be more effective, because up to a certain point, proliferation of multiple copies of genes within the genome may not affect the organismal phenotype, thereby escaping ''notice'' by the evolved policing systems of organismic integrity. The sexual species does not so rigidly suppress the selection of subparts within itself, having neither the need nor the opportunity to do so. The sexual species, maintaining individuality primarily by the reproductive exclusivity of subparts (organisms), cannot be strongly threatened by differential proliferation of these subparts. Some features of populations, gene flow for example, could be interpreted as mechanisms of suppression by spreading and dilution, but such features can also transform the species-individual from within. All mechanisms of transformation from within, including ordinary anagenetic change by conventional organismic selection, act as higher-level analogs of Lamarckism, and provide a distinctive source of evolutionary potency for species-individuals, rendered all the more curious and interesting as an allometric effect because the organismic level, as a defining feature, actively precludes any comparable mechanism for adaptive transformation from within during a single lifetime. In any case, the species maintains no evolutionary interest in such general and effective suppression, for differential proliferation of subparts often works to the selective advantage of species, either by adaptive anagenetic transformation or by production of new and different daughter species. The analogous situation at the lower level usually spells disaster for organisms, thus establishing one of the most interesting and important allometric differences between levels of evolutionary organization. The species-individual, by not suppressing selection at lower levels within itself, thereby maintains a large reservoir of nonemergent, sum-of-the-parts traits that are built at these lower levels but provide potential exaptive benefit to the species. These traits cannot be viewed as actively evolved adaptations at the species level; but they can (and probably do) provide a major component of emergent fitness, crucial to the success of species-individuals in the process of species selection. One might argue that such nonsuppression of lower levels defines and establishes the most distinctive power of the species as a Darwinian individual. For the species-individual then meets the external world with an extensive suite of both actual and latent fitness providers, built at several levels, but all working to its advantage-including some genuine species-level adaptations assembled from emergent traits and a larger set of potential crosslevel exaptations provided by upward causation from traits actively evolving at lower levels and thereby able to impart emergent fitness to the species-individual. We therefore venture the following ironic conclusion about distinctive allometric features of the species as a source of strength in selection. The species-individual, as a Darwinian interactor in selection at its own level, operates largely with cross-level exaptations arising from unsuppressed evolution of subparts (primarily organisms) at lower levels within itself. Such nonsuppression acts as a source of power by permitting species to draw upon a wider pool of features than organisms can access (for the organismic style of individuality enjoins active suppression of most selection at lower levels within itself). By not suppressing this evolutionary churning from within, the species-individual gains enormous flexibility in remaining open to help from below, expressed as exaptive effects that confer emergent fitness. Rather than viewing this nonsuppression of aid from other levels, with the accompanying failure to build many active adaptations at its own level, as a sign of wimpy weakness for the species-construed as a ''poor organism'' in the implication of most traditional thought-we should rather interpret these allometrically driven properties as cardinal strengths, and recognize the species as a ''rich-but-different'' Darwinian individual. The species, in this view, acts as a shelter or arbor that holds itself fast by active utilization of the properties that build its well-defined individuality. By not suppressing internal change and thereby gaining a large supply of upward cascading exaptive effects, species use the features of all contained lower-level individuals through the manifestation of their effects on the shelter itself. The species, through its own distinctive features of individuality, and requiring neither indulgence nor apologia from human understanding, will continue to operate as a powerful agent in Darwin's world whether or not we parochial organisms, limited by our visceral feelings and traditions of language, choose to expand our view and recognize the sources of evolutionary potency at distant scales of nature's hierarchy. 1. Williams, G. C. (1966) Adaptation and Natural Selection (Princeton Univ. Press, Princeton, NJ). 2. Maynard Smith, J. (1976) Q. Rev. Biol. 51, 277–283. 3. Wilson, D. S. & Sober, E. (1994) Behav. Brain Sci. 17, 585–654. 4. Griesemer, J. R. & Wade, M. (1988) Biol. Philos. 3, 67–96. 5. Damuth, J. & Heisler, I. L. (1988) Biol. Philos. 3, 407–430. 6. Lloyd, E. A. (1988) The Structure and Confirmation of Evolutionary Theory (Greenwood, Westport, CT). 7. Sober, E. (1984) The Nature of Selection: Evolutionary Theory in Philosophical Focus (MIT Press, Cambridge, MA). 8. Sober, E. & Lewontin, R. C. (1982) Philos. Sci. 47, 157–180. 9. Wimsatt, W. (1980) in Scientific Discovery: Case Studies, ed. Nickles, T. (Reidel, Dordrecht, the Netherlands). 10. Wimsatt, W. (1981) Proc. Philos. Sci. Assoc. 1, 122–183. 11. Brandon, R. N. (1982) Proc. Philos. Sci. Assoc. 2, 315–323. 12. Brandon, R. N. (l990) Adaptation and Environment (Princeton Univ. Press, Princeton, NJ). 13. Sober E. & Wilson, D. S. (1998) Unto Others: The Evolution and Psychology of Unselfish Behavior (Harvard Univ. Press, Cambridge, MA). 14. Wright, S. (1931) Genetics 16, 97–159. 15. Wright, S. (1980) Evolution 34, 825–843. 16. Wade, M. J. (1978) Q. Rev. Biol. 53, 101–114. 17. Wade, M. J. (1985) Am. Nat. 125, 61–73. 18. Goodnight, C. J. (1990) Evolution 44, 1614–1624. 19. Goodnight, C. J. (1990) Evolution 44, 1625–1636. 20. Goodnight, C. J., Schwartz, N. M. & Stevens, L. (1992) Am. Nat. 140, 743–761. 21. Arnold, A. J. & Fristrup, K. (1982) Paleobiology 8, 113–129. 22. Uyenoyama, M. K. & Feldman, M. W. (1980) Theor. Popul. Biol. 15, 58–85. 23. Uyenoyama, M. K. & Feldman, M. W. (1980) Theor. Popul. Biol. 17, 340–414. 