G.E.R. Lloyd, “Saving the Appearances, Classical Quarterly, n.s. 28 (1978): 202-222.
Stable URL: http://www.jstor.org/stable/638722
Response
In this article Lloyd seeks to dispel the interpretation, most notably put forth by Pierre Duhem for Lloyd’s purposes, but also by Halma and Wasserstein, that ancient Greek astronomy was essentially “instrumentalist” — that “Greek astronomical theories were devices or fictions put forward purely for the sake of calculation elegance with no claim to correspond with physical reality.” Lloyd first casts aspersions on Duhem’s attempt by pointing out that “saving the appearances” stood for many different methodological positions in ancient natural science but that Duhem took it to mean only that which would serve his purpose (the small amount of background research I did on Duhem has him as an advocate for instrumentalism in his own day, revealing his insistence on the essential instrumentalism of ancient Greek astronomy to be a superficial appeal to classical authority). For Duhem, the “appearance saving” of ancient Greek astronomers meant specifically that they produced conclusions to correspond with observations, but since more than one conclusion could make sense of the observations, the preferable conclusion was the most mathematically simple; its correspondence with observable reality was irrelevant. Wasserstein was even more reductive: “The Greek astronomer in formulating his astronomical theories does not make any statements about physical nature at all. His theories are purely geometric fictions. That means that to save the appearances became a purely mathematical task, it was an exercise in geometry, no more, but, of course, also no less.”
Lloyd claims, in response to Duhem et al.’s insistence, to have the “limited” aim “to examine the foundations, and test the applicability” of the essential instrumentality of Greek astronomy. But Lloyd was being bashful his purpose in this paper was, rather, to nullify this thesis. He is more confident in the paper’s conclusion, in which he described Duhem’s understanding of the classical Greek texts on which his general thesis depended as questionable and at times “certifiably incorrect.” While Lloyd grants that the Greeks recognized a distinction between mathematics and physics, they did not advocate for “a mathematical astronomy divorced from physics” or seek “to liberate astronomy from all the physical conditions imposed on it.”
To achieve this, Lloyd singles out the astronomical writings of Proclus Diadochus, “The Successor” to Plato, and his major commentator. Take the question of the epicycles and eccentrics for example. If Proclus were simply grasping for the first elegant explanation of celestial motion, epicycles and eccentrics will serve nicely. But Proclus is not satisfied, not only do they lack Plato’s explicit approval, but Proclus seems to agonize as to whether they are “mere contrivances” or if they “have real existence.” Duhem washes over all of this, committing three hermeneutic transgressions in the process. His treatment of Proclus’s astronomical views is an overgeneralized gloss; he misrepresents Proclus as siding with the instrumental view of epicycles and eccentrics when he actually criticizes both; and Proclus uses realist assumptions to level those criticisms at the theory of epicycles and eccentrics.
Just as Proclus is desperate to honor the authority of Plato (the great mass of his oeuvre is commentaries of Plato’s works), Duhem seems desperate to lend his late-19th, early-20th century instrumentalism an air of ancient erudite authority, so much so that he was willing to contort Proclus into form, with egregious chiropractic consequences.
Notes
- 202 – “ ‘Saving the appearances’ . . . stood or was made to stand for many different methodological positions in many different branches of ancient natural science.”
- “I have a quite limited aim, to examine the foundations, and test the applicability, of a widespread and influential line of interpretation of ancient Greek astronomy according to which it was essentially, or at least predominantly, what we may call ‘instrumentalist’ in character – that is, broadly speaking, that Greek astronomical theories were devices or fictions put forward purely for the sake of calculations with no claims to correspond with physical reality.”
- Duhem one of the chief proponents of this theory
- 202n3 – “ ‘Instrumentalism’ is defined by Hesse (1967), as follows: ‘Instrumentalists assume that theories have the status of instruments, tools, or calculating devices in relation to observation statements. In this view it is assumed that theories can be used to relate and systematize observation statements and to derive some sets of observation statements (predictions) from other sets (data); but no question of the truth or reference of the theories themselves arises.’”
- 202-3 – “Their aim was simply and solely to ‘save the appearances’, interpreted by Duhem as meaning that they should furnish conclusions that correspond with the observations. It was possible for several different hypotheses to save the same appearances: in that case it was not a question of choosing between them on the grounds of correspondence with physical reality, but merely on the grounds of mathematical simplicity.”
- 204 – “Wasserstein went on to define it positively as follows: ‘The Greek astronomer in formulating his astronomical theories does not make any statements about physical nature at all. His theories are purely geometric fictions. That means that to save the appearances became a purely mathematical task, it was an exercise in geometry, no more, but, of course, also no less.”
- 205 – “[Proclus in Manitius’s text] then goes on to consider each of these two possibilities and to raise difficulties about both . . .. ‘For if [one is to say] that they are only contrived, they have unwittingly gone over from physical bodies to mathematical concepts and given the causes of physical movements from things that do not exist in nature.’ This first difficulty is then followed by a second where he attacks the idea of putting these objects of thought in motion.”
- 206 – “Yet the important point is that in the sequel both Duhem and Halma imply that Proclus opts for the instrumentalist alternative.”
