Studies in History

Stud. Hist. Phil. Sci. 37 (2006) 118–131

www.elsevier.com/locate/shpsa

and Philosophyof Science

The ontology of artefacts: the hard problem

Wybo Houkes, Anthonie Meijers

Eindhoven University of Technology, Section of Philosophy and Ethics of Technology, PO Box 513,

NL-5600 MB Eindhoven, The Netherlands

Abstract

We examine to what extent an adequate ontology of technical artefacts can be based on existinggeneral accounts of the relation between higher-order objects and their material basis. We considertwo of these accounts: supervenience and constitution. We take as our starting point the thesis thatartefacts have a ‘dual nature’, that is, that they are both material bodies and functional objects. Wepresent two criteria for an adequate ontology of artefacts, ‘Underdetermination’ (UD) and ‘Realiz-ability Constraints’ (RC), which address aspects of the dual nature thesis. Assessing supervenienceaccounts, we find them either wanting with respect to these criteria or insufficiently informative.Next, we argue that a recent application of Lynne Rudder Baker’s constitution view to artefacts can-not (yet) meet our criteria, although the broader view leaves room for improvement. Based on ourevaluation of the most promising candidates, we conclude that so far general metaphysical views failto address the most salient features of artefacts. Although they can account for the fact that artefactshave a ‘dual nature’, they do not offer the conceptual resources needed to describe the relationbetween these natures; this relation raises a hard problem in metaphysics.� 2005 Elsevier Ltd. All rights reserved.

Keywords: Metaphysics; Artefact; Supervenience; Constitution; Underdetermination

1. Introduction: the dual nature of technical artefacts

In this paper, we reflect on technical artefacts from an ontological perspective. Ourstarting point is the thesis that artefacts have a ‘dual nature’ (Kroes & Meijers, 2006):

0039-3681/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.shpsa.2005.12.013

E-mail addresses: w.n.houkes@tue.nl (W. N. Houkes), a.w.m.meijers@tue.nl (A. W. M. Meijers).

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technical artefacts, that is, the products designed by engineers for practical purposes, areboth physical bodies that have geometrical, physical, and chemical characteristics, andfunctional objects that have an intrinsic relation to mental states and intentional actions.This thesis can be developed in different directions, for example, conceptually, by connect-ing the two ‘natures’ in a coherent conceptualisation (Kroes, 2006), or epistemically, byarguing that functional knowledge cannot be reduced to knowledge of physical character-istics (Houkes, 2006).

Whatever the merits of these enterprises, and however pressing the questions they raisemay be, they neglect one aspect of the dual nature thesis: it quite clearly and unabashedlyaddresses the ontology of artefacts. It reflects a metaphysical view about the nature of arte-facts, namely that it is twofold.

In this paper, we look at the dual nature thesis from the standpoint of metaphysics.From this angle, some surprising features can be discerned. For one thing, the metaphysicsof artefacts does not suffer from the complete neglect that plagues other parts of the phi-losophy of artefacts. Both Aristotle and Heidegger can be interpreted as providing onto-logical views on artefacts; more recently Van Inwagen (1990), Wiggins (2001), and Baker(2004), all well known contributors to general metaphysics, have constructed ontologicalaccounts of artefacts and have discussed the ontological respectability of artefacts. More-over, some hotly debated topics in metaphysics use artefacts as prime examples, if notfocussing explicitly on them. Theseus’s ship and Goliath (and/or Lumpl) are both artefactsand metaphysical conundrums.

We do not contribute directly to these debates. We assume, following Baker (2004),that artefacts are ontologically respectable—to put it simply, that artefacts exist. Ourprimary aim in this paper is to examine whether the dual nature thesis, read ontolog-ically, is compatible with general accounts of the relation between higher-order objectsand their material basis. More precisely, we examine whether this relation can, in thecase of artefacts, be understood as one of either supervenience or constitution. In Sec-tion 2, we present two non-arbitrary criteria for an adequate ontology of artefacts.These criteria, ‘Underdetermination’ and ‘Realizability Constraints’, are intimately con-nected to the dual nature thesis; thus, they are an integral part of what drives ourinterest in the ontology of artefacts. In Section 3, we examine whether supervenienceaccounts meet these criteria. There are obvious similarities between the dual naturethesis and ontological problems in the philosophy of mind; therefore, it makes prima

facie sense to suppose that some supervenience account, although perhaps primarilydeveloped to solve the latter problems, presents a defensible ontology of artefacts.We argue that, despite favourable first impressions, supervenience does not fit the bill.In Section 4, we turn to another general metaphysical account, Lynne Rudder Baker’sconstitution view. We argue that, in its present form, it cannot meet our criteria for anadequate ontology of artefacts, although, unlike supervenience accounts, the constitu-tion view has been modified to apply specifically to artefacts and can be modified fur-ther still. This brings us to our general conclusions, in Section 5. Based on ourevaluation of the prima facie most promising candidates, we conclude that existingmetaphysical views fail to address the most salient features of artefacts—as expressedin our criteria of adequacy. Although some general views can account for the fact thatartefacts have a ‘dual nature’, they do not offer the conceptual resources needed todescribe the relation between these natures; this relation raises a hard problem inmetaphysics.

