by Alan Sokal
62 We could go back to the Vienna Circle, but that would take us too far afield. Our analysis in this section is inspired in part by Putnam (1974), Stove (1982) and Laudan (1990b). After our book appeared in French, Tim Budden drew our attention to Newton-Smith (1981), where a similar critique of Popper’s epistemology can be found.
63 Popper (1959).
64 As we shall see below, whether an explanation is ad hoc or not depends strongly upon the context.
65 In this brief summary we have, of course, grossly oversimplified Popper’s epistemology: we have glossed over the distinction between observations, the Vienna-Circle notion of observation statements (which Popper criticizes), and Popper’s notion of basic statements; we have omitted Popper’s qualification that only reproducible effects can lead to falsification; and so forth. However, nothing in the subsequent discussion will be affected by these simplifications.
66 See also Stove (1982, p. 48) for similar quotes. Note that Popper calls a theory ‘corroborated’ whenever it successfully passes falsification tests. But the meaning of this word is unclear; it cannot just be a synonym of ‘confirmed’, for otherwise the entire Popperian critique of induction would be empty. See Putnam (1974) for a more detailed discussion.
67 For example, he writes: ‘The proposed criterion of demarcation also leads us to a solution of Hume’s problem of induction – of the problem of the validity of natural laws. ... [T]he method of falsification presupposes no inductive inference, but only the tautological transformations of deductive logic whose validity is not in dispute.’ (Popper 1959, p. 42)
68 As Laplace wrote: ‘The learned world awaited with impatience this return which was to confirm one of the greatest discoveries that have been made in the sciences...’ (Laplace 1902 [1825], p. 5)
69 For a detailed history, see, for example, Grosser (1962) or Moore (1996, chapters 2 and 3).
70 Let us emphasize that Popper himself is perfectly aware of the ambiguities associated with falsification. What he does not do, in our opinion, is to provide a satisfactory alternative to ‘naive falsificationism’ – that is, one which would correct its defects while retaining at least some of its virtues.
71 See, for example, Putnam (1974). See also the reply of Popper (1974, pp. 993–9) and the response of Putnam (1978).
72 Note that the existence of such ‘dark’ matter – invisible, though not necessarily undetectable by other means – is postulated in some contemporary cosmological theories, and these theories are not declared unscientific ipso facto.
73 The importance of theories in the interpretation of experiments has been emphasized by Duhem (1954 [1914], second part, chapter VI).
74 Let us emphasize that, in the foreword to the 1980 edition, Quine disavows the most radical reading of this passage, saying (correctly in our view) that ‘empirical content is shared by the statements of science in clusters and cannot for the most part be sorted out among them. Practically the relevant cluster is indeed never the whole of science’ (p. viii).
75 As do some of Quine’s related assertions, such as: ‘Any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system. Even a statement very close to the periphery [i.e. close to direct experience] can be held true in the face of recalcitrant experience by pleading hallucination or by amending certain statements of the kind called logical laws.’ (p. 43) Though this passage, taken out of context, might be read as an apologia for radical relativism, Quine’s discussion (pp. 43–4) suggests that this is not his intention, and that he thinks (again correctly in our view) that certain modifications of our belief systems in the face of ‘recalcitrant experiences’ are much more reasonable than others.
76 Astronomers, beginning with Le Verrier in 1859, noticed that the observed orbit of the planet Mercury differs slightly from the orbit predicted by Newtonian mechanics: the discrepancy corresponds to a precession of the perihelion (point of closest approach to the Sun) of Mercury by approximately 43 seconds of arc per century. (This is an incredibly small angle: recall that one second of arc is 1/3600 of a degree, and one degree is 1/360 of the entire circle.) Various attempts were made to explain this anomalous behavior within the context of Newtonian mechanics: for example, by conjecturing the existence of a new intra-Mercurial planet (a natural idea, given the success of this approach with regard to Neptune). However, all attempts to detect this planet failed. This anomaly was finally explained in 1915 as a consequence of Einstein’s general theory of relativity. For a detailed history, see Roseveare (1982).
