1. Wittgenstein's Hinges Elaborated

Our proposal draws on a development of Wittgenstein's ‘hinge’ concept, as interpreted and developed in recent studies of his later writings, in particular On Certainty.Footnote ³ In trying to understand a scientific or legal or theological discourse and those of many other genres, from a philosophical point of view, that is with respect to the concepts in use, we look for propositions which have gone unformulated and so unchallenged and once formulated seem germane to the assessment of the intelligibility of habitual procedures and practices in a certain field. We try out hinge-pairs that might shape our importation of content into the bare bones of a formal presentation of an explanation, a practical manual or relevant cluster of discipline defining propositions. The modality we are hoping to establish clearly, via Wittgenstein's ‘hinge philosophy’, occupies the territory of the synthetic a priori, at a local level, in respect of technically advanced domains of enquiry.

Danielle Moyal-SharrockFootnote ⁴ and others have interpreted hinges not as ‘somethings’ that underlie or support or imply practices or procedures. Hinges are implicit in our activities, but they do not have an independent existence. We know them only as expressed in a proposition-procedure pair, doppelgängers of one another as Moyal-Sharrock has it. Once made explicit, propositions like ‘Life on earth has existed for millions of years’ can be examined and sometimes tested as putative matters of fact. If they seem plausible they can be used to defend the point of procedures and practices such as going to Lyme Regis and cracking rocks in the hunt for fossils.

In general, a propositional expression of a hinge seems to express something entirely obvious but nevertheless a matter of fact which might have been otherwise. Its doppelgänger is taken to be a fertile and trustworthy procedure that makes sense in the light of the truth or plausibility of its propositional partner. In playing golf on earth the propositions and procedures requiring attention to the gravitational field is a hinge cluster, the presence or strength of which is never discussed on the golf course – but this is not the situation for golf on the moon. Alan Shepherd had to attend to the attributes of the lunar gravitational field, attributes of the earth's gravity that had been taken for granted in the corresponding proposition-practice doppelgänger pair on earth. The planning and interpretation of experiments on the space station are framed by different hinge proposition – hinge procedure pairs from those on earth.

Hinges exist only as expressed in taken for granted pairs; hinge propositions and their doppelgängers, hinge procedures or practices. The relevant propositions are unformulated and so not examined empirically, and the paired procedures are habitual and more or less skillful, usually not guided by an actor paying attention to explicit rules.

Authors of established genres of scientific discourses and other professional literary genres work with practical modalities, natural necessity and empirical possibility. These modalities are established within a framework of tacit knowledge and skill, we can set out as Wittgensteinian hinges – expressed as doppelgänger pairs, propositions and practices. A propositional hinge serves as the a priori condition for the intelligibility of the discourse in question (‘There is a layer of more ancient writing under the visible text’). A practical hinge, its doppelgänger, is expressed in the mastery of the skill which should be used to achieve a certain result. (‘Here is a photographic technique to make the ancient writing legible’).Footnote ⁵ Palaeography and mass spectroscopy, musicology and economics we see as intelligible in similar ways. Each has its implicit, taken for granted basis, in the proposition – procedure hinges of a sophisticated practice, the hinges on which the intelligibility of a professional discourse and its associated practices turn.

2. Affordances Amplified

Our second methodological concept is ‘affordance’, borrowed from a coinage by J. J. Gibson.Footnote ⁶ He used it as a term for referring to certain perceptual phenomenon. It was a radical departure from the sense data theories of such as Russell and the constructionism of such as Kant. In those theories what we see is said to be the product of a cognitive process by which elementary sensations, such as coloured patches in the visual field, are synthetized into objects and processes. Gibson argued that certain invariant structural properties of the energy flux within which a person was embedded afforded perceptions of material things to people and animals as they explored the flux of electromagnetic and sonic energy within which they lived. Gibson pointed out that we do not perceive a thing in general, but as an instrument for action. Most people who see a strip of metal as a knife, see it as a cutting instrument. In this terminology, we say a knife affords cutting. But only in a human context does a certain piece of steel have that attribute. We can also say that a floor affords walking to people, while a lake does not, though it was said to have for Jesus.