- 210 – “Even in the concluding section of the chapter he criticizes the astronomers for, among other things, not stating those things that it is possible to grasp, the problems that can be resolved, and at the very end of the chapter he again appears to hedge his bets in the final sentence of the work: ‘Yet one must know this much, that among all the hypotheses these are the simplest and most fitting for heavenly bodies, and that they have been contrived to discover the manner of the movements of the stars that are really moved as they appear, so that the measure of what is in them may be grasped.’ Finally, in In Ti. Too he says at one point that epicycles and eccentrics are not in vain, since they enable one to resolve complex movements into simple ones.”
- 210-11 – “There is evidence, in both Hyp. and In Ti., of his desire for a simple account, not just of the movement of the fixed stars, but also of those of the planets, sun and moon. Moreover he knows, or at least the end of the Hypotyposis suggests that he knows, that the simplest hypotheses are eccentrics and epicycles. Yet there are problems, not just the lack of Plato’s authority, but also the question we began with, are they mere contrivances or do they have real existence? Both present difficulties.”
- 211 – “But if the epicycles and eccentrics are simply objects of thought, then one has unwittingly slipped over into mathematics and one cannot account for physical motions by appealing to things that do not exist in nature. Now why should Proclus be dissatisfied with that solution? Surely the chief problem, on that way of taking the epicycles and eccentrics, is simply that a merely instrumentalist account will not do.”
- “Duhem’s interpretation of Proclus, I conclude, is open to criticism on three grounds. First he speaks quite generally of Proclus’ view on astronomical hypotheses. . . . Secondly, as far as the particular text discussing epicycles and eccentrics is concerned, Duhem represents Proclus opting for the instrumentalist view, when in fact he criticizes both that and the realist alternative. Thirdly, the assumptions at work in both cases in that text turn out to be realist ones.”
- 212 – “Yet he does at least state and discuss a distinction between the view that epicycles and eccentrics are mere objects of thought and the view that they have real existence in the spheres in which they are fixed, and that is rare enough, indeed quite exceptional, in ancient texts of whatever period. The other writers whom Duhem and others cite yield no passage in which the general contrast between ‘instrumentalist’ and ‘realist’ astronomy is debated.”
- “The astronomer, therefore, on this reading [of Duhem], is not merely distinct from the physicist, he is not concerned with physical problems at all. Provided the hypotheses allowed the appearances to be saved, his job was done.”
- 215 – “But if the principal commentators cannot be said to support Duhem’s overall thesis, it is now time to turn to his interpretation of the positions of the main astronomical theorists themselves. Of course the chief problem that confronts us is that although we have our Ptolemy, we have none of Apollonius’ astronomy and very little of Hipparchus and Aristarchus. We have Aristotle’s De Caelo and Metaphysics, but not Eudoxus or Callippus. So we are bound to admit that much remains indeterminate in this question. Yet if we can begin where the evidence is solid, we have, at least, or Ptolemy.”
- 215-16 – “Duhem concertrates, rather, on such texts as Syntaxis xiii ch. 2 and iii ch. 4, interpreting these as support for his general thesis about Greek astronomy, and indeed a modern Duhemian might still want to argue that Ptolemy was a sound instrumentalist in the Syntaxis even though he mistakenly adopted a naïve realist position in the Planetary Hypotheses. But to that one must say that although most of the Syntaxis is undoubtedly take up with solving purely mathematical problems, the whole discussion is set very firmly in the framework of certain physical assumptions.”
- 218 – “Moreover Theon is not only a naïve realist himself, but he also represents Greek astronomy as a whole as founded on physics. This comes out clearly in a passage not mentioned by Duhem in which Theon contrasts Babylonian and Egyptian astronomy with Greek in just this respect: the former were merely arithmetical and geometrical, but incomplete because lacking ‘physiologia’, while the Greeks included the latter.”
- 219-20 – “It is now time to take stock of our conclusions, and I must first repeat, with the strongest possible emphasis, that for many of the most important figures in the history of Greek astronomy we are simply not in a position to pronounce definitely on their views either on the status of the various hypotheses they used, or on the more general question of the nature of astronomy and its relation to physics. Where we do have some evidence, however, whether from practicing astronomers or from the major commentators, it often contradicts the line of interpretation advocated so forcefully by Duhem and thereafter echoed by others. So far from the majority of those texts supporting the thesis that Greek astronomers were, in general, not concerned with the truth of their hypotheses and with whether they conformed to the nature of things, those texts tend to provide evidence against that thesis. In the methodological statements of Geminius Theon, and Proclus, and in the actual practice of Ptolemy, we find support for the opposing point of view, that so far from being indifferent to physics the astronomer must take his starting-points from the physicist . . ..”
- 220 – “Yet the important point is surely this: the astronomers’ interest in the mathematics of their problems often did presuppose a concern with the physics and often again did not exclude such a concern.”
- “To conclude: some of the support Duhem claimed for his general thesis from particular texts depends on a questionable, in places I should say certifiably incorrect, understanding of them. Where it is perfectly fair to say that the Greeks distinguished, even contrasted, mathematics and physics, it is an exaggeration to claim they advocated a mathematical astronomy divorced from physics or sought to liberate astronomy from all the physical conditions imposed on it.”
