ariew, rogier (2009) algumas reflexões sobre thomas kuhn

7/29/2019 ARIEW, Rogier (2009) Algumas reflexões sobre Thomas Kuhn

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SPOTLIGHT ON: THE NATURE OF SCIENTIFIC CHANGE

Some Reflections on Thomas Kuhn’s Account of

Scientific Change

Roger Ariew∗

Thomas Kuhn’s account of scientific change in The Structure of Scientific Revolutions(SSR: Kuhn, 1962) draws some of its inspiration from Kuhn’s previous study, The

Copernican Revolution (CR: Kuhn, 1957). In spite of the significant historiographical

differences between the two works, Kuhn makes continuous use of CR in SSR; he uses

CR as the data for considering scientific revolutions, that is, as a source for historical

detail about one exemplary revolution. In SSR, referring to Copernicus’ Preface to

De Revolutionibus, as ‘one of the classic descriptions of a crisis state’, Kuhn cites

CR, pp. 135 – 143 (Kuhn, 1962, p. 69); later on he quotes from CR for Copernicus’

analysis of crisis in astronomy—that astronomers were unable to explain or observe the

constant length of the seasonal year. Even when Kuhn argues that Copernicus achieved

a scientific revolution, that he was able to substitute a new paradigm for the old, one

incommensurable with it, Kuhn refers back to his previous work. In SSR Kuhn asks us to

consider those ‘who called Copernicus mad because he proclaimed that the earth moved.

They were not either just wrong or quite wrong. Part of what they meant by “earth” was

fixed position’. The footnote to that statement refers to CR, chapters 3, 4, and 7, and

states ‘the extent to which heliocentrism was more than a strictly astronomical issue is

a major theme of the entire book’ (Kuhn, 1962, pp. 149–150). In the Preface to SSR,

Kuhn apologized for the fact that ‘he has said nothing about the role of technological

advances or of external social, economic, and intellectual conditions in the development

of the sciences’, and added, ‘one needs, however, to look no further than Copernicusand the calendar to discover that external conditions may help transform a mere anomaly

into a source of acute crisis’ (Kuhn, 1962, p. x). The footnote to this statement states,

‘these factors are discussed in [CR], pp. 122–132, 270–271’. Kuhn also asserts that

‘explicit consideration of effects like these [external conditions] would not, I think,

modify the main theses developed in [SSR]’ (Ibid.). When discussing the Copernican

crisis, Kuhn reiterates, ‘breakdown of the normal puzzle-solving activity is not, of

∗Department of Philosophy, University of South Florida, USA. E-mail: [email protected]

CENTAURUS 2009: VOL. 51: PP. 294–298;doi:10.1111/j.1600-0498.2009.00153.x

© 2009 John Wiley & Sons A/S.



Kuhn’s Account of Scientific Change 295

course, the only ingredient of the astronomical crisis that faced Copernicus. An extended

treatment would also discuss the social pressure for calendar reform, a pressure that

made the puzzle of precession particularly urgent. . . . But technical breakdown would

still remain at the core of the crisis’ (Kuhn, 1962, p. 69). Thus, even in the seemingly

most psychological-sociological element of SSR —that is, in crisis and the emergence of

scientific theories—Kuhn argues that an internal technical CR-like breakdown would be

at the core of the scientific crisis.

I wish to consider briefly whether modifications in what we know about the aftermath

of the Copernican revolution should necessitate modifications in how we think about

scientific change. Take, for example, the case of Jacques du Chevreul, who taught

mathematics and physics at Paris in the 1620s, and who published a treatise on the Sphere

in 1623; he accepted the new astronomical observations, but rejected the Copernican

and Tychonic systems, maintaining a more traditional Aristotelianism. In his treatise, Du

Chevreul discussed the method of parallax, used in support of the Tychonic position, andthe issue of the parallax of comets, but did not decide the question fully (du Chevreul,