According to an affordance analysis of natural science we find out about the dispositions of material set-ups, including the products of experimental procedures in concrete situations. The usefulness of the experimental method in science depends on thinking and acting within a certain kind of reality; material substances embedded in a complex cluster of material and other conditions, including the availability of samples of elements such as the halogens, appropriate glass ware, and skilful chemists. ‘What is the boiling point of liquid bromine at NTP?’ This is a question that can be answered only when the answer it is treated as an affordance of a complex ‘entity’ including a sample of liquid bromine, a heat source, an experimental apparatus, an earth-like atmosphere, a gravitational field, and a skilled experimenter.

Taking chemistry to be a science of procedures, the products of chemical research are primarily the means for changing the dispositions of material substances as displayed in what they afford in response to the activities of certain agents. Their observable or occurrent properties are just ephemera – the reality is dispositional. Moreover, a skilled experimenter is needed to make all this happen. David GoodingsFootnote ⁷ followed the steps by which a phenomenon that depended on the skills of Michael Faraday was transformed step by step to a phenomenon that anyone could reproduce. The chemistry of the action of dioxygen on iron is brought about in a laboratory by a chemist, while the old sheet of iron rusts in the back fence without human intervention. The other dimension of chemistry – its atoms and molecules, requires additional mereological concepts we have yet to introduce.

An affordance is relative to context, in particular to the settings of specific interactions between sentient beings and the material world. Throughout this paper we will use the word ‘complex’ for the total entity the affordances of which are explored in a research program. It is the whole complex that has affordances. Ice affords walking to a wolf, but not to the elk it is pursuing. Affordances are contextually sensitive dispositional attributes of complexes that include agents, so that ‘wolf-walking’ is an affordance of a local ‘wolf-ice’ system, but not of an ‘elk-ice’ system; the weather, there are no such systems in mid-summer in the Yukon; and as much more detail as will make the story plausible. What the system affords a wolf as an action program there is no such a program available to an elk.

Recently the concept of ‘affordance’ has been elaborated to distinguish between the actions that are possible in a given complex to an agent of a certain kind, and the products of the actions of such an agent. Thus, a knife affords cutting to a carver, and the carver's activities afford slices of meat to a diner. In applying the concept in the philosophy of natural science such as genetics, affordance as a possible action and affordance as a possible product of an action is a pair of closely related and useful analytical concepts. We will call the complex acted upon the ‘target complex’.

From the point of view of the grammar of a chemical or a physical discourse an affordance is a disposition or capacity as ascribed to a certain material being to display an attribute say, ‘liquidity’, or yield an entity, say ‘chlorine gas’, each understood as the product of chemical reactions or physical manipulations, that is when certain substances are arranged or acted upon in a certain way by a human agent. Written out in full the attribution of an affordance has the form of a conditional – ‘if a certain procedure is carried out on a certain substance by a certain agent it will display a certain attribute as the manifestation in the context of a certain disposition or yield a certain substance as the realisation in a certain context of a certain disposition.’ Adding carbon to iron increases the tensile strength of a rod, that is a dispositional property it displays only when put into tension in some machine or stressed in some other way. Adding zinc to a solution of hydrochloric acid completes a system that yields a gas. In turn, we label the product ‘hydrogen’ on the basis of a manifestation of certain dispositions that are not dispositions of the target system. A salt pan in sunny weather affords crystalline salt, which was not a component of the salt water.Footnote ⁸

But why is the notion of a complex so important here in contrast to the hypothetico-deductive analysis of isolated experimental procedures in supposedly tidied up environments? Let us take instances from nanotechnology, materials science, and chemistry in order to highlight this crucial point.

The mode of access to a nanochemical compound, that is to say the way nanochemists and experts in materials science synthesize it, cannot be eliminated from the final product insofar as it contributes to the very determination of the whole body and its correlative parts and structure. The structure of the crystals may also differ if the chemical device of precipitation changes. It can even differ with the same chemical device, depending on the size of the crystals, which itself depends on what surrounds the body in the process of individuation. The internal arrangement can be grain-size sensitive. Chemical operations and the other chemical bodies which surround the substance at stake during the ongoing synthesis do not ‘reveal’ pre-existing chemicals but, on the contrary, actively take part in their very constitution. Conversely, the substance takes part in the redefinition and the chemical reactivity of what surrounds it. The scrutiny of nanochemical practices is relative to the constitutive role of the surroundings and the mode of intervention on the substance being synthesized. Any definition is always open and provisional, of these ‘active’ chemical bodies.Footnote ⁹ What a particular substance contains, and the internal structure of a molecule or a material, can change depending on the solvent and the ‘whole context’, as it has been known for a long time by chemists in the case, for instance, of acid or oxidative properties.