24. Williams, G. C. (1992) Natural Selection: Domains, Levels and Challenges (Princeton Univ. Press, Princeton, NJ). 25. Huxley, J. S. (1932) Problems of Relative Growth (MacVeigh, London). 26. Gould, S. J. (1966) Biol. Rev. 41, 587–640. 27. Hull, D. L. (1980) Ann. Rev. Ecol. Syst. 11, 311–332. 28. Lloyd, E. A. (1992) in Keywords in Evolutionary Biology, eds. Keller, E. F. & Lloyd, E. A. (Harvard Univ. Press, Cambridge, MA). 29. Lloyd, E. A. (1999) in Thinking About Evolution: Historical, Philosophical and Political Perspectives, eds. Singh, R., Krimbas, C., Paul, D. & Beatty, J. (Cambridge Univ. Press, New York). 30. Mitchell, S. D. (1987) Philos. Sci. 54, 351–367. 31. Eldredge, N. (1985) Unfinished Synthesis: Biological Hierarchies and Modern Evolutionary Thought (Oxford Univ. Press, New York). 32. Vrba, E. (1984) Syst. Zool. 33, 318–328. 33. Vrba, E. & Gould, S. J. (1986) Paleobiology 12, 217–228. 34. Buss, L. (1987) The Evolution of Individuality (Princeton Univ. Press, Princeton, NJ). 35. Gould, S. J. (1994) Proc. Natl. Acad. Sci. USA 91, 6764–6771. 36. D'Arcy Thompson, W. (1917) On Growth and Form (Macmillan, London). 37. Haldane, J. B. S. (1927) Possible Worlds (Chatto & Windus, London). 38. Huxley, T. H. (1858) The Oceanic Hydrozoa (The Ray Society, London). 39. Haeckel, E. (1888) Report on the Siphonophorae (Zoology of the Challenger Expedition, Part 77, London). 40. Darwin, C. (1859) The Origin of Species (Murray, London). 41. Galton, F. (1889) Natural Inheritance (Macmillan, London). 42. Bateson, W. (1894) Materials for the Study of Variation (Macmillan, London). 43. Gould, S. J. & Lewontin, R. C. (1979) Proc. R. Soc. Lond. B 205, 581–598. 44. Grantham, T. A. (1995) Annu. Rev. Ecol. Syst. 26, 301–321. 45. Lloyd, E. A. & Gould, S. J. (1993) Proc. Natl. Acad. Sci. USA 90, 595–599. 46. Dawkins, R. (1982) The Extended Phenotype: The Gene as the Unit of Selection (Oxford Univ. Press, Oxford). 47. Gould, S. J. & Vrba, E. S. (1982) Paleobiology 8, 4–15. Gould and Lloyd PNAS u October 12, 1999 u vol. 96 u no. 21 u 11909 EV O LU TI O N


Philosophy

Empathic Design for Community Resilience Subjects: Engineering, Civil Contributors: Saleh Afroogh , Amir Esmalian  Submitted by: Saleh Afroogh Definition 1. Empathy: Definition and Characteristics Empathy in psychology was considered as a research topic of experimental research in the early 20th century, and since then, it has been explored in several major fields of cognitive, developmental, social, and clinical psychology . The new research on empathy as a major part of emotional intelligence in the late 20th century, however, made it a central concept in some significant psychological and psychotherapist research studies. Recently an increasing number of studies have been conducted on the role of empathy in engineering education and practice . In a general sense, empathy means the ability to understand other people's thoughts and feelings as well as the capacity of emotive treatment with them. It is emphasized in the literature that awareness is a necessary component of empathy, which distinguishes the concept of empathy from emotional contagion. "With empathy, the observer is aware that this feeling is a result of perceiving emotion in the other. With emotional contagion, the emotion is captured, but the observer lacks this awareness, and the observer believes this feeling to be his/her own" . That is, psychological empathy is a result of a self-reflexive reflection and is not just an incident (Notice that there is a semantical similarity between empathy and some other concepts like sympathy and compassion; however, they are not the same. Sympathy has a more emotive meaning and refers to "a vicarious emotional reaction based on the apprehension of another's emotional state or situation, which involves feelings of sorrow or concern for the other" whereas compassion means "the feeling that arises in witnessing another's suffering, and that motivates a subsequent desire to help" ). According to its origins and functions, empathy can be categorized into the following three kinds: cognitive empathy, affective empathy, and conative empathy. Cognitive empathy refers to the study of the ability and accuracy of the understanding of other people's thoughts in different contexts. Empathy, in this sense, is an epistemic tool to help us understand and know what others' minds are . Some psychologists emphasize the congruency of the observer's empathic mental state with the mental state of the individuals who are the object of the empathic treatment, while some others deny the possibility of the complete congruency . However, it is intuitive and largely plausible that cognitive empathy is not only available in some deep levels, but also, it is an indispensable part of our everyday life when we are talking or thinking about other people's thoughts, beliefs, and actions. Affective empathy refers to the study of emotional responses of human beings to the encounter of others' conditions. Affective empathy is usually formed after the apprehension of other people's feelings Empathic design, which is the outcome of embedding the empathic approach in community resilience, will meet all four critical features of any models which are supposed to satisfy both physical resilience and humanistic considerations. It holds that in addition to the technical knowledge, engineers have to care about the humanistic side of the engineering process as well. Empathic design refers to a design in which the designers, as well as the technical specifications, consider the humanistic aspects of the system in virtue of three types of empathy, namely, cognitive, affective, and conative. The empathic design brings about an inclusive and effective community resilience approach that is human-centric, individual and communal sensitive, justice-oriented, and value-based consistent. [1] [2][3][4][5] [6][7][8][9][10] [1] [11] [12] [1][13][14][15] and problems and sometimes entails some responsive actions. It can be thought of as the middle step, which is proceeded by cognitive empathy and would sometimes be followed by conative empathy, which is a professional and pragmatic tool in caring for other people . Affective empathy is semantically close to sympathy. Conative empathy refers to the study of the practical application of taking supportive actions in response to other people's feelings and problems. This kind of empathy is a professional and pragmatic concept, which refers to an empathic treatment with the people (like e.g., clients, stakeholders, or patients) in practice . Conative empathy is the most apparent kind