77 Indeed, the error could have been in one of the additional hypotheses and not in Newton’s theory itself. For example, the anomalous behavior of Mercury’s orbit could have been caused by an unknown planet, a ring of asteroids, or a small asphericity of the Sun. Of course, these hypotheses can and should be subjected to tests independent of Mercury’s orbit; but these tests depend in turn on additional hypotheses (concerning, for example, the difficulty of seeing a planet close to the Sun) that are not easy to evaluate. We are by no means suggesting that one can continue in this way ad infinitum – after a while, the ad hoc explanations become too bizarre to be acceptable – but this process may easily take half a century, as it did with Mercury’s orbit (see Roseveare 1982).
Besides, Weinberg (1992, pp. 93–4) notes that at the beginning of the twentieth century there were several anomalies in the mechanics of the solar system: not only in Mercury’s orbit, but also in the orbits of the Moon and of Halley’s and Encke’s comets. We know now that the latter anomalies were due to errors in the additional hypotheses – the evaporation of gases from comets and the tidal forces acting on the Moon were imperfectly understood – and that only Mercury’s orbit constituted a true falsification of Newtonian mechanics. But this was not at all evident at the time.
78 For example, Weinberg (1992, pp. 90–107) explains why the retrodiction of the orbit of Mercury was a much more convincing test of general relativity than the prediction of the deflection of starlight by the Sun. See also Brush (1989).
79 By way of analogy, consider Zeno’s paradox: it does not show that Achilles will not, in actual fact, catch the tortoise; it shows only that the concepts of motion and limit were not well understood in Zeno’s time. Likewise, we may very well practice science without necessarily understanding how we do it.
80 Let us emphasize that Duhem’s version of this thesis is much less radical than that of Quine. Note also that the term ‘Duhem-Quine thesis’ is sometimes used to designate the idea (analyzed in the previous section) that observations are theory-laden. See Laudan (1990b) for a more detailed discussion of the ideas in this section.
81 For this section, see Shimony (1976), Siegel (1987) and especially Maudlin (1996) for more detailed critiques.
82 We shall also limit ourselves to The Structure of Scientific Revolutions (Kuhn 1962, 2nd ed. 1970). For two quite different analyses of Kuhn’s later ideas, see Maudlin (1996) and Weinberg (1996b, p. 56).
83 Speaking of ‘the image of science by which we are now possessed’ and which is propagated, among others, by scientists themselves, he writes: ‘This essay attempts to show that we have been misled ... in fundamental ways. Its aim is a sketch of the quite different concept of science that can emerge from the historical record of the research activity itself.’ (Kuhn 1970, p.1).
84 Of course, Kuhn does not explicitly deny this possibility, but he tends to emphasize the less empirical aspects that enter into the choice between theories: for example, that ‘sun worship ... helped make Kepler a Copernician’ (Kuhn 1970, p. 152).
85 Note that this assertion is much more radical than Duhem’s idea that observation depends in part on additional theoretical hypotheses.
86 Kuhn (1970, pp. 130–5).
87 Note also that Kuhn’s phrasing – ‘the percentage composition was different’ – confuses facts with our knowledge of them. What changed, of course, is the chemists’ knowledge of (or beliefs about) the percentages, not the pe
rcentages themselves.
88 The historian thus rightly rejects ‘Whig history’: the history of the past rewritten as a forward march toward the present. However, this quite reasonable attitude ought not to be confused with another, and rather dubious, methodological proscription, namely the refusal to use all the information available today (including scientific evidence) in order to draw the best possible inferences concerning history, on the pretext that this information was unavailable in the past. After all, art historians utilize contemporary physics and chemistry in order to determine provenance and authenticity; and these techniques are useful for art history even if they were unavailable in the era under study. For an example of similar reasoning in the history of science, see Weinberg (1996a, p. 15).
89 See, for example, the studies in Donovan et al. (1988).
90 [This note and the two following are added by us.] According to Aristotle, terrestrial matter is made of four elements – fire, air, water and earth – whose natural tendency is to rise (fire, air) or to fall (water, earth) according to their composition; while the Moon and other celestial bodies are made of a special element, ‘aether’, whose natural tendency is to follow a perpetual circular motion.