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2. Criteria for an ontology of artefacts

Before evaluating whether existing general metaphysical views of the relation betweenhigher-order objects and their material basis can be applied to artefacts, let us review thecriteria for a successful application. In this section, we present two aspects of the ontolog-ical relation between artefacts and their material basis1 that we consider to be of suchimportance that they form basic criteria for an ontology of artefacts.

These two criteria have not been chosen haphazardly; they do more than make expli-cit the appeal to intuition that seems inevitable in metaphysics. Both criteria are centralto the practice of designing artefacts or selecting objects for practical use, even thoughthey might not be delineated explicitly there. Furthermore, both criteria stem from theoverriding concern to present a philosophical analysis of artefacts as objects with (i)structural (that is, geometric, physical, chemical) characteristics and (ii) functional char-acteristics which have an intrinsic relation to mental attitudes and intentional actions; inshort, the criteria stem from our concern of analysing the dual nature of technicalartefacts.

Having said this, we propose the following two criteria for an adequate ontology oftechnical artefacts:

1 Sinadhere2 Re

‘Flat’whichunderdwith th

Underdetermination

An adequate ontology of artefacts should accommodate a two-way underdetermin-ation between artefacts and their material basis: an artefact type, as a functionaltype, is multiply realizable2 in material structures or systems, while a given materialbasis can realize a variety of functions.

Realizability constraints

An adequate ontology of artefacts should accommodate and constrain the two-wayunderdetermination of artefacts and their material basis. There are many kinds ofpractical inferences from functional to structural statements and vice versa. Some rel-evant reasoning patterns in artefact use and design are:

– the selection and development of materials given a particular function, for exam-ple, lightweight composites for building airplanes (‘function-to-structure’).

– studies on possible ways of re-using materials, for example, depleted uranium asammunition or worn car tires as curb stones (‘structure-to-function’).

– systematic searches for the cause of failure in cases of repair or malfunctioning, forexample, the analysis of airplane crashes. Conclusions can be statements abouthuman actions or about the artefact’s structure. In the latter case we reason fromthe artefact’s function to how its structure should behave.

ce the content of the criteria is intended to be neutral with respect to the frameworks under review,nts of supervenience may interpret the relata as ‘functional property’ and ‘physical property’ respectively.cently, the ‘realization’ relation has come under critical scrutiny. Gillett (2002) distinguishes a standard,notion, in which the relata are properties instantiated in the same object, from a ‘dimensioned’ notion, inthe relata are properties instantiated in different individuals. Strictly speaking, neither notion explicates ouretermination relation, which relates individuals, not properties. The dimensioned notion seems compatiblee constitution view examined in Section 4, but we lack the space for a further analysis.

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These two criteria provide important commentaries on the thesis that artefacts have a dualnature. Taken literally, this thesis requires any ontology of artefacts to have two ‘concep-tual components’, irreducible to one another: one set of concepts describing the artefactand another describing their material basis. However, to put it somewhat whimsically, thisrelation also has a dual nature: it is both flexible and rigid. (UD) reflects its flexibility sinceit says that artefact and material basis do not have a one-on-one relation; (RC) reflects itsrigidity since it says that information about the artefact yields some information about itsmaterial basis and vice versa. The ontological problem presented by artefacts resides intheir dual nature as such and in the duality of the relation between the two natures.

In addition, the following brief remarks about both criteria can be made. Underdeter-mination (UD) is similar to a familiar point in the philosophy of mind: the multiple real-izability of mental states and/or properties. Furthermore, many theories of function havesought to capture the physics-to-function underdetermination in terms of a distinctionbetween the proper function of an artefact and accidental features or functions, thatis, other roles that it may play. We can use airplanes for flying (proper function), butalso as museum pieces (accidental function). One may have doubts about the fertilityof this conceptual strategy (Houkes & Vermaas, 2004); we just note that our route isdifferent: we consider the relation between artefact and material basis without analysingthe notion of function. Finally, by introducing Realizability Constraints (RC), we takereasoning or, more broadly, epistemic concerns as a guide to ontology. However, takingthis guide does not, in our opinion, presuppose a contentious (meta-)philosophical view.Function–structure reasoning patterns are highly useful and can be intuitively sound. Itwould be passing strange if these patterns were not, in some minimal way, matched byontological constraints.