1623, pp. 83–85). He adopted a probabilistic language on questions about the matter

of the heavens and its incorruptibility, inserting a disputation with the ‘neoterics’ who

claimed that the heavens are corruptible, on the basis of such astronomical phenomena

as new stars (that is, novas) and comets. In his replies, again couched in probabilistic

language, Du Chevreul denied the conclusiveness of the moderns’ observations and of

their parallactic measurements. He then followed tradition in dividing the stars into fixed

and wandering stars. Du Chevreul tells us that Plato, Aristotle, and all others to the

present generation observed seven wandering stars or planets: Saturn, Jupiter, Mars, theSun, Venus, Mercury, and the Moon. But he also asserts that Galileo, that preeminent

mathematician, discovered four planets circling around Jupiter and two new planets

concentric to Saturn. Thus, du Chevreul counts thirteen planets agreed by all, that is, six

new ones on top of the seven classically known ones. He further multiplies the count

by noting that others add another 30 new planets circling about the Sun, namely the

sunspots that Jean Tarde calls the Bourbon stars (du Chevreul, 1623, pp. 80–85).

The discoveries acknowledged by du Chevreul entail modifications in the doctrine of

the number of the heavens. According to Aristotle and the Aristotelians, the number of

heavens, distinguished by their different motions, is at least eight; instead, du Chevreul

counts only five planetary heavens: those of Saturn, Jupiter, Mars, the Sun, and the Moon

(du Chevreul, 1623, p. 152). Missing in this count are the heavens for the new planets

and those of Venus and Mercury. Du Chevreul asserts that, as shown by the optical tube,

Mercury and Venus rotate around the Sun, that is, they can be found above, below, and

next to the Sun. Thus, the center of their orbs must be the Sun; any other arrangement

would require the interpenetration of orbs, causing a vacuum—and this is impossible

in nature. According to du Chevreul, only the astronomers of his generation, using an

optical instrument that can detect more stars in the Milky Way and other parts of the

firmament, can see that Venus and Mercury are located next to the Sun, above, and below




296 R. Ariew

it. The orbs of Venus and Mercury rotate around the Sun, within the Sun’s heaven, as

the orb of the Moon rotates around the Earth (du Chevreul, 1623, pp. 153–154). The

situation is similar to that of Galileo’s stars around Jupiter and the two ‘planets’ circling

Saturn. The same is true for the thirty Bourbon planets or ‘shadows’ around the Sun. Du

Chevreul’s five heavens are, in order: (1) That of the Moon. (2) Of the Sun, consisting of

the Sun itself in the middle of its heaven, surrounded by the Bourbon stars, Mercury and

Venus. (3) Of Mars. (4) Of Jupiter surrounded by the four Medicean stars. And (5) Of

Saturn, in the middle of which Saturn sits, with two concentric orbs or satellites.

It is not difficult to see that du Chevreul as the legitimate heir such to scholastics

as Christopher Clavius: he managed to accept the observations made by Galileo in

1610–1613 with the assistance of the telescope, but did not regard these phenomena

as evidence for either the Copernican or the Tychonic system. He accepted Galileo’s

observations from more or less within the framework of Aristotelian cosmology, as

received before 1610. This is made quite clear in his chapter on eccentric and epicyclicorbs. There, he argued for the necessity of eccentrics and epicycles and formally rejected

Tycho’s view of the universe. He asserted that Mars cannot be below the Sun, as Tycho

would have it, because that would make the heavens permeable and go against the

appearances (du Chevreul, 1623, pp. 153–154). Further, in his section on the matter of

the world, he denied the kind of language the followers of Tycho used, that the stars

wander in the heavens like fish swimming in water. Tycho’s measurement of the parallax

of the comet of 1577 did not settle the matter for du Chevreul; it did not require him

to think of the planetary heavens as liquid and permeable. In his lectures on Aristotle’s

Meteorology, he continued to claim that comets are sublunary flames.One might conclude that du Chevreul looks very much like one of Kuhn’s practitioners

of normal science, a participant in the older paradigm of astronomy at a time when some

young Turks were giving their allegiances to a new paradigm. However, the situation,

as usual, is more complex. Du Chevreul’s work goes well beyond the definition of

normal science as Kuhn determined it (see Kuhn, 1962, p. 34 for the kinds of activities

Kuhn thinks are typical of normal science). When Kuhn wishes to talk about revolution,

particularly the Copernican revolution, the language he uses to express it fits better with

what du Chevreul accomplished than that of normal science. In SSR, Kuhn describes the

radical transformation in seeing that occurs in the aftermath of a revolution by producing a

fictive speech delivered by an undetermined ‘convert’: ‘Looking at the moon, the convert

to Copernicanism does not say “I used to see a planet, but now I see a satellite.” That

locution would imply a sense in which the Ptolemaic system had once been correct.