91 Ever since antiquity, it was observed that Venus is never very far from the Sun in the sky. In Ptolemy’s geocentric cosmology, this was explained by supposing ad hoc that Venus and the Sun revolve more or less synchronously around the Earth (Venus being closer). It follows that Venus should be seen always as a thin crescent, like the ‘new moon’. On the other hand, the heliocentric theory accounts naturally for the observations by supposing that Venus orbits the Sun at a smaller radius than the Earth. It follows that Venus should, like the Moon, exhibit phases ranging from ‘new’ (when Venus is on the same side of the Sun as the Earth) to almost ‘full’ (when Venus is on the far side of the Sun). Since Venus appears to the naked eye as a point, it was not possible to distinguish empirically between these two predictions until telescopic observations by Galileo and his successors clearly established the existence of the phases of Venus. While this did not prove the heliocentric model (other theories were also able to explain the phases), it did give significant evidence in its favour, as well as strong evidence against the Ptolemaic model.
92 According to Newtonian mechanics, a swinging pendulum remains always in a single plane; this prediction holds, however, only with respect to a so-called ‘inertial frame of reference’, such as one fixed with respect to the distant stars. A frame of reference attached to the Earth is not precisely inertial, due to the Earth’s daily rotation around its axis. The French physicist Jean Bernard Léon Foucault (1819–68) realized that the direction of swinging of a pendulum, seen relative to the Earth, would gradually precess, and that this can be understood as evidence for the Earth’s rotation. To see this, consider, for example, a pendulum located at the north pole. Its direction of swing will remain fixed relative to the distant stars, while the Earth rotates underneath it; therefore, relative to an observer on the Earth, its direction of swing will make one full rotation every 24 hours. At all other latitudes (except the equator), a similar effect holds but the precession is slower: for example, at the latitude of Paris (49°N), the precession is once every 32 hours. In 1851 Foucault demonstrated this effect, using a pendulum 67 meters long hung from the dome of the Panthéon. Shortly thereafter, the Foucault pendulum became a standard demonstration in science museums around the world.
93 This essay has thus far been published only in French translation. We thank Professor Maudlin for supplying us with the original English text.
94 It is worth noting that a similar argument was put forward by Feyerabend in the last edition of Against Method: ‘It is not enough to undermine the authority of the sciences by historical arguments: why should the authority of history be greater than that of, say, physics?’ (Feyerabend 1993, p. 271). See also Ghins (1992, p. 255) for a similar argument.
95 This type of reasoning goes back at least to Hume’s argument against miracles: see Hume (1988 [1748], section X).
96 For example, in 1992 he wrote:
How can an enterprise [science] depend on culture in so many ways, and yet produce such solid results? ... Most answers to this question are either incomplete or incoherent. Physicists take the fact for granted. Movements that view quantum mechanics as a turning-point in thought – and that include fly-by-night mystics, prophets of a New Age, and relativists of all sorts – get aroused by the cultural component and forget predictions and technology. (Feyerabend 1992, p. 29)
See also Feyerabend (1993, p. 13, n. 12).
97 See, for example, Chapter 18 of Against Method (Feyerabend 1975). This chapter is not, however, included in the later editions of the book in English (Feyerabend 1988, 1993). See also Chapter 9 of Farewell to Reason (Feyerabend 1987).
98 For example, he writes: ‘Imre Lakatos, somewhat jokingly, called me an anarchist and I had no objection to putting on the anarchist’s mask.’ (Feyerabend 1993, p. vii).
99 For example: ‘the main ideas of [this] essay ... are rather trivial and appear trivial when expressed in suitable terms. I prefer more paradoxical formulations, however, for nothing dulls the mind as thoroughly as hearing familiar words and slogans’ (Feyerabend 1993, p. xiv). And also: ‘Always remember that the demonstrations and the rhetorics used do not express any “deep convictions” of mine. They merely show how easy it is to lead people by the nose in a rational way. An anarchist is like an undercover agent who plays the game of Reason in order to undercut the authority of Reason (Truth, Honesty, Justice, and so on)’ (Feyerabend 1993, p. 23). This passage is followed by a footnote referring to the Dadaist movement.