3. Supervenience

The notion of supervenience has become a central notion in the philosophy of mind inrecent decades, where it is used to develop an account of the relation between the mentaland the physical that is non-reductionist. According to Jaegwon Kim, three different ideasare associated with the concept of supervenience (Kim, 1994, p. 576):

� the co-variation of properties between the subvenient and supervenient level. If twoentities are indiscernible in their base properties, they must be indiscernible in theirsupervenient properties. The subvenient base consists of physical/chemical/biolog-ical structures and properties, the supervenient level of mental properties, includingconsciousness.

� dependence. Supervenient properties are dependent on or determined by the baseproperties.Mental properties are, however, multiply realizable in physical structures.

� non-reducibility. Supervenient properties are not reducible to subvenient properties.

The basic idea of supervenience is that physical duplicates are necessarily psychologicalduplicates. No two things that are physically alike can be mentally different. There aretwo pairs of notions of supervenience around in the literature: (i) global and local super-venience, which differ in what they take to be the supervenience base, and (ii) weak andstrong supervenience, which differ in their interpretation of necessity. Global superve-nience takes as the supervenience base the world at large. It states that two worlds whichare physically indistinguishable must be mentally indistinguishable. Local supervenience

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takes individuals as the supervenience base. There is discussion in the literature as towhether this base should be confined to the intrinsic physical, chemical, and/or biologicalproperties of the individual, or whether it should also contain external properties, such asits causal or evolutionary history. Local supervenience comes in two varieties. Strongsupervenience states that if two individuals are physically indistinguishable in any possi-ble world, they have to be mentally indistinguishable. Weak supervenience states that iftwo individuals are physically indiscernible in a particular world, they have to have thesame mental properties in that world. So while strong supervenience is a notion thatoperates across possible worlds, weak supervenience applies to intra-world ontologicaldependencies.

3.1. Underdetermination

Given the standard account of supervenience outlined above, can the notion of super-venience be used to say something illuminating about the relation between artefacts andtheir material base? Of the two criteria of adequacy mentioned above we start with theunderdetermination criterion UD. It specifies that any ontological theory of artefactsshould allow for and illuminate a twofold underdetermination of artefacts: A given func-tion of an artefact can be physically realized in many ways (top-down), whereas a givenphysical structure can perform many functions (bottom-up). Can the notion of superve-nience take this into account?

Obviously, top-down underdetermination is part of the idea of supervenience. As wehave seen, the concept explicitly allows for the multiple realizability of mental properties,but there is a serious problem with bottom-up underdetermination. The idea of superve-nience is that two individuals which are physically alike are necessarily alike in their super-vening properties (functional, mental). Here there is no room for underdetermination, andthis applies to both weak and strong supervenience. These notions only differ in theiraccount of necessity, where the first incorporates an intra-world necessity and the secondan across-world necessity. Both types of necessity exclude the possibility that two mole-cule-for-molecule identical individuals in a particular world can have different functions.This, however, is something an ontological theory of artefacts should be able to accountfor.

One way to try to remedy this situation is to enlarge the supervenience base, a moveoften made in the philosophy of mind. The idea would be then to consider artefacts notin isolation but together with their context of design and use. Relative to one contextan artefact can be said to have function F1, whereas the same artefact can have functionF2 relative to another context. The supervenience relation would then spell out the rela-tion between an artefact’s base broadly conceived and one of its functions. The problemwith this move, however, is that we cannot define this supervenience base without referringto the artefact’s function (F1 or F2). This makes the analysis circular. Supervenience is arelation of bottom-up determination, where the higher-order property of function or usecannot be used to specify what the supervenience base should be.3

Another problem we encounter is that artefacts have certain relational propertiesessentially and that many of these relational properties are of a mental kind. An artefact

3 This is obviously part of a larger discussion in the philosophy of mind, which we cannot address here.

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is also an artefact because we have certain mental attitudes towards it. Being an artefactmeans, among other things, being designed, produced, used and regarded as an artefactby intentional agents. The supervenience base should therefore include physical andmental properties. This idea, however, goes very much against the idea of supervenience.The notion was introduced to give an account of how higher-level properties canemerge, while at the same time being determined by, but not being reducible to, thelower-level properties.

A radical solution to many of these problems seems to be to embrace global superve-nience, being the idea that two physically identical worlds are necessarily mentally andfunctionally identical. The supervenience base is enlarged then to include the world as awhole. On this base all the functions of an artefact supervene (F1 + F2). This type ofsupervenience is certainly true of artefacts. It states a commitment to materialism: func-tions of technical artefacts have a material basis. The solution, however, comes with anunwanted price: it ceases to provide much in the way of illumination with respect to arte-facts. It is trivially true but does not create insights in the specific ontological relationshipsbetween an artefact’s physical structure and its functions.