It is impossible to abstract the substance from the operative framework in which it is stored or used. This requirement is particularly important in analytical chemistry and biochemistry. Accordingly, the practice of inserting a ceteris paribus clause cannot deal with any particular reaction of the same chemical in all circumstances but is, by contrast, primarily concerned with what we shall call the couple {chemicals-surroundings}. The surroundings can be, among many other possibilities, a solvent or a mixture of solvents, a gas vector, a mineral matrix, i.e., the substrate in which the molecules to be characterized and titrated are located (e.g. biological fluid, vegetable matter, etc.). Only one parameter must vary in order to characterize the chemical behavior of this couple in relation to the qualification ‘all things being equal’. In this respect, the use of the clause does not permit any nomological implication in connection with the intrinsic properties of bodies. The conclusion of chemical reasoning is about what the couple chemicals-surroundings under study affords to a certain kind of agent.

We have now to include the instrumentation that enables chemists to quantify their products in our investigation. The central problem is that of the co-stabilization of an apparatus with the set of bodies with which it interacts, which includes various acts of modelling as part of the global project. It is the whole complex composed of the apparatus, the methods carried out for calibrating and using it, the chemicals and the surroundings at that moment and that place, and the ancillary conditions, which should be the starting point of our epistemological enquiry.Footnote ¹⁰ To investigate the meaning of the ceteris paribus clause in chemistry requires an investigation of the conclusions that chemists can relevantly draw from comparisons with reference to what the complex {apparatus-methods-chemicals-surroundings-devices-agent} affords.

In this context of activity, a method can never be blandly detached from the content it yields. The association between the apparatus and the method depends on the surroundings, the device, the skills of the experimenter and the chemicals under study. The six elements of the complex are co-adapted to one another. If chemists change a factor, for example a type of column, the mode of injection of the solvents, the quantity of product, the matrix from which it originated, the preparation of the sample, the detector, among other possibilities, they will have to resume the process of co-adaptation from the very beginning because the complex does not work in that way anymore. In short, chemists must stabilize a specific domain of application of the whole complex to determine a quantity of a particular type of body within certain limits imposed by standards of normalization and laws. The sentence ‘all things being equal’ encompasses the co-adaptation and the channeling of multifarious fluctuations which, in turn, leads to the very possibility of making holistic inferences as regards the performance of the whole complex within the normative framework of a quality control procedure. Consistency and inconsistency are about different measures or inferences taken or drawn from what the whole complex affords. A result or an inference must fit into the complex; and the performance of the complex is more or less justified depending on how well it hangs together as a whole for achieving its particular goal. The density of such interconnections contributes to the consistency of the empirical outcomes, and to that of the inferences, obtained or made from the complex as to the question at stake.Footnote ¹¹

This line of analysis, we propose, is germane to the philosophical understanding of any professional activity which involves principles and practices. For example, French cooks, following traditional recipes unreflectingly, never realised, it seems, that there was a hinge conflict until Brillat-Savarin made clear the hinges on which European food turned. On the one hand was the Burgundian cuisine according to which salt and sweet dishes must be strictly separated. On the other there was the Gothic cuisine in which every dish involved a mixing of salt and sweet items. Brillat-Savarin tried to show that the propositional hinge of the Gothic cuisine was empirically false by drawing on what has turned out to be a spurious ‘physiologie’.Footnote ¹²

In like vein we would analyse philosophical debates about the death penalty by digging out the hinge pairs, propositions and practices, to bring to light contingency where unexamined assumptions of necessity of some sort had previously reigned. For example, we might reflect on the status of the propositions ‘Executing murders must reduce the murder rate’, ‘The death penalty is a deterrent’, and so on in different discourse genres. For some people it seems obvious that it must be so. For others these propositions are as clearly mistaken. According to the ‘hinge philosophy’, if one wishes to the change the practices one must also change their propositional doppelgängers.

In life we are eliciting affordances, that is what it is possible for an actor of a certain kind and particular abilities in certain circumstances to do, and what products it is possible for such an actor to elicit.