of empathy which would be fully objective and observable. It is also a necessary part of some clinical professions like psychologists and psychotherapists who apply it in assisting their patients. Conative empathy is logically preceded by affective and cognitive empathy. Accordingly, a comprehensive definition of empathy is an affective one which is originated from cognitive empathy and leads to a conative one. 2. Empathic Design for Community Resilience Empathic design leads to an inclusive and effective approach to resilience design which requires to be human-centric, individual and communal sensitive, justice-oriented, and value-based consistent. These major expectable characteristics of an inclusive model for community resilience enable turning from the pragmatic approach in engineering design to a more fundamentally epistemic one. 2.1 Being Human-Centric An effective resilience design would be human-centric in two senses, which both require cognitive empathy. First, community resilience has been recently defined in terms of recovering capability of stakeholders, which are affected by disaster and natural hazards . In fact, the concept refers to returning the capability of those affected humans to their initial capability in the pre-disaster situation. Capability itself is modal philosophical concepts, and more specifically, human capability is a psychological term as such. Therefore, a central part of resilience design would be related to the human side, which is in direct relation with the physical and infrastructural aspects. Secondly, as discussed above, engineering aims at well-being and reducing human beings' suffering. It follows by necessity to consider human beings' real needs and problems, and design in a way that resolves those. Thus, a resilient engineering system should also aim at reducing human suffering, and this goal would be obtainable only if the humanistic sides of systems become "understood" by engineers. This "understanding of the humanistic side" cannot be attained by implementing empirical approaches. This understanding is not limited to the physiological needs of the individuals; it is rather more relevant to subjective psychological and anthropological needs, other minds' feelings and experiences. Empathy as a "non-inferential and non-theoretical method of grasping the content of other minds became closely associated with the concept of understanding" . Put in other words, cognitive empathy, as opposed to other empirical tools like experiments, has unique features that make a bridge between human subjective feelings, inferences, and interpretations about the outward world. So, a human-centric approach for designing resilient systems requires subjective epistemic tools like cognitive empathy. 2.2 Being Both Individual-Sensitive and Communal-Sensitive Community resilience requires the recovery of the system's performance. It is broadly supposed that the engineering system resilience has to be considered at the community level. Recent studies have suggested that community resilience should consider the specific needs of individuals because the performance of a community is the function of its individuals . However, community resilience is not simply a one-to-one function of its individuals' resilience; rather, there is another concept as communal resilience as well. Thus, the relation between the community and individuals should be explored to realize the resilience feature of a system. The collection and interaction among the individuals sometimes cause [1][16][17][18] [1][19][20][21][22] [23] [12] [23] the emergence of some patterns at the community level, which cannot be seen just by looking at the individual level. Thus, an inclusive and efficient approach for designing resilient systems requires considering both individual and communal resilience, which both need different levels and kinds of empathy. From a sociological point of view, there are two major theories on the semantic of the community proposed by Weber and Durkheim. Weber focuses more on individual autonomy in constructing the features of a society. Weberians believe that a community is a function of its individuals . Durkheimians, on the contrary, propose that the features of a society are not equal to the one-to-one features of its individuals. A society is more than a simple aggregation of its individuals. He points out "social facts" as the distinguishing features of a society which are not reducible to individual-level facts . For example, in a soccer team, the team's performance is not equal to the collection of each player's performance individually. The interaction among the team members plays a critical role in the final performance of the team in addition to their individual functions. Paying attention to the major opposite differences between the two points of view of an individual and a communal level leads us to two important points on the concept of resilience. First, we cannot simply ignore the individual level in community resilience. There is a meaningful interaction between these two levels, and every impact on individual resilience affects the communal level and vice versa. Any inclusive model would meet the needs of each and all individuals of society and satisfies individual resilience, only if it follows a one-to-one stakeholders' comprehension and communication. Such a model enables both identifying their real needs and problems and foreseeing their future needs in probable disastrous situations. Secondly, based on the Durkheimian theory of society, we cannot simply take community resilience like a bijective (one-to-one correspondence) function of individual resilience. That is, the study of resilience, as one feature of a community, is not equal to study of individual resilience. For example, after a great depression in a society, it is not guaranteed that this communal depression will be removed after a successful recovery of all the individuals of that society, and it may take longer for the community to rebound the connections among the individuals to produce its communal level functions. It might be said that changes in society are greater and more lasting than changes in individual levels, and usually, it takes time to return society to the primary status before a disaster. Moreover, it is not plausible to only consider one community resilience in each society because there are many sub-communities in a given society. Each sub-community has different values and capabilities, and some have overlap as well. Thus, it seems that any comprehensive model of community resilience must be both individual-sensitive