3.2. Realizability constraints

As we have seen, strong and weak supervenience are hard to reconcile with UD, whileglobal supervenience is only trivially true. There are also serious problems with respect tothe Realizability Constraints (RC), which have to do with the specific type of dependencerelation that supervenience incorporates. The dependence is one-way and bottom-up. Iftwo individuals are physically alike, they have to be alike in their supervening properties,whether mental or functional. In the case of artefacts, however, there is also a top-downdependency in the following sense. If an artefact has a certain function, it needs to have astructure that enables this function. In the case of malfunctioning, for example, we canstate what the artefact in a physical or structural sense is supposed to do. In such a caseit is possible to reason from a function to a physical structure. This is incompatible withthe received notion of supervenience. Supervenience does allow for multiply realizablefunctions, but the relation of determination between the physical and the mental is onlybottom-up.

There is another important reason why the notion of supervenience is not rich enoughto account for the complex relation between the function and structure of an artefact. Thishas to do with the formal nature of the supervenience relation. As Kim observes, the super-venience thesis is a thesis about property co-variation and does not give an explanatoryaccount of the relationship between the mental and the physical (Kim, 1994, p. 582). Assuch it is not a theory of the mind–body relation on a par with other theories of mind.Thus it does not say anything illuminating about the nature of the psychophysical depen-dence, it only states a minimal commitment to physicalism in terms of property variation.

In the case of artefacts, the twofold underdetermination of the properties of an artefactat the physical and functional level does not imply that there is an arbitrary relationbetween these levels. Engineering is not based on anything goes. You cannot make a ham-mer from foam, nor can you use foam as a hammer. There are specific dependency rela-tions between these two levels, based on which functional reasoning is possible in the firstplace. You can then reason from the function of an artefact, for example the function of atelephone line to connect two telephones, to a certain physical structure realizing that

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function (copper wire for example). Supervenience, being a formal relation, does notexplain nor illuminate these mutual dependencies.

To conclude, the notions of strong and weak supervenience are not very useful forunderstanding the relationship between the physical properties of an artefact and its func-tional/intentional properties. They cannot account for the twofold underdeterminationbetween an artefact’s function and its structure, nor can they fulfil the realizability con-straints. Global supervenience is too trivial as an ontological theory of artefacts.

4. Artefacts as constituted objects

Lynne Rudder Baker (e.g., 2000) has proposed a general metaphysical theory as analternative to supervenience accounts. This constitution view is intended to describethe relation between, among other things, art works and the materials they are madeof, persons and their bodies, and a river and the water molecules in it. Hence, this viewaddresses the problem that concerns us in this paper. Moreover, Baker (2004) hasapplied her view to the realm of artefacts. Although it is just one possible way of devel-oping a constitution view of artefacts, we take it as our starting point in this paper. Wefirst summarise Baker’s metaphysics of artefacts and then go on to test it with respect toour criteria.

4.1. A possible constitution view of artefacts

According to Baker, constitution is the glue of the material world. The concept is meantto describe virtually all metaphysical relations between middle-sized or everyday objectsand material aggregates; the constitution view is not lacking in ambition. But despitethe name of the project, the notion of constitution is not doing all the work: the constitu-tion view consists of several related concepts, including ‘primary kind’, ‘essential/deriva-tive property’ and ‘circumstances’. We briefly describe each concept before examining aconstitution view of artefacts.

Constitution is conceived as a relation between things of fundamentally different kinds;it is not a watered-down identity relation. Reality must be fragmented before it can beglued together. Baker’s way of doing this is by determining an object’s ‘primary kind’:‘Every object has its primary kind essentially, and entities of different primary kinds havedifferent persistence conditions. Constitution is a relation between things of different pri-mary kinds’ (2004, p. 100). Hence, the key to determining an object’s primary kind, that is,its fundamental ontological type, is to study its persistence conditions. These need not beformulated in structural or geometrical terms: Baker allows and even recommends theidentification of objects in terms of their causal capacities and functions. Constitution ismeant to relate things with different causal powers; if it did not, those who think that enti-ties are told apart by their causal capacities would conclude that constitution is, after all,an identity relation. The causal powers ascribed to constituted objects should, by the way,be conceived rather broadly: Baker, for instance, repeatedly uses the capacity of a flag tomake a veteran cry as an example.

Besides the notion of ‘primary kind’, the constitution view employs the notion of ‘cir-cumstances’: a thing of a given primary kind, for example, an aggregate of water moleculesdoes not constitute another thing of another primary kind, for example, a river, per se, butonly in certain circumstances.

