, 24 2020 . 08:55
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-- A number of years ago I wrote How The Laws of Physics Lie. That book was generally perceived to be an attack on realism. Nowadays I think that I was deluded about the enemy: it is not realism but fundamentalism that we need to combat.
My advocacy of realism - local realism about a variety of different kinds of knowledge in a variety of different domains across a range of highly differentiated situations - is Kantian in structure. Kant frequently used a puzzling argument form to establish quite abstruse philosophical positions (O): We have X - perceptual knowledge, freedom of the will, whatever. But without O (the transcendental unity of the apperception, or the kingdom of ends) X would be impossible, or inconceivable. Hence
. The objectivity of local knowledge is my O; X is the possibility of planning, prediction, manipulation, control and policy setting. Unless our claims about the expected consequences of our actions are reliable, our plans are for nought.
Hence knowledge is possible.
What we have done in modern science, as I see it, is to break the connec-tion between what the explanatory nature is - what it is, in and of itself -and what it does. An atom in an excited state, when agitated, emits photons and produces light. It is, I say, in the nature of an excited atom to produce light. Here the explanatory feature - an atom's being in the excited state - is a structural feature of the atom, which is defined and experimentally identified independently of the particular nature that is attributed to it. It is in the nature of the excited atom to emit light, but that is not what it is to be an atom in an excited state. For modern science what something really is - how it is defined and identified - and what it is in its nature to do are separate things.
So even a perfect and complete modern theory would never have the com-plete deductive structure that the Aristotelians envisaged. Still, I maintain, the use of Aristotelian-style natures is central to the modern explanatory pro-gramme. We, like Aristotle, are looking for 'a cause and principle of change and stasis in the thing in which it primarily subsists', and we, too, assume that this principle will be 'in this thing of itself and not per accidens.
The analytic method is closely associated with what we often call Galilean idealisation. Together idealisation and the inference to natures form a familiar two-tiered process that lies at the heart of modern scientific inquiry. First we try to find out by a combination of experimentation, calculation and inference how the feature under study behaves, or would behave, in a particular, highly specific situation. By controlling for or calculating away the gravitational effects, we try to find out how two charged bodies 'would interact if their masses were zero'. But this is just a stage; in itself this information is uninteresting. The ultimate aim is to find out how the charged bodies interact not when their masses are zero, nor under any other specific set of circumstances, but rather how they interact qua charged. That is the second stage of inquiry:
we infer the nature of the charge interaction from how charges behave in these specially selected 'ideal' circumstances.
The key here is the concept ideal On the one hand we use this term to mark the fact that the circumstances in question are not real or, at least, that they seldom obtain naturally but require a great deal of contrivance even to approximate. On the other, the 'ideal' circumstances are the 'right' ones -right for inferring what the nature of the behaviour is, in itself. Focusing on the first aspect alone downplays our problems. We tend to think that the chief difficulties come from the small departures from the ideal that will always be involved in any real experiment: however small we choose the masses in tests of Coulomb's law, we never totally eliminate the gravitational interac-tion between them; in Galilean experiments on inertia, the plane is never perfectly smooth nor the air resistance equal to zero; we may send our experi-ments deep into space, but the effect of the large massive bodies in the universe can never be entirely eliminated; and we can perform them at cryogenic temperatures, but the conditions will never, in fact, reach the ideal.
The problem I am concerned with is not whether we can get the system into ideal circumstances but rather, what makes certain circumstances ideal and others not. What is it that dictates which other effects are to be minimised, set equal to zero, or calculated away? This is the question, I maintain, that cannot be answered given the conventional empiricist account of scientific knowledge. If we consider any particular experiment, it may seem that the equipment we move about, the circumstances we contrive, and the properties we calculate away are ones that can be described without mentioning natures. But in each case, what makes that arrangement of equip-ment in those particular circumstances 'ideal' is the fact that these are the circumstances where the feature under study operates, as Galileo taught, with-out hindrance or impediment, so that its nature is revealed in its behaviour.
Until we are prepared to talk in this way about natures and their operations, to fix some circumstances as felicitous for a nature to express itself and others as impediments, we will have no way of determining which principle is tested by which experiment. It is this argument that I develop in the next section.
An historical illustration: Goethe and Newton So far I have couched the discussion in terms of making inductions from paltry samples, and that is because induction is the method that Humeans should favour for confirming laws. I think, though, that the process is far better understood as one of deduction. We accept laws on apparently slim experimental bases exactly when we can take for granted such strong back-ground assumptions that (given these assumptions) the data plus the descrip-tion of the experimental set-up deductively imply the law to be established.