and communal-sensitive and also consider all the major communities in a society. Being individual-sensitive, which requires consideration of the needs of each and all individuals in the community, is equivalent to the human-centric approach, and therefore requires cognitive empathy, as discussed above. On the other hand, being communal-sensitive requires even deeper empathy. Being communal-sensitive requires two criteria: First, one needs to feel like an individual in that community. Secondly, it is essential to evoke the same feeling of the members of that community and maintain it for a long time in order to enable underrating the social fact. For example, one might understand what it means to be poor in a rich family. In such cases, it is probable that the poor person is not able to afford charges and always needs to borrow money from family members. However, living in a poor community has a different sense, which is not equal to the former feelings. In a poor community, in difficult situations, there is nobody to rely on, and this makes a great difference. Thus, to understand what it is like to live in a poor society, one needs to fully know and deeply experience the same feeling. Empathy provides this chance through participant observations. In this method, by applying conative empathy, you would act like a member of that community, and after a while, you will gain the same affections of that community (i.e., affective empathy), and it finally leads to understanding like a member of that [24] [25] community (i.e., cognitive empathy). That is, you need to empathically be involved in those communities and put yourself in their shoes for a while so you can also understand the socialand communal-level facts which are not equal to the individual ones. 2.3 Being Justice-Oriented An inclusive community resilience aims at justice, which can be accounted for in three major moral approaches, all of which require three kinds of cognitive, affective, and conative empathy. Community resilience is committed to bringing about human well-being, which refers to the well-being of each and all human individuals irrespective of their gender, sex, race, education, financial status, etc. Studies in vulnerability assessment of the communities have revealed that the socially vulnerable population experience higher hardship from natural hazards . This has been shown to be rooted in individuals' higher exposure to the threats and their lower ability to tolerate the negative impacts . The social inequities in the societal impacts of natural hazards suggest that current approaches have failed to meet the needs of the affected communities . This highlights the importance of incorporating justice in designing resilient infrastructure systems. Therefore, an engineering system would be resilient only if it aims at justice and equally considers each and all individuals. Three major moral accounts can be implemented for including justice in the resilience of the sociotechnical system: First, Virtue ethics, which emphasize the subjective moral virtues; secondly, Deontology (or Kantian Ethics), which emphasize the duties and universal moral rules (i.e., categorical imperatives); and thirdly, consequentialism (or utilitarianism) which refers to the consequences of actions. Given that community resilience requires each and all individuals to be helped, there could be three approaches to the necessity of such a humanistic consideration. First, according to Virtue ethics, community resilience has to be humanistic because helping other people comes from the human virtue of being benevolent and compassionate (i.e., referring to an agent's subjective moral character) . Second, Kantian Ethics holds that we must help others because it is a universal moral rule, no matter what the characteristics of the agent are or what the consequence of the act could be . Third, utilitarians believe that it is essential that each and all individuals are considered and assisted in a natural hazard because it ultimately maximizes the well-being of the community . All these approaches highlight empathy in community resilience. The first two accounts lead to the Golden Rule, which says, "Others are to be treated by me as we would wish them to treat me" . This, in turn, leads to conative empathy, which refers to the empathetic treatment of people based on cognitive and affective empathy. They both require human beings to think of other people like themselves, either as virtuous or as a moral duty. Moreover, the last utilitarian account also requires people to treat others fairly and empathetically without considering the actions as a kind of human virtuous or as a moral duty. According to utilitarianism, we need to treat others as we wished to be treated, empathetically, because it finally guarantees our ultimate interests in a social system. It holds that an engineering system would be effectively resilient in the long term, only if it really cares about justice. In other words, equity between individuals ultimately maximizes well-being for all the individuals, including those who are not affected too much by the disasters . 2.4 Being Values-Based Consistent An inclusive, resilient system ought to be values-based consistent, while a values-based consistency will be fulfilled by cognitive empathy. It is largely considered that a resilient system has to be adaptive and must learn how to foresee the probable impacts during and after disasters. Foreseeing the potential impacts due to the disasters should be implemented in the engineering of infrastructure systems. However, achieving this objective would only be effectively obtained if it follows a value consistency between the designers and stakeholders. The designers and stakeholders, including both human resources of the infrastructure systems and human users, have different values and conceptualizations [26][27] [28] [29] [30] [31] [32] [33] [32] which have to be diagnosed, translated into a common language, and compromised. The different interpretation of a problem from different points of view, if not considered, prevents the outcome systems from achieving their objective in meeting the needs of individuals in the affected community. Such inconsistency in the fundamental value-level might cause some additional problems for the resiliency and sustainability of the system. For example, if the designers for local public transportation translate the ultimate goal of the system in terms of "expedition and speed," which is not committed to the "whole accessibility," the system would fail to meet the needs of the users, and this would also negatively affect the social justice. Value consistency needs an understanding of other minds. Values include some conscious and unconscious concepts and beliefs in humans' minds, which are not necessarily communicated explicitly or correctly between the stakeholders. Discovering the correct formulation of all stakeholders requires the epistemic tool of cognitive empathy. This tool provides engineers with an understanding of the stakeholders' minds to enable them to incorporate those values in the resilience design of infrastructure systems. References 1. Cuff, B.M.P.; Brown, S.J.; Taylor, L.; Howat, D.J. Empathy: A review of the concept. Emot. Rev. 2016, 8, 144–153. 