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A final ingredient, that is the least important for our present purposes, is the distinctionbetween two ways of having properties, namely ‘essentially’ or ‘derivatively’. Intuitively,some properties are possessed by both the higher-order object and its material basis: if,for instance, the mechanism in an ordinary clock produces a loud ticking noise, the clockdoes. In the constitution view, the mechanism has this property essentially; it could notcease to make the noise without ceasing to be the mechanism that it is. The clock has thisproperty only derivatively; repairing it might stop it ticking without ending its existence.Note that, again, we employ the intuitive persistence conditions of objects to settle thisissue.

Summing up, the constitution view describes the relation between an object and itsmaterial basis. The relata are conceived as entities of different primary kinds with the sameset of properties, either essential or derivative. The constitution relation that glues theseentities together is non-reflexive, since it only holds between things of different primarykinds; asymmetrical, as the application to artefacts will make clear; and it holds in certaincircumstances and creates new, essential causal powers in the constituted objects.

Let us see how this view applies to artefacts, following in Baker’s own (2004) footsteps.4

This may not be the only way to apply the constitution view; indeed, we briefly consider analternative at the end of this section.

Baker characterises the material basis of an artefact as an aggregate, meaning that itsidentity conditions are exhausted by the identity conditions for its parts and that its pri-mary kind is a hybrid or, more accurately, a list of the various primary kinds of its parts.The material basis of a hammer, for instance, is an aggregate of wood and steel that wouldbe different if either part was damaged or replaced and that cannot be described morecompactly than in terms of wood and steel. The artefact itself, however, has a differentand more unitary primary kind, namely its (proper) function,5 ‘determined by the inten-tions of its designer and/or producer’ (ibid., p. 102). Summarising Baker’s own formula-tion, an object x is an artefact if and only if: (Art. 1) it has one or more designers6 d whoseintentions in part determine its proper function and on whose intentions the existence of xdepends; (Art. 2) x is constituted by an appropriate aggregate, selected or arranged by d torealise x’s proper function. Framed in terms of the dual nature thesis, (Art. 1) expresses theintentional nature of an artefact and (Art. 2) its physical nature.

This analysis of the nature of the artefact x is supplemented with two conditions on theaggregate a that constitutes x and with a characterisation of the circumstances in which a

constitutes x. An aggregate a is appropriate if and only if: (Agg. 1) a contains enoughitems of suitable structure to enable the proper function of x to be performed and(Agg. 2) the items in a are available for assembly in a way suitable for enabling the properfunction of x to be performed. The circumstances in which a constitutes x cannot be spec-ified precisely and exhaustively, but comprise, among other things, that a is in the presenceof knowledgeable persons d who deliberately and successfully set out to create x by manip-ulating a.

4 The remainder of this subsection is a brief summary of Baker (2004), Sect. 2. All subsequent references are tothis paper.5 Hence, in the case of artefacts, persistence conditions are not taken as a guide to primary kind property.6 Presumably, ‘designing’ must be taken in its usual sense of ‘product designing’, that is, constructing (a

blueprint for) an object. This implicit focus on product designing will be shown to conceal a deeper problem withthe present application of the constitution view to artefacts.

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The central definition of the constitution view of artefacts reads: a constitutes x at time tif and only if a and x are spatially coincident at t in x-favourable circumstances. To theconditions on aggregate a, artefact x and x-favourable circumstances listed above, Baker(ibid., p. 104) adds two modal conditions that underline the importance of the circum-stances and that introduce an asymmetry between a and x: any different aggregate in x-favourable circumstances necessarily constitutes an artefact of the same functional typeas x, for example, a larger hammer; and a may not constitute a hammer, namely in ham-mer-unfavourable circumstances, for example, when found on a hitherto unexploredasteroid.

4.2. Functional essentialism and ontological stacking

Before turning to our criteria, we raise an internal problem concerning the constitutionview of artefacts. It may be regarded as an advantage of the constitution view that itallows for the existence of non-identical but spatially coincident entities. However, inthe case of artefacts this liberality leads to what we call ‘ontological stacking’, that is,the existence of multiple spatially coincident artefacts.

On the constitution view described above, the proper function of an artefact determinesits primary kind. An aggregate constitutes an artefact that has a proper function as its pri-mary kind property, if the aggregate is in certain circumstances that involve the deliberatedesign of an artefact by means of the aggregate. Hence, in many cases of redesigning arte-facts, the original object ceases to be an artefact of one kind and becomes one of anotherkind. An example would be redesigning a rubber tyre by suitably connecting it to a rope,through which it, presumably the constitutive aggregate, enters a new life as a swing.Alternatively, an artefact may cease to be an artefact altogether, although some aggregatepersists, as when a car changes into a twisted mass of materials after being crushed in arecycling unit.