Probably the most prominent advocate of a deductive method in reasoning from experiment to law is Isaac Newton. It will be helpful to look briefly at Newton's use of the 'crucial experiment' in his theory of light and colours, and more particularly at Goethe's criticisms of it.
Newton's experimentum crucis is described in his first letter in 1671 to the Royal Society18 in which he introduces his theory that white light consists of diverse rays of different refrangibility (that is, they are bent by different amounts when the light passes through a prism) and that colour is a property of the ray which depends on its refrangibility. The work reported in the letter is often taken as a model of scientific reasoning. Thomas Kuhn, for instance, claims that 'Newton's experimental documentation of his theory is a classic in its simplicity.'19 According to Kuhn, the opposition view might eventually have accounted for some of the data that appeared to refute it, 'but how could they have evaded the implications of the experimentum crucisl An innovator in the sciences has never stood on surer ground.'20 It is important to keep in mind that Newton believed that his claims were proven by his experiments. In his letter he maintains, 'The Theory, which I propounded, was evinced by me, not inferring 'tis thus because not otherwise, that is, not by deducing it from a confutation of contrary suppositions but by deriving it from experiments concluding positively and directly.' Or, 'If the Experiments, which I urge, be defective, it cannot be difficult to show the defects; but if valid then by proving the theory they must render all objections invalid.' One last remark to illustrate the steadfastness of Newton's views on the role of the experimentum crucis in proving this claim appears in Newton's letter of 1676,21 four years after his initial report to the Royal Society. This letter concerned the difficulties Anthony Lucas had reported in trying to duplicate Newton's experiments and also some of Lucas' own results that contradicted Newton's claims. Newton replies, 'Yet it will conduce to his more speedy and full satisfaction if he a little change the method he has propounded, and instead of a multitude of things try only the Experimentum Crucis. For it is not number of experiments, but weight to be regarded; and where one will do, what need many?' Goethe's point of view is entirely opposite to Newton's: 'As worthwhile as each individual experiment may be, it receives its real value only when united or combined with other experiments ... I would venture to say that we cannot prove anything by one experiment or even several experiments together.'22 For Goethe, all phenomena are connected together, and it is essen-tial to follow through from each experiment to another that 'lies next to it or derives directly from it'. According to Goethe, 'To follow every single experiment through its variations is the real task of the scientific researcher.' This is illustrated in his own work in optics where he produces long series of 'contiguous' experiments, each of which is suggested by the one before it. The point is not to find some single set of circumstances that are special but rather to lay out all the variations in the phenomena as the circumstances change in a systematic way. Then one must come to see all the interrelated experiments together and understand them as a whole, 'a single piece of experimental evidence explored in its manifold variations'.
Goethe is sharp in his criticisms of Newton. Two different kinds of criti-cism are most relevant here. The first is that Newton's theory fails to account for all the phenomena it should and that is no surprise since Newton failed to look at the phenomena under a sufficient range of variation of circum-stance. Second, Newton's inferences from the experiments he did make were not valid; the experimentum crucis is a case in point. The chief fault which Goethe finds with Newton's inferences is one that could not arise in Goethe's method. Newton selects a single revealing experiment to theorise from; since he does not see how the phenomena change through Goethe's long sequences of experiments, he does not recognise how variation in circumstance affects the outcome: '[Newton's] chief error consisted in too quickly and hastily -- setting aside and denying those questions that chiefly relate to whether external conditions cooperate in the appearance of colour, without looking more exactly into the proximate circumstances/23 The crucial experiment involves refracting a beam of light through a prism, which elongates the initial narrow beam and 'breaks' it into a coloured band, violet at the top, red at the bottom. Then differently coloured portions of the elongated beam are refracted through the second prism. Consider figure 4.2, which is taken from Dennis L. Sepper's study, Goethe contra Newton. In all cases the colour is preserved, but at one end of the elongated beam the second refracted beam is elongated more than it is at the other. In each case there is no difference in the way in which the light falls on the prism for the second refraction. Newton immediately concludes, 'And so the true cause of the length of the image was detected to be no other than that light consists of rays differently refrangible.'24 We should think about this inference in the context of my earlier cursory description of the modern version of the deductive method, called 'bootstrap-ping' by Clark Glymour,25 who has been its champion in recent debates. In the bootstrapping account, we infer from an experimental outcome to a sci-entific law, as Newton does, but only against a backdrop of rather strong assumptions. Some of these assumptions will be factual ones about the spec-ific arrangements made - for example, that the angle of the prism was 63;
some will be more general claims about how the experimental apparatus works - the theory of condensation in a cloud chamber, for instance; some will be more general claims still - for example, all motions are produced by forces; and some will be metaphysical, such as the 'same cause, same effect' principle mentioned above. The same is true of Newton's inference. It may be a perfectly valid inference, but there are repressed premises. It is the repressed premises that Goethe does not like. On Goethe's view of nature, they are not only badly supported by the evidence; they are false. Colours, like all else in Goethe's world,26 are a consequence of the action of opposites, in this case light and darkness:
We see on the one side light, the bright; on the other darkness, the dark; we bring
what is turbid between the two [such as a prism or a semitransparent sheet of paper], and out of these opposites, with the help of this mediation, there develop, likewise in an opposition, colors.27 Newton's argument requires, by contrast, the assumption that the tendency to produce colours is entirely in the nature of the light, and that is why this dispute is of relevance to my point here. As Sepper says, for Newton 'the cause is to be sought only in the light itself.