2. Shaw, K.; Dermoudy, J. Engendering an Empathy for Software Engineering. Conf. Res. Pract. Inf. Technol. Ser. 2005, 42, 135–144. 3. Bielefeldt, A.R. Is Engineering about Caring for and Helping Others? In Focus on Educational Research: Practices, Challenges and Perspectives; Hernandez, B., Ed.; Nova Science Publishers: Hauppauge, NY, USA, 2017. 4. Gunckel, K.L.; Tolbert, S. The imperative to move toward a dimension of care in engineering education. J. Res. Sci. Teach. 2018, 55, 938–961. 5. Walther, J.; Brewer, M.A.; Sochacka, N.W.; Miller, S.E. Empathy and engineering formation. J. Eng. Educ. 2020, 109, 11–33. 6. Strobel, J.; Hess, J.; Pan, R.; Morris, C.A.W. Empathy and care within engineering: Qualitative perspectives from engineering faculty and practicing engineers. Eng. Stud. 2013, 5, 137–159. 7. Hess, J.L.; Sprowl, J.E.; Pan, R.; Dyehouse, M.; Morris, C.A.W.; Strobel, J. Empathy and caring as conceptualized inside and outside of engineering: Extensive literature review and faculty focus group analyses. ASEE Annu. Conf. Expo. Conf. Proc. 2012. 8. Hess, J.L.; Strobel, J.; Pan, R. Voices from the workplace: Practitioners' perspectives on the role of empathy and care within engineering. Eng. Stud. 2016, 8, 212–242. 9. Walther, J.; Miller, S.E.; Sochacka, N.W. A Model of Empathy in Engineering as a Core Skill, Practice Orientation, and Professional Way of Being. J. Eng. Educ. 2017, 106, 123–148. 10. Pappa, C.I.; Reinhold, S.; Pittich, D.; Vogel-Heuser, B.; Strobel, J. Engineers' job-related perceptions of empathy in Germany. In Proceedings of the 2020 IEEE Global Engineering Education Conference (EDUCON), Porto, Portugal, 27–30 April 2020; pp. 741–745. 11. Goetz, J.L.; Keltner, D.; Simon-Thomas, E. Compassion: An evolutionary analysis and empirical review. Psychol. Bull. 2010, 136, 351–374. 12. Stueber, K. Empathy; The Stanford Encyclopedia of Philosophy: Stanford, CA, USA, 2018. 13. Wispé, L. The distinction between sympathy and empathy: To call forth a concept, a word is needed. J. Pers. Soc. Psychol. 1986, 50, 314–321. 14. Ickes, W. Empathic Accuracy. J. Pers. 1993, 61, 587–610. 15. Clark, A. Empathy and Sympathy: Therapeutic Distinctions in Counseling. J. Ment. Heal. Couns. 2010, 32, 95–101. 16. Hein, G.; Singer, T. I feel how you feel but not always: The empathic brain and its modulation. Curr. Opin. Neurobiol. 2008, 18, 153–158. 17. Decety, J.; Lamm, C. Human empathy through the lens of social neuroscience. Sci. World J. 2006, 6, 1146–1163. 18. Albiero, P.; Matricardi, G.; Speltri, D.; Toso, D. The assessment of empathy in adolescence: A contribution to the Italian validation of the 'Basic Empathy Scale'. J. Adolesc. 2009, 32, 393–408. 19. Tamayo, C.A.; Rizkalla, M.N.; Henderson, K.K. Cognitive, Behavioral and Emotional Empathy in Pharmacy Students: Targeting Programs for Curriculum Modification. Front. Pharmacol. 2016, 7, 96. 20. Barker, R.L. The Social Work Dictionary; NASW Press: Washington, DC, USA, 1995. 21. Davis, M.H. Empathy: A Social Psychological Approach; Westview Press: Boulder, CO, USA, 1994. 22. Oliveira-Silva, P.; Gonçalves, O.F. Responding empathically: A question of heart, not a question of skin. Appl. Retrieved from https://encyclopedia.pub/11378 Psychophysiol. Biofeedback 2011, 36, 201–207. 23. Doorn, N.; Gardoni, P.; Murphy, C. A multidisciplinary definition and evaluation of resilience: The role of social justice in defining resilience. Sustain. Resilient Infrastruct. 2018, 9689, 1–12. 24. Giddens, A. Introduction to Sociology; Norton: New York, NY, USA, 1991. 25. Durkheim, E. The Rules of Sociological Method: And Selected Texts on Sociology and Its Method; Springer: Berlin/Heidelberg, Germany, 1982. 26. Coleman, N.; Esmalian, A.; Mostafavi, A. Anatomy of Susceptibility for Shelter-in-Place Households Facing Infrastructure Service Disruptions Caused by Natural Hazards. Int. J. Disaster Risk Reduct. 2020, 50, 101875. 27. Peacock, W.G.; Ragsdale, A.K. Social systems, ecological networks and disasters: Toward a socio-political ecology of disasters. In Hurricane Andrew: Ethnicity, Gender, and the Sociology of Disasters; Routledge: New York, NY, USA, 1997; pp. 20–35. ISBN 9780203351628. 28. Lindell, M.K. Fundamentals of Emergency Management; FEMA: Washington, DC, USA, 2006. 29. Community Resilience Planning Guide. Community Resilience Planning Guide for Buildings and Infrastructure Systems, Volume II; National Institute of Standards and Technology: Gaithersburh, MD, USA, 2015; Volume 2, p. 260. 30. Hursthouse, R.; Glen Pettigrove, G. Virtue Ethics; The Stanford Encyclopedia of Philosophy: Stanford, CA, USA, 2018. 31. Alexander, L.; Moore, M. Deontological Ethics; The Stanford Encyclopedia of Philosophy: Stanford, CA, USA, 2007. 32. Sinnott-Armstrong, W. Consequentialism; The Stanford Encyclopedia of Philosophy: Stanford, CA, USA, 2011. 33. Finnis, J. Aquinas' Moral, Political, and Legal Philosophy; The Stanford Encyclopedia of Philosophy: Stanford, CA, USA, 2005. Keywords empathy;empathic design;Community Resilience;Sustainability;Justice


Philosophy