This essentialism on proper functions is intuitively attractive and virtually undisputedamong philosophers. Unfortunately, it leads to a variety of problems (Houkes & Vermaas,2004), one of which is pertinent to the constitution view. Some artefacts, such as cellphones, are multifunctional; others acquire new proper functions without losing the oldone. Take, for instance, Aspirin, a popular drug used to alleviate pain and to reduce fever.Aspirin has, in recent years, attracted attention because of other beneficial properties, suchas preventing blood clots and perhaps some forms of cancer. Indeed, it is now prescribedto cardiovascular patients as a preventive drug. This use of Aspirin has changed accord-ingly: cardiovascular patients now take tablets regularly and at a lower dosage than thosewho take Aspirin to get rid of a headache. In terms of functions, this case is naturallydescribed as Aspirin acquiring a new proper function, which co-exists peacefully withits old one. Aspirin tablets as a type can thus be used as painkillers or cardiovasculardrugs. Token tablets usually have one function or the other, although it is conceivable thata cardiovascular patient takes his daily dosage while having a headache, thus deliberatelygetting rid of two problems at once.

To see how this creates a problem with the constitution view, suppose that someonebuys a box of Aspirin as a prescription drug. Then it seems that a tablet in this box con-stitutes a (spatially coincident) blood thinner. Now suppose that a dinner guest complainsabout a headache, and is given a tablet from the package; say, the first one. Then it seemsthat this tablet constitutes a spatially coincident painkiller (that is, an artefact with the

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proper function of alleviating a headache). What happened to the blood thinner? Did itcease to exist during the process of being served as a painkiller? If so, at what point?Or did the tablet acquire a new proper function at some time during this process, consti-tuting both a painkiller and a blood thinner? Do all tablets in the container now constitutetwo artefacts? There is something distinctly unattractive in this type of ontological stack-ing, in which two distinct functional objects are spatially coincident with each other andwith an aggregate that constitutes both; for one thing, the relation between the two arte-facts remains unclear, although the claim that, here, the blood thinner is a painkiller doesnot raise any eyebrows; or at least not those that belong to philosophers.7 Nor is there, inthis context, anything sacred about the number three; multifunctional material objectsmay constitute many, perhaps indefinitely many distinct artefacts, all of which have a dif-ferent functional essence.

This problem may not lie with the constitution view as such, but mainly with the com-mon tendency to identify proper functions as the essence of artefacts and to interpret‘designing’ exclusively as ‘product designing’, that is, as constructing an object or its blue-print. Elsewhere, it has been suggested to take the plans in which artefacts are embeddedas their essential characteristic and to broaden the notion of designing to, primarily, con-structing and communicating a way of using an object, which may exist previous to design-ing (Houkes & Vermaas, 2004). Then, the Aspirin tablet might be said to become apainkiller rather than a blood thinner as soon as the host takes it from its box for thatpurpose, and the painkilling use plan starts to be executed. It remains to be seen whetherthis way of determining the primary kind of artefacts can be consistently developed, but itseems to avoid ontological stacking.

4.3. The deficiencies of the constitution view

Let us turn to testing the constitution view of artefacts against the two criteria presentedin Section 2, which quickly leads us back to the internal problems with determining pri-mary kind properties.

At first glance, underdetermination seems relatively unproblematic. Roughly speaking,the structure-to-function side of (UD) can be accounted for by referring to different sets ofcircumstances and the function-to-structure side by identifying ranges of suitable aggre-gates. In different circumstances, an anvil can be a doorstop, just as a suitable anvil canbe made of different alloys in different shapes.

Taking a closer look, some problems surface. For instance, given the designer-orienteddevelopment of the constitution view presented in Section 4.1, the question arises whetherthere is sufficient ‘conceptual freedom’ to account for structure-to-function underdeter-mination. It is beyond doubt that an anvil has the causal capacities to play the role of adoorstop, but it is equally clear that it has not been designed to do so, at least not inthe usual sense of ‘designed’. From here, two routes may be taken. A hardliner could insistthat using an anvil as a doorstop does not mean that the metal aggregate constitutes a

7 Stratification does not resolve this issue. Suppose one claims that, in the Aspirin example, the blood thinnerhanded to the ailing guest constitutes a painkiller and is itself constituted by a tablet containing acetyl salicylicacid. However neat, this ontological organisation leads to counterintuitive results. The relation of constitution is,according to Baker, not transitive (2000, p. 45). In the current example, the tablet would then constitute a bloodthinner, and the blood thinner a painkiller, but the tablet would not constitute a painkiller.

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doorstop: we have failed to give an example of structure-to-function underdetermination.This leads to problems, however. For the only remaining examples of this type of under-determination appear to be multifunctional items, such as Aspirin tablets. These, weargued earlier, lead to ontological stacking. A libertarian might concede that the metalaggregate constitutes a doorstop in some circumstances, namely those in which it has beendeliberately and rationally used as such and this way of using an anvil has been commu-nicated to other agents. This liberal notion of ‘plan designing’ replaces the intuitive notionof ‘product designing’ employed in the constitution view of Section 4.1. Besides saving thephenomenology, it avoids ontological stacking in the way sketched at the end of Section4.2. It does, however, render an artefact’s primary kind property somewhat inscrutable.Instead of identifying it as an artefact’s proper function, it becomes the use plan in whichthe artefact is embedded. If this is a respectable property at all, it is highly relational andtransient.