3. From Dispositions to Causal Powers

Considering natural or artificial complexes in terms of their affordances invites the use of dispositional attributions in describing their potentialities, propensities and capacities. If treated in a certain way a certain complex can afford such and such a phenomenon to an informed investigator under certain conditions. In a research project, be it ever so humble, such as a person or persons trying to ascertain what are the possible affordances of a pail of fresh milk under certain condition and at the hands of a farmer. These will include some occurrent phenomena and some dispositions as permanent possibilities. It is quite another matter to declare that in describing the conditions under which an affordance is elicited as a cause and that affordance itself as an effect of what a complex affords. Ryle's famous analysis of the meanings of propositions in dispositional ‘if – then –’ form as inference licences is germane to the topic. In a conditional statement the antecedent clause refers to an occurrence and the consequent clause to another occurrence. Ryle's point was that merely embedding the descriptions of two successive phenomena in an ‘if – then –’ frame adds no further empirical content to a simple conjunction of the two descriptions.

There is a further consequence of Ryle's analysis of the meaning of dispositional concepts. To be intelligent is to be disposed to solve problems quickly and correctly, that is if presented with a problem then an intelligent person solves it quickly and correctly. We look in vain for an attribute that is the person's intelligence. This follows directly from his ‘inference licence’ treatment of dispositional statements in ‘if – then –’ form.

Nevertheless, in so far as a dispositional attribution is true of a complex when the relevant affordance is not being displayed, it seems reasonable to suppose that there must be some feature of the complex that is permanent and that grounds the continuity of the attribution of the disposition to situations when the complex is inert.

Moreover, the display of an affordance does not just happen. Its appearance on the scene is a consequence of some agent acting on the original complex. A frozen lake only affords walking to an able bodied wolf. This observation leads directly to questions of the possibility of including causal concepts in our methodology, but which causal concepts, Humean or agentive? Two important ‘half way’ proposals for an enriched and more realistic account of causality – Cartwright's ‘nature's capacities’Footnote ¹³ and Popper's ‘propensities’Footnote ¹⁴ have been proposed. Neither is exactly a synonym for ‘causal powers’. Both capacities and propensities are dispositions without agency. To think in terms of affordances necessitates including agents in the story whenever the antecedent state brings about the consequent state expressed in the affordance language. A complex affords the possibility of action to an agent.

Chemical ‘materiality’ is not the sensory stimuli that material stuffs provide, but rather their potential for transformation in a series of chemical experiments and industrial transformations.Footnote ¹⁵ Metals, alkalis, earths and acids disappeared when chemists transformed them into alloys or salts; but they reappeared in subsequent experiments on salts and alloys. Our attention is drawn to the nature of the target of these manipulations. It is a complex as we have described above with several necessary constituents, including the experimenters.

The concept of ‘dispositional property’ and its relation to the concepts of ‘causality’ and ‘causal powers’ has been the subject of detailed study particularly by Stephen MumfordFootnote ¹⁶ as a response to the anti-dispositionalism of D. M. Armstrong.Footnote ¹⁷ The conditional format shapes practical knowledge into operations (procedures) and outcomes (products). To understand how chemicals react against others, chemists need to refer to their selective capacity to interact with one another within a precise context. Products are said to be active in a context of action, and cannot be otherwise in the sense that chemists need active bodies to explain what they are doing. If we act upon a chemical in a specific way in a particular context, then chemists will observe such or such behavior. Knowing that something is a chemical means knowing certain observable effects of certain ways of acting upon it, and ways it can itself exercise causal powers.

This situation cannot but evolve over time. What water is today for chemists does not correspond to what it was in the past.Footnote ¹⁸ Whatever may be the chemical under investigation, new instruments and new empirical conditions enable chemists to stabilize new substances and properties. The definition of a chemical body is thus always provisional and, at least partly, operative. When referring to a chemical substance using everyday language (e.g., ‘carbon dioxide’), or a chemical formula (e.g., CO₂) and its correlative structure, chemists are implicitly referring to a stabilized set of properties. In this respect, a chemical product concisely embodies the knowledge chemists have of the observable effects likely to occur when they produce or act upon this product at a particular time of the history of chemistry. Various relationships may obtain between concrete cases of this format. We note the emphasis on the procedural item in a hinge expression. The same is true of the evolution of a game – certain hinge propositions and practices must be sustained for it to be the same game. Cricket survived the change from curved to straight bats during the nineteenth century. ‘Bats are curved’ was not a hinge proposition for W.G. Grace, nor was it was it for cricketers in the eighteenth century.