23 Philosophia Philosophical Quarterly of Israel ISSN 0048-3893 Philosophia DOI 10.1007/s11406-017-9873-5 Sensitivity has Multiple Heterogeneity Problems: a Reply to Wallbridge Guido Melchior 1 23 Your article is published under the Creative Commons Attribution license which allows users to read, copy, distribute and make derivative works, as long as the author of the original work is cited. You may selfarchive this article on your own website, an institutional repository or funder's repository and make it publicly available immediately. Sensitivity has Multiple Heterogeneity Problems: a Reply to Wallbridge Guido Melchior1 Received: 25 January 2017 /Revised: 10 June 2017 /Accepted: 16 June 2017 # The Author(s) 2017. This article is an open access publication Abstract In this paper, I defend the heterogeneity problem for sensitivity accounts of knowledge against an objection that has been recently proposed by Wallbridge in Philosophia (2016b). I argue in (Melchior in Episteme, 12(4), 479–496, 2015) that sensitivity accounts of knowledge face a heterogeneity problem when it comes to higher-level knowledge about the truth of one's own beliefs. Beliefs in weaker higher-level propositions are insensitive, but beliefs in stronger higher-level propositions are sensitive. The resulting picture that we can know the stronger propositions without being in a position to know the weaker propositions is too heterogeneous to be plausible. Wallbridge objects that there is no heterogeneity problem because beliefs in the weaker higher-level propositions are also sensitive. I argue against Wallbridge that the heterogeneity problem is not solved but only displaced. Only some beliefs in the weaker higher-level propositions are sensitive. I conclude that the heterogeneity problem is one of a family of instability problems that sensitivity accounts of knowledge face and that Wallbridge's account raises a further problem of this kind. Keywords Sensitivity . Higher-level knowledge . Bootstrapping . Heterogeneity problem 1 The Heterogeneity Problem Nozick (1981) defines that a belief that p formed via method M is sensitive iff in the nearest possible worlds where p is false and where S uses M for determining Philosophia DOI 10.1007/s11406-017-9873-5 * Guido Melchior firstname.lastname@example.com 1 Department of Philosophy, University of Graz, Heinrichstrasse 26/5, 8010 Graz, Austria whether p (or ¬p) is true, S does not believe via M that p. Nozick argues that sensitivity is necessary for knowing. I argue in (Melchior 2015) that sensitivity accounts of knowledge face a particular problem when it comes to higher-level knowledge. Beliefs that one does not falsely believe that p are insensitive if their underlying formal structure is ¬(B(p) ∧ ¬p). I label these beliefs B(d), since they have the formal structure of a disjunction. However, beliefs that one truly beliefs that p, with the underlying formal structure B(p) ∧ p, are sensitive if the belief that p is sensitive. Moreover, beliefs that one's belief that p is not false with the formal structure B(p) ∧ ¬¬p are also sensitive if the belief that p is sensitive. I label these beliefs B(c) since they are beliefs in a conjunction. Notably, c is a stronger proposition than d. Thus, sensitivity accounts of knowledge have it that we are in a position to know the stronger proposition c without being in a position to know the weaker proposition d. This outcome is highly implausible. I labeled this problem the heterogeneity problem for sensitivity accounts. This heterogeneity problem marks a further step in a discussion about sensitivity and higher-level knowledge. Sosa (1999) and Vogel (2000) first pointed out that beliefs in d are insensitive. Sosa argued that it is an implausible instance of closure failure that one can know that p without knowing that d since p is a stronger proposition than d. Vogel concludes more directly that sensitivity accounts of knowledge preclude us from having any higher-level knowledge since we cannot know that d. Becker (2006) and Salerno (2010) then argued against Vogel that we can have higher-level knowledge according to sensitivity accounts since beliefs in c can be sensitive. The heterogeneity problem arises if one combines the orthodox views that beliefs in c can be sensitive but that beliefs in d cannot. Wallbridge (2016a) opposes these orthodox views by arguing that even beliefs in d turn out to be sensitive if we properly take the belief forming method into account. Based on this line of argumentation, Wallbridge (2016b) continues to argue that sensitivity does not suffer from any heterogeneity problem. I will show that his objection is doomed to fail. Wallbridge is partly right since some beliefs in d are sensitive. However, I will argue that some other beliefs in d are insensitive. Thus, Wallbridge's account does not solve the heterogeneity problem; rather, it raises an additional problem of instability for sensitivity accounts. Or so I will argue. Before analyzing Wallbridge's objection, let me clarify my overall position on sensitivity. Given the objections that I raise against sensitivity accounts of knowledge, one might think that I am a convinced critic of the sensitivity principle. On the contrary, I find it intuitively appealing and I think that it deserves a crucial role in epistemology. However, I also think that 'knowledge' is the wrong concept for applying it. In Knowing and Checking (book manuscript), I argue that sensitivity is necessary for checking (and similar epistemic enterprises like testing), but not for knowing. Thus, sensitivity marks a crucial distinction between knowing and checking. To be more explicit, I suggest that S cannot check whether p is true via method M if, in the nearest possible worlds where p is false and where S uses M for determining whether p is true, M indicates that p. Moreover, the sensitivity account of checking that I elaborate in Knowing and Checking does not suffer from those kinds of problems that I pose for sensitivity accounts of knowledge. Thus, there is nothing wrong with sensitivity, only with sensitivity accounts of knowledge. Philosophia 2 Wallbridge's Case and Alternative Cases Wallbridge (2016a, b) argues against orthodoxy that higher-level beliefs in d can be sensitive. He does so by discussing Vogel's Omar case: OMAR You see your long-time friend Omar, who is a perfectly decent and straightforward sort of person. Noticing his shiny white footwear, you say, BNice shoes, Omar, are they new?^ Omar replies, BYes, I bought them yesterday.