Let us turn to Newton's reasoning. The argument is plausible, so long as one is not looking for deductive certainty. From Newton's point of view (though not from that of Goethe, who imagines a far richer set of possibilities), the two hypotheses to be decided between are: (a) something that happens involving white light in the prism produces coloured light; or (b) coloured light is already entering the prism in the first place. We can see the force of the argument by thinking in terms of inputs and outputs. Look at what happens to, say, the violet light in the second prism (figure 4.3) and compare this with the production of violet light in the first prism (figure 4.4).
In both cases the outputs are the same. The simplest account seems to be that the prism functions in the same way in both cases: it just transports the coloured light through, bending it in accord with its fixed degree of refrangib-ility.
Consider an analogous case. You observe a large, low building. Coloured cars drive through. Cars of different colours have different fixed turning radii.
You observe for each colour that there is a fixed and colour-dependent angle between the trajectory on which the car enters the building and the trajectory on which it exits; moreover, this is just the angle to be expected if the cars were driven through the building with steering wheels locked to the far left.
Besides cars, other vehicles enter the building, covered; and each time a covered vehicle enters, a coloured car exits shortly afterward. It exists at just that angle that would be appropriate had the original incoming vehicle been a car of the same colour driven through with its steering wheel locked. Two hypotheses are offered about what goes on inside the building. Both hypo-theses treat the incoming coloured cars in the same way: on entering the building their steering wheels get locked and then they are driven through.
The two hypotheses differ, however, about the covered vehicles. The first hypothesis assumes that these, too, are coloured cars. Inside the building they get unwrapped, and then they are treated just like all the other coloured cars.
The second hypothesis is more ambitious. It envisages that the low building contains an entire car factory. The covered vehicles contain raw material, and inside the building there are not only people who lock steering wheels, but a whole crew of Fiat workers and machinery turning raw materials into cars.
Obviously, the first hypothesis is simpler, but it has more in its favour than that. For so far, the second hypothesis has not explained why the manufac-tured cars exit at the angle they do, relative to their incoming raw materials;
and there seems to be no immediate natural account to give on the second story. True, the cars are manufactured with fixed turning radii, but why should they leave the factory at just the same angle relative to the cart that carries in their raw materials as a drive-through does relative to its line of entry? After all, the manufactured car has come to exist only somewhere within the factory, and even if its steering wheel is locked, it seems a peculiar coincidence should that result in just the right exit point to yield the required angle vis-a-vis the raw materials. In this case, barring other information, the first, Newtonian, hypothesis seems the superior. The caveat, 'barring other information', is central, of course, to Goethe's attack. For, as I have already remarked, Goethe was appalled at the small amount of information that Newton collected, and he argued that Newton's claim was in no way adequate to cover the totality of the phenomena. What looks to be the best hypothesis in a single case can certainly look very different when a whole array of different cases have to be considered.
The principal point to notice, for my purpose, is that the argument is not at all deductive. It can only become so if we already presuppose that we are looking for some fixed feature in light itself that will account for what comes out of the prism - something, as I would say, in the nature of light. Any assumption like this is deeply contrary to Goethe's point of view. The first few paragraphs of Newton's letter, before the introduction of the crucial experiment, give some grounds for such an assumption on his part; Goethe makes fun of them:
It is a fact that under those circumstances that Newton exactly specifies, the image of the sun is five times as long as it is wide, and that this elongated image appears entirely in colors. Every observer can repeatedly witness this phenomenon without any great effort.
Newton himself tells us how he wants to work in order to convince himself that no external cause can bring this elongation and coloration of the image. This treatment of his will, as already was mentioned above, be subjected to criticism for we can raise many questions and investigate with exactness, whether he went to work properly and to what extent his proof is in every sense complete. If one analyses his reasons, they have the following form: When the ray is refracted the image is longer than it should be according to the laws of refraction.