We propose that we should treat chemical, social and cultural examples as susceptible of essentially the same style of analysis in search for the shared presuppositions that make them intelligible, each to its own public. These are only completely revealed as proposition-procedure pairs, hinges.

4. Mereological Fallacies

Almost all disciplines deal in parts and wholes. It is not just physics, chemistry and biology which are susceptible to mereological fallacies, but so too are anatomy, neuropsychology, psephology, linguistics, musicology, the law, the theory of war and so on. Recipes list ingredients or constituents rather than atomistic parts, but we will presume that the relation of eggs and flour to a cake is, for our purposes, more or less the same as that of gear wheels to a drive train, or bricks to a wall.

The first mereological fallacy is to ascribe to a part of a complex an attribute the meaning of which is determined by some feature of the whole complex from which that part has come. Bennet & HackerFootnote ¹⁹ have identified the attribution of cognitive attributes whose meaning is determined by whole person criteria to parts of a person, in particular the brain, as just such a mereological fallacy. This argument is not without difficulties, in particular whether a human brain is part of a person or part of the body of a person. Ascribing to a part of a molecule, for instance a group of atoms, a property that the molecule has as a whole (e.g., lipophilicity, basicity or fluorescence) is also committing this kind of fallacy

The second mereological fallacy is to project back into a whole as a constituent or part, something which has been produced by a specific manipulation of that whole in a well-defined context. Dealing with this fallacy requires care because in many cases product to constituent projections are legitimate. A motor mechanic extracting a nut from an engine, takes it for granted that that nut was a part of the engine. It is a hinge on which the manuals and practices of a repair shop turn. On the other hand, a van der Graaf generator produces a spark but the spark was not part of the generator. With the concept of ‘affordance’ in hand we can turn to resolving the question of which projections of product discoveries to the wholes from which they have been extracted as constituents of those wholes are valid.

Affordances as products appear in the everyday world of visible and tangible apparatus, and conform to its substance-property metaphysics and its ‘atomism’. What determines whether a projection of products as constituents of that of which they are products is a fallacy? Electrons emerged as affordances in J.J. Thomson's experiments and were quickly projected back as constituents of the atoms from which they had presumably come. Electrons as entities play a role in almost all pictures of the details of natural processes. References to orbiting spinning electrons are features of nearly every chemical discourse.

When we discover that incandescent sodium affords two yellow spectrum lines by passing the emitted light through a spectrometer what is affording this phenomenon – sodium atom-cores having a certain electronic configuration absorbing and emitting energy. If this makes sense, how have we managed to outflank the second mereological fallacy? We know there are no colours as constituents of atoms, as there are colours as constituents of the surface appearance of the Mona Lisa. In the Bohr model (conception) of an atom it is taken for granted that electrons are constituents of atoms because atoms afford electron phenomena under certain manipulations by thousands of physicists and chemists. Electrons are nothing like spectral colours, why is it taken as unproblematic to assign them to the category of constituents of the inner structures of atoms?

5. Fungibles

An important feature of the natural sciences is the way that at a certain scale the entities that are referenced in the propositions of certain hinges and manipulated in the related procedures change their character. At level n they can be individuated, for example cells and crystals, but at level n + 1 the entities characteristic of this level are indistinguishably and perfectly identical, for example the ions that are the constituents of crystals. Every crystal is unique but the entities in the scientific representation of that crystal are treated as if they all were perfectly alike. As it is said in legal contexts they are fungibles, any one will do. There is nothing the world we live in that is perfectly identical to anything else – neither galaxies, nor planets, nor organisms, nor snowflakes. Fungibles, like monetary ‘values’, exist in an imaginary world invented by people. This is not to say that changing relations between fungibles cannot have real world consequences as in international exchange rates when they are linked to commodities.