However, these problems with accounting for (UD) are small in comparison with thoseraised by (RC). This states that the ontology of artefacts should constrain realizability,and so enable us to understand the possibility of deriving conclusions about the materialbasis from claims about an artefact and its function, and vice versa; and that the ontologyshould provide insight into the interaction of the material basis and the artefact, forinstance in standard engineering practices for designing maintenance and repair proce-dures and for finding causes of failure.

The constitution view of artefacts straightforwardly supports one type of inference,which takes descriptions of the material basis and relevant circumstances as premisesand concludes that there is an artefact that has a certain proper function. This inferencedirectly reflects one of the modal conditions on the circumstances. Hence, structure-to-function inferences are, ontologically, on solid ground.

The other types of inferences, however, raise serious problems. The function-to-struc-ture type, for example, product designers selecting materials, is trivialized. In the consti-tution view of artefacts, claims about the function of an artefact entail only that thespatially coincident aggregate is ‘appropriate’, meaning that the aggregate contains itemsof ‘suitable’ structure that have been ‘suitably’ assembled. To note just how uninforma-tive this explanation by synonymy is, take the inference from the function of an airplaneto its structure. In the constitution view presented in Section 4.1, there is nothing to sup-port the claim that an airplane is made of aerodynamically shaped, lightweight materi-als. Instead, it only supports the claim that the materials are ‘suitable for flying’ and‘suitably assembled’. This claim leaves us in the dark as to which structural propertiesare responsible, a matter of utmost importance in engineering design. In the practiceof reverse engineering, for instance, engineers painstakingly analyse a product, com-monly manufactured by a rival firm, to find out how it performs its function. A reportthat concludes merely that the aggregate is suitable is not likely to put a smile on theproject leader’s face.

The problem is exacerbated when we turn to statements concerning malfunctioningartefacts. In cases that are not analysed as having been caused by ‘human failure’, the veryfact that these artefacts are malfunctioning shows that the aggregate that constitutes themis not suitable for performing the artefact’s function. Planes crash and pens run out of ink.Introducing Franssen’s (2006) helpful distinction, artefacts can malfunction on either thetoken or the type level. The constitution view faces problems at the token level, butespecially at the type level. Suppose that a type of airplane, say Howard Hughes’s Spruce

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Goose,8 fails to fly. How does the constitution view account for the relation between theartefact and its constitutive aggregate? Simply claiming that a suitable aggregate consti-tutes the artefact is unattractive, but the only alternative is to say that the unsuitableaggregate did not constitute an artefact at all, which flies in the face of claims by engineersand potential users.

It seems more plausible to modify the constitution view as follows: although the design-ers believed that the aggregate was composed of suitable materials and that it was arrangedin a suitable manner, this might not actually be the case, or, for token malfunctioningitems, this is no longer the case. Hence, the conditions that determine whether an aggre-gate is appropriate or not refer to the beliefs of intentional agents, either designers or usersand not to de facto properties of the aggregate in question. The original constitution viewpresented in Baker (2000) offers this possibility, whereas the application to artefacts pre-sented in Baker (2004) does not. The original view, however, has the disadvantage that therelation between the higher-order object and its material basis depends largely, or evenexclusively, on the circumstances: there are no conditions of appropriateness on the aggre-gate. In this way, malfunctioning can be accounted for, but function-to-structure infer-ences would be left without ontological support.

It is, indeed, an open question how the necessary amendments to the constitutionview should be made. One may impose additional conditions on (designer’s beliefsabout) the aggregate. Alternatively, one may take a closer look at the circumstancesunder which a physical structure constitutes an artefact. Baker characterised these interms of deliberate design; to put it shortly, the circumstances referred to a large setof intentions and intentional actions. To solve the malfunctioning problem, they shouldalso include beliefs about physical properties of the structure at hand. Since the circum-stances mentioned by Baker also refer to intentional agents, the circumstances are amore natural place to make amendments than the aggregate itself. Now it seems thatthe pendulum is set for a backwards swing: what supports these beliefs about the aggre-gate, if it is not properties of the aggregate itself? In terms of our dual nature thesis, theproposed solution might exaggerate the intentional nature of artefacts at the cost of theirmaterial nature.