^ You know that Omar has new shoes, and that you believe that Omar has new shoes. You also know, if you think about it, that you don't falsely believe that Omar has new shoes. (Wallbridge 2016b) Wallbridge argues that my belief that I do not falsely believe that Omar got new shoes is sensitive if we take the belief-forming method into account as Nozick suggests. We can assume that Omar is a sensitive informant about his shoes since Vogel claims that I know that Omar has new shoes which implies, on a sensitivity account of knowledge, that this belief is sensitive. Wallbridge argues that in the nearest possible worlds where I falsely believe that Omar has new shoes, I believe it on a different basis than Omar's testimony, since Omar is a sensitive informant about his shoes. For example, I might believe it on the basis of Lila's testimony who is a very unreliable informant about the footwear of her friends. Thus, in the actual world, I believe that Omar has new shoes based on Omar's testimony but on a different basis in the nearest possible worlds where I falsely believe that Omar has new shoes. Crucially, my belief that I do not falsely believe that Omar has new shoes is sensitive if in the nearest possible worlds where I falsely believe that Omar has new shoes and where I use the same method as in the actual world, I do not believe via this method that I do not falsely believe that Omar has new shoes. This sensitivity condition is actually fulfilled because Omar is a sensitive informant about his shoes. In the nearest possible worlds where I falsely believe that Omar has new shoes and where I ask Omar whether he has new shoes, I come to believe that he does not have new shoes. Wallbridge's argumentation presumably goes through if we fill in the details as he suggests, i.e. if we assume that in the nearest possible worlds where I falsely believe that Omar has new shoes, I believe it on a different basis than I believe it in the actual world. But note that this crucially depends on how the details are filled in. Take the following alternative case: ROBINSON CRUSOE Robinson Crusoe and Freitag are the only inhabitants of a small island. They make their cloth out of palm leaves and lianas. One day, Freitag sees his longtime friend Robinson Crusoe, who is a perfectly decent and straightforward sort Philosophia of person. Noticing his newly bound footwear, Freitag says, BNice shoes, Robinson! Are they new?^ Robinson replies, BYes, I made them yesterday.^ Wallbridge's interpretation of OMAR depends on the assumption that there are other methods available for believing that Omar has new shoes and that worlds where I falsely believe that Omar has new shoes via some other method are closer than the nearest possible worlds where I falsely believe via Omar's testimony that he has new shoes. However, this is not the case in ROBINSON CRUSOE, where presumably there is no other method available, for example testimony from someone else, that could deliver that Robinson Crusoe has new shoes beside Robinson's testimony. Robinson Crusoe might be a very decent person such that possible worlds where he falsely reports that he has new shoes are very remote. Nevertheless, any of these remote possible worlds is still closer than possible worlds where Freitag believes via a different method than Robinson's testimony that Robinson has new shoes. Thus, in the nearest possible worlds where Freitag falsely believes that Robinson has new shoes, he believes it via Robinson's testimony. But in this case, in the nearest possible worlds where Freitag falsely believes that Robinson has new shoes and uses the same method as in the actual world, he comes to believe that he does not falsely believe that Robinson has new shoes. Thus, Freitag's belief that he does not falsely believe that Robinson has new shoes is insensitive. Take a second example: MORPHELIA Sigmund, Morphelia's psychotherapist, asks her about her dreams last night. Morphelia is a perfectly decent and straightforward sort of person. Morphelia tells Sigmund that she dreamt that five green eagles picked her up and flew her into an orange classroom. Even if Morphelia is a very decent and straightforward person, the nearest possible worlds where Sigmund falsely believes that Morphelia dreamt five green eagles picked her up and flew her into an orange classroom are such that he believes it via testimony from Morphelia. This is so because possible worlds where someone else makes reports to Sigmund about Morphelia's dreams (and especially that Morphelia had this particular dream) are presumably modally even more remote than worlds where Morphelia made a false report about her dreams. Thus, in the nearest possible worlds where Sigmund falsely believes that Morphelia dreamt last night that five green eagles picked her up and flew her into an orange classroom and where he uses the same method as in the actual world, he will believe via this method that he does not falsely believe that Morphelia dreamt last night that five green eagles picked her up and flew her into an orange classroom. Thus, Sigmund's belief is insensitive. Freitag's belief and Sigmund's belief are both insensitive because possible worlds where they falsely believe the target propositions via the same method as in the actual world are closer than possible worlds where they falsely believe it via a different method. In ROBINSON, this is the case due to social isolation, viz. under normal circumstances propositions like 'S has new shoes' can typically be falsely believed via different sources than S's testimony. In contrast, propositions about the content of S's Philosophia dreams are normally only believed via S's testimony. In some cases, like OMAR, beliefs in d might be sensitive as Wallbridge suggests, but, in some other cases, beliefs in d are insensitive. Let us have a more systematic look at the issue. Whether beliefs in d are sensitive depends on whether the following Wallbridge-condition W is fulfilled: Wallbridge's condition S's belief that she does not falsely believe that p formed via method M is sensitive iff the following Wallbridge condition W is fulfilled.W: Possible worlds where S falsely believes that p via some other method M* are closer than the nearest possible worlds where S falsely believes that p via M. S's belief that p formed via M is sensitive iff in the nearest possible worlds where p is false and S uses M for determining whether p, S does not believe that p via M. W is fulfilled iff in the nearest possible worlds where S falsely believes that p, S does so via M*. Thus, sensitivity is a feature of beliefs formed via method M whereas condition W characterizes a relation between M and alternative methods M*. A belief that p formed via M can be sensitive yet fail to fulfill condition W. If S's belief that p via M is sensitive then there is a neighborhood of possible worlds where p is false and where S does not believe that p via M. If in this neighborhood there exists a method M* via which S falsely believes that p, then W is fulfilled, otherwise not. Whether there is such a method M* is contingent. Thus, the connection between sensitivity and condition W is contingent. The orthodox view about sensitivity and higher-level beliefs has it that beliefs in d are insensitive. The heterogeneity problem is based on the assumption that beliefs in d are insensitive but that beliefs in stronger propositions c are sensitive (if the basic belief that p is sensitive). Wallbridge is presumably right that some beliefs in d are sensitive. He suggests that the heterogeneity problem