What then is the ontological status of ‘perfect particles’? Surely there are no such beings in the world we inhabit. They are not real entities. Yet they play a central role in sciences like physics and chemistry, as well as in sociology and experimental psychology. According to the Oxford Dictionary a fungible is ‘an instance of an item that is replaceable by another item mutually interchangeable’. Many years ago, Michael LockwoodFootnote ²⁰ suggested adopting this concept as the generic term for a characteristic of all kinds of subatomic particles – every electron is taken to be perfectly identical to every other. As far as we know his suggestion was never taken up.

Every sodium ion is exactly qualitatively identical with every other for most but not all chemical contexts. Such entities differ solo numero. But there are no such things in those aspects of the natural world to which we have access. If they do have a role it could be as constituents of working models of physical systems, preferably well-adapted to mathematical treatment. Such perfect beings, abstract analogues of whatever real beings they stand in for, are essential not only to chemistry but to certain social sciences, for example psephology, as necessary for the intelligibility of making a statistical analysis of voting patterns. Every Labour voter is a fungible, from the psephologist's point of view, that is exactly like and so equivalent in any other respect to contemporary idealized voting procedures. One atom of carbon can replace another atom of carbon coming from another part of the molecule, and the dispositions of the complex will not change. In a chemical formula, atoms, and their nuclei and orbital electrons are fungibles. However, quantum chemists know how different the local electronic density may turn to be from a particular nucleus of carbon to another within the same molecule.Footnote ²¹ There are political studies based on attending to individual differences among the members of the electorate. This a different science, social psychology, sustained by different hinges.

Examining the chemical formula of a specific molecule, say ethanol (CH₃CH₂OH), all the atoms of carbon, and all the atoms of hydrogen seem perfectly interchangeable with one another which enables chemists to provide explanations and predictions of chemical properties, and to foresee and carry out new chemical syntheses of hitherto unknown compounds, in short that are iconic models. Given the fungability of their constituents they are to some extent abstractions, not actual stuff. They do not exhaust what the complexes {apparatus-methods-chemicals-surroundings-devices} we can handle can afford. Fungibles exist in schematic structural models, not in the everyday world the fringes of which are the province of natural science.

This analysis enables us to identify clearly how product-constituent projection, an essential part of scientific method, offers the temptation to slip into committing a mereological fallacy. This is when the products of a procedure that must conform to the metaphysics of the observable are taken as actual constituents of the systems under study, when this assumption produces insoluble conceptual puzzles.

The description of the situation suggests further refinement, and especially whenever a relational concept of part is required. Let us take the example of Nuclear Magnetic Resonance – NMRFootnote ²² (many of us have been scanned by an NMR machine). This procedure is based on the fact that when a population of magnetic nuclei is placed in an external magnetic field, they become aligned in a predictable and finite number of orientations. For hydrogen nuclei, protons, there are two orientations. In one orientation, the protons are aligned with the external magnetic field and in the other where they are aligned against the field. The energy difference between the two orientations is not large and can be supplied using energy in the form of a radio wave. When the energy is removed, the energized nuclei relax back to the lower energy state. The fluctuation of the magnetic field associated with this relaxation process can be detected and converted into the peaks we see in an NMR spectrum. Each group of equivalents sets of nuclei of hydrogen gives rise to a particular peak whose position on the spectrum depends upon what surrounds the nuclei at stake within the molecule, and which is relative to a chemical reference, i.e., the tetramethylsylane. In addition, the shape of each signal – that is if it appears as a single signal or a double signal, and so on – depends upon the magnetic coupling with neighboring nuclei of hydrogen.

Different ‘parts’ emerge from the spectrum. Each signal represents a set of nuclei ¹H that are chemically equivalent, according to the ¹H NMR magnetic scale. The system {NMR magnetic field-radiowave method-chemical-surroundings} affords different sets of nuclei of hydrogen. Every signal depends on the locality, that is, on the environment of each particular nucleus of hydrogen within the molecules. The nuclei of hydrogen which were all the same within the chemical formula, that is which were fungibles, are now different when we intervene upon the molecule under study. Their characteristic features are relative to the whole previous system. In addition, chemists can use another kind of NMR, for instance the NMR ¹³C. Groups of equivalents nuclei of ¹³C are now at stake; they constitute new different parts of the molecule. Parts are, thus, constituted by the interaction between the molecule and the apparatus in a particular solvent and relatively to a chemical reference. They are not intrinsic. Changing the mode of access, that is, changing the type of NMR, amounts to changing the kinds of parts that originate from the same molecule.Footnote ²³ Fungibles – interchangeable nuclei of hydrogen or of carbon in our second case – are transformed into affordances. They move from iconic models as heuristic guides or tools for action to the status of stabilized outcomes of an intervention upon chemicals in a complex environment, that is to the status of an affordance.