5. Conclusion: the hard problem

In the previous two sections, we have argued that neither supervenience accounts nor theconstitution view provide an ontology of artefacts that is adequate for our two criteria (UD)and (RC). Supervenience accounts either conflicted with these criteria or satisfied them atthe price of triviality; the constitution view was found to falter on (RC) in particular.

It might seem that the problems pointed out in this paper are easily remedied, and thatthey reflect the relative disinterest in artefacts rather than a deep philosophical problem.After all, we have indicated ways of modifying the constitution view in such a way thatit applies successfully to artefacts; a similar effort might be made for supervenienceaccounts or other general metaphysical views, which we have not discussed here. However,we think that there is a hard problem that underlies the more specific criticisms that welevelled at the two frameworks examined in this paper.

8 This airplane was the only token of its type, and was never seen to gain an altitude over fifty feet.

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To see where this problem lies, let us return to the thesis that sparked our interest in theontology of artefacts and that inspired our criteria: the thesis that artefacts have a dualnature. Taken literally, this thesis is easily formulated in terms of either supervenienceor constitution. In both cases, a higher-order object or property is characterised function-ally and thus intrinsically connected to the intentional realm and a material object, char-acterised in physical terms, is said to underlie or coincide with it. As noted in Section 2,our criteria do not concern the dual nature of technical artefacts as such; rather, theyaddress the flexibility and rigidity of the relation between these natures.

The hard problem in the ontology of artefacts is to strike a balance between these twoaspects. Although supervenience accounts adequately reproduce the flexibility of the dualnature relation if a sufficiently broad (i.e., global) material basis is chosen, this very factundermines their possibility to account for function-to-structure inferences and thus tosatisfy (RC). A similar problem was shown to arise for the constitution view. Hence,emphasising structure-to-function underdetermination seems to go hand in hand with alack of support for function-to-structure inferences, and vice versa. This dilemma maysound suspiciously familiar to some readers; indeed, it may be akin to the mind–bodyproblem that has plagued philosophy for centuries, and that partly motivated the meta-physical accounts examined in this paper. However, it might be even more pressing inthe case of artefacts, because both the flexibility and rigidity of the dual nature relationare so salient in the practice of designing and using artefacts. This salience also frustratesthe response that (UD) and (RC) are incompatible, that is, that they cannot be satisfied bythe same account. If this is indeed the case, it seems that they must be discarded together,as two sides of the same coin. However, since it is hard to conceive of criteria that enjoymore phenomenological support, an ontology of artefacts would then be on shaky groundindeed; selecting alternative criteria may be even harder than satisfying the ones givenhere.

For the moment, discarding the criteria when faced with the present difficulties seemslike avoiding the details of a specific domain to save a general metaphysical account.Although generality is a great virtue, it may be overpriced in contemporary metaphysics.Our criticisms suggest that the hard problem in the domain of artefacts calls for sophisti-cated conceptual engineering. Artefacts need a tailor-made ontology; philosophers haveleft them in the cold for too long.

Acknowledgements

The research for this paper formed part of the program The Dual Nature of TechnicalArtefacts, supported by the Netherlands Organisation of Scientific Research (NWO). Wewould like to thank Peter Kroes for comments on an earlier version of this paper.

References

Baker, L. R. (2000). Persons and bodies. Cambridge: Cambridge University Press.Baker, L. R. (2004). The ontology of artefacts. Philosophical Explorations, 7, 99–111.Franssen, M. (2006). The normativity of artefacts. Studies in History and Philosophy of Science, 37, this issue.

DOI:10.1016/j.shpsa.2005.12.006.Gillett, C. (2002). The dimensions of realization: A critique of the Standard view. Analysis, 62, 316–323.Houkes, W. (2006). Knowledge of artefact functions. Studies in History and Philosophy of Science, 37, this issue.

DOI:10.1016/j.shpsa.2005.12.011.

W. Houkes, A. Meijers / Stud. Hist. Phil. Sci. 37 (2006) 118–131 131

Houkes, W., & Vermaas, P. E. (2004). Actions versus functions: A plea for an alternative metaphysics ofartefacts. The Monist, 78, 52–71.

Kim, J. (1994). Supervenience in philosophy of mind. In S. Guttenplan (Ed.), A companion to the philosophy of

mind (pp. 575–583). Oxford: Blackwell.Kroes, P. (2006). Coherence of structural and functional descriptions of technical artifacts. Studies in History and

Philosophy of Science, 37, this issue. DOI:10.1016/j.shpsa.2005.12.015.Kroes, P., & Meijers, A. (2006). Introduction: The dual nature of technical artefacts. Studies in History and

Philosophy of Science, 37, this issue. DOI:10.1016/j.shpsa.2005.12.001.Van Inwagen, P. (1990). Material beings. Ithaca, NY: Cornell University Press.Wiggins, D. (2001). Sameness and substance renewed. Cambridge: Cambridge University Press.