vanishes because beliefs in c and in d can be sensitive. We saw that he is mistaken. Some beliefs in d can be sensitive but others not. Consequently, the heterogeneity problem has to be reformulated as follows. Beliefs in c are sensitive if the basic belief that p is sensitive. Some beliefs in the weaker proposition d are sensitive, some others are not. Where does this leave us? Epistemically, there is no crucial difference between cases like OMAR, ROBINSON or MORPHELIA. Thus, I do not see why I should be epistemically in a better position concerning Omar's shoes than Freitag is concerning Robinson's shoes or Sigmund is concerning Morphelia's dreams. Consequently, it is problematic to evaluate these cases differently and to claim that we know in OMAR but not in ROBINSON or MORPHELIA. Even if Wallbridge's analysis is correct that some beliefs in d are sensitive, some other beliefs in d are insensitive. Thus, Wallbridge does not solve the heterogeneity problem, rather he merely displaces it. 3 Conclusion The heterogeneity problem arises because higher-level beliefs in higher-level proposition d are insensitive but higher-level beliefs in stronger higher-level Philosophia propositions c are sensitive. Thus, according to sensitivity accounts of knowledge, we have stronger higher-level knowledge but lack weaker higher-level knowledge which is a highly unsatisfactory outcome. Importantly, the heterogeneity problem is only one instance of a family of problems for sensitivity accounts that point towards the fact that sensitivity is too unstable over propositions and methods for being a criterion for knowledge. Nozick (1981) already noted that beliefs in the denial of the skeptical hypothesis, ¬sh, are insensitive, but that beliefs in conjunctions of ¬sh and ordinary external world propositions, ¬sh ∧ p, are sensitive. For example, my belief that I am not a deceived brain in a vat (BIV) is insensitive because in the nearest possible worlds where I am a deceived BIV I believe that I am not a deceived BIV. However, my belief that there is a computer in front of me and that I am not a deceived BIV is sensitive. In the nearest possible worlds where this conjunction is false there is no computer in front of me and I am still not a deceived BIV. However, in these possible worlds, I do not believe this conjunction because I fail to believe the conjunct that there is a computer in front of me. Thus, sensitivity accounts of knowledge are committed to accept that we can know that ¬sh ∧ p although we are not in a position to know that ¬sh. This outcome is counterintuitive. In this case, sensitivity is too unstable with regard to closely related proposition ¬sh and ¬sh ∧ p. In this respect, this problem is closely related to the heterogeneity problem of knowing c but not knowing d.1 Wallbridge aims at showing that beliefs in the weaker propositions d are sensitive and that they can, therefore, constitute knowledge. If his point goes through for any belief in d, then the heterogeneity problem could be solved. However, it does not. In fact, his account raises an additional problem for sensitivity. If one grants his analysis of OMAR, then some beliefs in d are sensitive as he suggests, but some others are insensitive. This problem is a further instance of the instability problems to which the heterogeneity problem belongs. If Wallbridge's analysis is correct, then one is forced to reformulate the heterogeneity problem but Wallbridge does not solve this problem, without raising a new problem of a similar kind. In fact, Wallbridge's analysis offers further evidence that the instability problems are the crucial problems for sensitivity accounts of knowledge. Acknowledgements Open access funding provided by University of Graz. I am indebted to Wes Siscoe for helpful comments on this paper. The research was funded by the Austrian Science Fund (FWF): P 28884-G24. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and 1 I argue in (Melchior 2014a) that DeRose's (1995, 2010) indirect sensitivity account also suffers from this problem. DeRose uses the sensitivity principle for explaining our intuitions about knowledge, although he does not directly build a sensitivity condition into the concept of knowledge. DeRose's account fails because sensitivity cannot explain our intuitions about knowing that the skeptical hypotheses are false. Intuitively, if we do not know that ¬sh, then we also do not know that ¬sh ∧ p. However, DeRose's indirect sensitivity account predicts that we think that we do not know that ¬sh, but think that we know that ¬sh ∧ p. Moreover, I argue in (Melchior 2014b) that sensitivity accounts also face a particular generality-problem when it comes to higherlevel knowledge of c. One might object that the generality problem is everybody's problem but other externalistic accounts such as safety or process reliabilism at least avoid this particular version of it. With the heterogeneity problem and the problem of knowing a conjunction without knowing one of its conjuncts, sensitivity is too unstable concerning the involved propositions. As for the generality problem, it is particularly unstable concerning the method in question. Philosophia reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. References Becker, K. (2006). Is counterfactual reliabilism compatible with higher-level knowledge? Dialectica, 60(1), 79–84. DeRose, K. (1995). Solving the skeptical problem. The Philosophical Review, 104(1), 1–52. DeRose, K. (2010). Insensitivity is back, baby! Philosophical Perspectives, 24, 161–187. Melchior, G. (2014a). Skepticism: the hard problem for indirect sensitivity accounts. Erkenntnis, 79, 45–54. Melchior, G. (2014b). A generality problem for bootstrapping and sensitivity. Croatian Journal of Philosophy, 14, 31–47. Melchior, G. (2015). The heterogeneity problem for sensitivity accounts. Episteme, 12(4), 479–496. Nozick, R. (1981). Philosophical explanations. Massachusetts: Harvard University Press. Salerno, J. (2010). Truth tracking and the problem of reflective knowledge. In J. K. Campbell, M. O'Rourke, & H. S. Silverstein (Eds.), Knowledge and skepticism (pp. 72–81). Cambridge: The MIT Press. Sosa, E. (1999). How to defeat opposition to Moore. Philosophical Perspectives, 13(s13), 137–149. Vogel, J. (2000). Reliabilism leveled. Journal of Philosophy, 97(11), 602–623. Wallbridge, K. (2016a). Sensitivity and higher-order knowledge. Pacific Philosophical Quarterly, 97(2). doi:10.1111/papq.12164. Wallbridge, K. (2016b). Sensitivity hasn't got a heterogeneity problem. A reply to Melchior. Philosophia. doi:10.1007/s11406-016-9782-z. Philosophia