As we have previously pointed out in the domain of nanochemistry, this instance of affordance taken from NMR spectroscopy, emphasizes that a new metaphysical scheme is required for addressing cases in which structure turns out to be relational, rather than intrinsic. The interest is that this type of dispositions, namely affordances, cannot be detached from the mode of intervention used to act upon a body, in that this mode of intervention constitutively takes part in the phenomenal character of what scientists and engineering technologists are talking about.

6. Iconic Models

So far as we are aware the value of the concept of ‘model’ in understanding the genesis of meanings in theoretical contexts was never shown to be an illusion. The role of models was neglected during the era of ‘logicism’ – the doctrine that the job of the philosophical analyst was to reveal the logical form of discourses, especially apparently puzzling or paradoxical discourses. Hempel's deductive – nomological analysis of explanatory discourse was a prime example of lack of attention to the content characteristic of an explanatory discourse, and to that of modelling activities as well. Indefinitely many formal deductive schemes can be constructed from which to recover a given set of experimental results in propositional form.Footnote ²⁴ How do we identify nomological generalisations? The historical role of iconic models as bearers of content has been to reduce that multiplicity to manageable proportions to be available as guides to research. The study of the variety of models in various sciences and their role was a main feature of philosophy of science in the 1950s and 60s for example by Mary Hesse.Footnote ²⁵ Models were taken to be the main determinants of the meaning of concepts that entered a science as constituents of a theory. We want to revive his idea.

In chemistry, biology, ecology, geology and physics, explanatory models are analogical representations of the generative mechanisms that underlie transformational processes, and are used to extend the reach of hypotheses. Their content is typically created as an analogue of a known mechanism. Ice floes grinding together in the Norwegian spring are analogues, that is iconic models, of tectonic plates. C-hexagons are analogues, that is iconic models of benzene based molecules. In many cases the iconic model is a representation of the causal mechanism that is activated to bring about some change in the state of a system, and so a constituent of the scientific image of the world. It is not that causal mechanism. The world is revealed to us only in terms of dispositions, understood as affordances of whole systems, that is never independent of situations and actors. However, iconic models differ greatly in how rich in content they are,

A current debate in quantum chemistry illustrates this situation very well. The Quantum Theory of Atoms in Molecules (QTAIM) uses the notion of ‘topological atoms’ for describing the constituent of molecules; such atoms are non-overlapping entities leaving no gaps between them.Footnote ²⁶ Paul Popelier has pointed out that each topological atom is endowed with properties it inherits from the molecule of which it is a part, and reflects the features of its particular chemical environment inside the molecule.Footnote ²⁷ The following question then immediately arises – which Popelier asks himself in his own way: Is it possible, then, to find exactly the same atom – that is a fungible – more than once coming from different molecules?

In brief, those topological atoms need the whole molecule to be defined as parts. They can be considered as fungibles from the standpoint of the whole structural formula, or sometimes from a symmetry standpoint, but in chemical manipulations within a molecule they are different from one another. Popelier then shows that it is not possible to cut an atom from one molecule and insert it exactly into a corresponding cavity of another molecule, i.e., that it is impossible to transfer perfectly an atom from one molecule to a different molecule, even if such transferability remains possible to some extent and within certain limits. For instance, supported by the faith that a model reveals the correct degrees of transferabilities, this information can be used to set up a library of atoms, enabling a rapid and accurate construction of large ensembles of atoms such as proteins.Footnote ²⁸

Transferability of atoms, that is interchangeability in our context, is, according to Popelier's turn of phrase ‘an unattainable limit’, that is a heuristic guide for carrying out research programs only. Topological atoms are fungibles when, for pursuing their research, quantum chemists consider transferability to be total and feasible in a particular model. But they do not remain fungibles in other iconic models as soon as chemists need a fine-grained description to address a question. All this debate is about models, their relevance, and their efficacy to solve a problem satisfyingly. It is not about affordances when chemists intervene upon a chemical using other chemicals, specific instruments, or electromagnetic waves.