Now I have tried everything and thereby convinced myself that no external cause is responsible for this elongation.
Therefore it is an inner cause, and this we find in the divisibility of light. For since it takes up a larger space than before, it must divided, thrown asunder; and since we see the sundered light in colours, the different parts of it must be coloured.
How much there is to object to immediately in this rationale!28 The contrast that I want to highlight is between Newton's postulation of an inner cause in light versus Goethe's long and many-faceted row of experi-ments. Goethe often remarks that he and Newton both claim to be concerned with colours', Newton after all labels his account in the 1671 letter his 'new theory of light and colours'. But, in actuality, Goethe points out, Newton's work is almost entirely about the behaviour of rays - that is, about the inner nature of light. Goethe's experiments often involve light, but it is not light that he studies. The experiments describe entire interacting complexes, such as evening light entering a room through a hole in a white blind on which a candle throws light ('snow seen through the opening will then appear blue, because the paper is tinged with warm yellow by the candlelight'29), or sun-light shining into a diving bell (in this case 'everything is seen in a red light ... while the shadows appear green'30), or a particularly exemplary case for the existence of coloured shadows, a pencil placed on a sheet of white paper between a short, lighted candle and a window so that the twilight from the window illuminates the pencil's shadow from the candle ('the shadow will appear of the most beautiful blue'31). Even when described from the point of view of Goethe's final account of colour formation, in the prism experiments Goethe is not looking at light but rather at light (or darkness)-in-interaction-with-a-turbid-medium.
Newton focuses on his one special experiment and maintains that the account of the phenomena in that experiment will pinpoint an explanation that is generalisable. The feature that explains the phenomena in that situation will explain phenomena in other situations; hence he looks to a feature that is part of the inner constitution of light itself. To place it in the inner constitu-tion is to cast it not as an observable property characteristic of light but rather as a power that reveals itself, if at all, in appropriately structured circum-stances. To describe it as part of light's constitution is to ascribe a kind of permanence to the association: light retains this power across a wide variation in circumstance - indeed, probably so long as it remains light. That is, I maintain, to treat it as an Aristotelian-style nature. This is why Newton, unlike Goethe, can downplay the experimental context. The context is there to elicit the nature of light; it is not an essential ingredient in the ultimate structure of the phenomenon.
Who has dispensed with natures?
My argument in this chapter hinges on a not surprising connection between methodology and ontology. If you want to find out how a scientific discipline pictures the world, you can study its laws, its theories, its models, and its claims - you can listen to what it says about the world. But you can also consider not just what is said but what is done. How we choose to look at the world is just as sure a clue to what we think the world is like as what we say about it. Modern experimental physics looks at the world under precisely controlled or highly contrived circumstance; and in the best of cases, one look is enough. That, I claim, is just how one looks for natures and not how one looks for information about what things do.
Goethe criticises Newton for this same kind of procedure that we use now-adays, and the dispute between them illustrates my point. Newton's conclu-sions in his letter of 1671, as well as throughout his later work in optics, are about the inner constitution of light. I claim that this study of the inner consti-tution is a study of an Aristotelian-style nature and that Newton's use of experiment is suited to just that kind of enterprise, where the experimentum crucis is an especially striking case. The coloured rays, with their different degrees of refrangibility, cannot be immediately seen in white light. But through the experiment with the two prisms, the underlying nature expresses itself in a clearly visible behaviour: the colours are there to be seen, and the purely dispositional property, degree-of-refrangibility, is manifested in the actual angle through which the light is bent. The experiment is brilliantly constructed: the connection between the natures and the behaviour that is supposed to reveal them is so tight that Newton takes it to be deductive.
Goethe derides Newton for surveying so little evidence, and his worries are not merely questions of experimental design: perhaps Newton miscalcu-lated, or mistakenly assumed that the second prism was identical in structure with the first, or Newton takes as simple what is not ... Goethe's disagree-ment with Newton is not a matter of mere epistemological uncertainty. It is rather a reflection of deep ontological differences. For Goethe, all phenomena are the consequence of interaction between polar opposites. There is nothing in light to be isolated, no inner nature to be revealed. No experiment can show with a single result what it is in the nature of light to do. The empiricists of the scientific revolution wanted to oust Aristotle entirely from the new learning. I have argued that they did no such thing. Goethe, by contrast, did dispense with natures; there are none in his world picture. But there are, I maintain, in ours. https://ivanov-p.livejournal.com/241436.html