100 However, we take no position on the validity of the details of his historical analyses. See, for example, Clavelin (1994) for a critique of Feyerabend’s theses concerning Galileo.
Let us note also that several of his discussions of problems in modern physics are erroneous or grossly exaggerated: see, for example his claims concerning Brownian motion (Feyerabend 1993, pp. 27–9), renormalization (p. 46), the orbit of Mercury (pp. 47–9), and scattering in quantum mechanics (pp. 49–50n). To disentangle all these confusions would take too much space; but see Bricmont (1995a, p. 184) for a brief analysis of Feyerabend’s claims concerning Brownian motion and the second law of thermodynamics.
101 For a similar statement, see Feyerabend (1993, p. 33).
102 For example, it is said that the chemist Kekule (1829–96) was led to conjecture (correctly) the structure of benzene as the result of a dream.
103 Feyerabend (1993, pp. 147–9).
104 For example, the anomalous behavior of Mercury’s orbit acquired a different epistemological status with the advent of general relativity (see notes 76–8 above).
105 A similar remark can be made about the classical distinction, also criticized by Feyerabend, between observational and theoretical statements. One should not be naive when saying that one ‘measures’ something; nevertheless, there do exist ‘facts’ – for example, the position of a needle on a screen or the characters on a computer printout – and these facts do not always coincide with our desires.
106 Feyerabend (1987, p. 263).
107 Reproduced in the second and third English editions.
108 For case studies in which scientists and historians explain the concrete mistakes contained in analyses by supporters of the strong programme, see, for example, Gingras and Schweber (1986), Franklin (1990, 1994), Mermin (1996a, 1996b, 1996c, 1997a), Gottfried and Wilson (1997), and Koertge (1998).
109 Barnes and Bloor (1981).
110 One could of course interpret these words as a mere description: people tend to call ‘true’ what they believe. But, with that interpretation, the statement would be banal.
111 This example is adapted from Bertrand Russell’s critique of the pragmatism of William James and John Dewey: see Chapters 24 and 25 of Russell (1961a), in particular p. 779.
112 Barnes and Bloor (1981, p.
22).
113 A similar slippage arises in their use of the word ‘knowledge’. Philosophers usually understand ‘knowledge’ to mean ‘justified true belief’ or some similar concept, but Bloor begins by offering a radical redefinition of the term:
Instead of defining it as true belief – or perhaps, justified true belief – knowledge for the sociologist is whatever people take to be knowledge. It consists of those beliefs which people confidently hold to and live by. ... Of course knowledge must be distinguished from mere belief. This can be done by reserving the word ‘knowledge’ for what is collectively endorsed, leaving the individual and idiosyncratic to count as mere belief. (Bloor 1991, p. 5; see also Barnes and Bloor 1981, p. 22n)
However, only nine pages after enunciating this non-standard definition of ‘knowledge’, Bloor reverts without comment to the standard definition of ‘knowledge’, which he contrasts with ‘error’: ‘[I]t would be wrong to assume that the natural working of our animal resources always produces knowledge. They produce a mixture of knowledge and error with equal naturalness ...’ (Bloor 1991, p. 14).
114 Though one might have qualms about the hyper-scientistic attitude that human beliefs can always be explained causally, and about the assumption that we have at present adequate and well-verified principles of sociology and psychology that can be used for this purpose.
115 Elsewhere, Bloor does state explicitly that ‘Naturally there will be other types of causes apart from social ones which will cooperate in bringing about belief’ (Bloor 1991, p. 7). The trouble is that he fails to make explicit in what way natural causes will be allowed to enter into the explanation of belief, or what precisely will be left of the symmetry principle if natural causes are taken seriously. For a more detailed critique of Bloor’s ambiguities (from a philosophical point of view slightly different from ours), see Laudan (1981); see also Slezak (1994).