What does this tell us about their ontological status in our science? We suggest that it underlines the way that while cells are part of the world we are manipulating, electrons are part of a generic model of that world, that the uses of the word ‘electron’ are prima facie for referring to parts of a certain model. Do cells exist was solved by Robert Hooke with his microscope, but looked at this way, do electrons exist is not an empirical question. Instead we should ask does the use of this concept in model building, for example by J. J. Thomson and Niels Bohr, facilitate the advance of chemistry and physics? For the purposes of chemistry ‘electrons’ as fungibles are constituents of iconic models rather than tiny pieces of some mysterious stuff.

We know when our discourses are empirical and when they are model oriented by whether the basic entities referred to in such discourses, taken as individuals, are similar to one another or perfectly identical. In the mathematical description of a model the perfect identity hinge is expressed in the algebra.

Just the same analysis applies to the management of money, from which the concept of ‘fungible’ first came.

7. Summary and concluding remarks

If we choose to carry out our analyses in terms of affordances of natural and cultural complexes, dispositions and causal powers, the resolution of mereological fallacies, fungibles, and iconic models what will the resulting philosophical discourse emphasise? It will display the hinges on which the taken for granted intelligibility of the discourse rests and the trustworthiness of the associated practices and procedures. The aim of philosophical analysis will be to reveal at least some of the proposition-practice doppelgängers. According to this prescription neither propositions nor practices can be treated independently. In turn, this procedure will allow for the possibility for hitherto unexamined propositions to be assessed empirically, and hitherto taken-for-granted practices to be tested for efficacy. Propositional hinges turning out to be false, and their doppelgänger hinge practices turning out to be useless drive forward investigations, whether of the natural world or of human society in a more fruitful way than testing predictions or running experimental programs.

Our approach emphasises the holistic structure of complexes as the bearers of potentialities which can be elicited by the causal powers of agents, natural, human and cultural. An experiment or an investigation or any kind of enquiry is a unity, comprising context, experimenter, apparatus, target of action and much more. The results are attributes in both senses of ‘affordance’ of those complexes, that is what the set up affords or makes possible for a certain actor, and what the actions of that actor bring to light, what the totality affords in the second sense. There are taken for granted procedures which express one or more hinges, as people go about their activities. What are the conditions for the intelligibility of a professional practice? A philosopher should search for their propositional doppelgängers and examine them for their empirical status. They may be found already in the discourse of the relevant sciences, but they may be the result of analyses of presuppositions.

When is an existential inference from a product-constituent sequence not a fallacy? When what is projected is a fungible. There are no fungibles in nature, so the outcome of the projection is either nonsense or an iconic model not to be interpreted as literally a representation of an unobservable realm of nature. We can outflank the second mereological fallacy in the case of electrons by interpreting electron chemistry not as a discovery procedure of something that is there in nature waiting to be revealed, but as a device for constructing models of the inaccessible processes that are the actual mechanisms of many natural processes. To take a simple example: a substance that gives away electrons in a reaction is oxidised, and a substance that gains electrons is reduced. This is a very clear picture, and is taught to school children. The elements of this construction have been created as projections of products of analysis of material stuff as constituents in the course of a very long series of affordance experiments, starting with those of J.J. Thomson.

What can we hope to discover by shaping our knowledge garnering activities in accordance with this scheme? At least the affordances of complexes individuated by interest driven criteria will be progressively revealed. At the same time, the hitherto unexamined presuppositions of ways of acquiring knowledge will be made accessible for critical examination.

We hope to have recommended a philosophical methodology the core concepts of which are ‘hinge’ and ‘affordance’. Building a philosophical practice around them draws in four more concepts; causal power, mereological fallacies and their resolutions, fungibles and iconic models, formal analogues of whatever mechanisms and agencies are at work in the natural and social world, but hidden from view.

It is necessary to consider how a metaphysical scheme and an associated conception of the kind of knowledge that a scientific enquiry can produce can ‘underlie’ a science. Or how a theory of money can underlie an economy or a how a cuisine can underlie a meal. We take the role of philosophy of science or of jurisprudence, or of the culinary arts, not as critical commentary on ways of proposing ontological presuppositions or highest level theoretical premises, nor as formulating laws of nature and their relations to particular instances of phenomena, but as a digging out of the ‘hinges’, that are the tacit elements of a discipline.