Instead, a convert to the new astronomy says, “I once took the moon to be (or saw

the moon as) a planet, but I was mistaken.” That sort of statement does recur in the

aftermath of a scientific revolution’ (Kuhn, 1962, p. 115). Kuhn equates this change in

‘seeing as’ with radical changes of meaning, which characterizes a scientific revolution.

So he adds: ‘The Copernicans who denied its traditional title “planet” to the sun were

not only learning what “planet” meant or what the sun was. Instead, they were changing




Kuhn’s Account of Scientific Change 297

the meaning of “planet” so that it could continue to make useful distinctions in a world

where all celestial bodies, not just the sun, were seen differently from the way they had

been seen before’ (Kuhn, 1962, pp. 128–129; for the development of such an account,

see Anderson et al., 2006). Du Chevreul, of course, exhibits that kind of change of

meaning (and ontology) in his astronomy. Du Chevreul’s convert can also say ‘I once

took Venus and Mercury to be planets (or to have their own planetary heaven), but I

was mistaken.’ Although he doesn’t deny the traditional title of planet to the sun, he can

deny it to Venus, Mercury, the Medicean stars, the Bourbon stars, and the Saturnines.

Du Chevreul (and many others at the time, such as Theophraste Bouju, Libertus

Fromondus, and Jacques Grandamy) accepted Galileo’s novel observations but did not

accept the Copernican or Tychonic system (for more on these figures, see Ariew,

1999). They made significant modifications to their Aristotelianism to accommodate

astronomical novelties. All of them could be said to use Aristotelian principles they

deemed more fundamental to deny Aristotelian tenets they regarded as secondary. As Ihave argued, du Chevreul accepts Venus, Mercury and sunspots as moons of the sun,

together with moons of Jupiter and Saturn, all within a modified Aristotelian system of

eccentrics and epicycles. (I could also have shown that Bouju rejects the Aristotelian

theory of elements and the sphere of fire on Aristotelian grounds and Fromondus and

Grandamy correct Aristotle’s account of comets based Aristotelian principles, making

room for super-lunary comets.) While Du Chevreul and the others could be thought

as normal scientists— in this case, Aristotelians—they made changes that went well

beyond what could be described as the articulation of the Aristotelian paradigm or

exemplar. This criticism of Kuhnian change resembles that of Laudan (1984) in whichLaudan argues that one could hold some of theory, method, or values constant and

make changes in the other; but this account is more basic, since it suggests that one can

make seemingly revolutionary changes in theory without any corresponding changes in

method or values—and, in fact, that this happens fairly frequently (all in the spirit of

‘normal’ science).

In a slightly different context Robert Desgabets, in the second half of the 17 century,

thinking about the various kinds of Cartesians, proposes what he calls the first supplement

to Descartes’ philosophy, in as much as he ‘tries in it to correct Descartes’ thoughts

when it seems to [him] that Descartes has left the right path leading to the truth’; he

compares it with what he calls ‘the second supplement, the new application of Descartes’

incontestable principles to phenomena he had not known, or to truths he had not spoken

of,’ what Cartesians such as Cordemoy, Rohault, de la Forge, Clauberg, and others have

done (Desgabets, 1985, p. 156). The two kinds of Cartesians map very well into two

kinds of normal scientists: the ‘second supplement’ type looks like a Kuhnian normal

scientist; the ‘first supplement’ type is the non-Kuhnian normal scientist I have been

trying to define.

I cannot help myself from bringing up a final point in closing, since du Chevreul’s

work also closes his work with it—the Sphere ends with a chapter on the calendar—and




298 R. Ariew

especially since not so long ago we participated in the very change of the calendar that du

Chevreul stipulated for us almost 400 years before. Unlike Copernicus, du Chevreul had

no problem with the length of the seasonal year. He estimated it to be 365 days, 5 hours,

49 minutes and 16 seconds (du Chevreul, 1623, pp. 216, 225). This means, of course,

that adding an extra day every 4 years would be to compensate too much, namely, by

10 minutes, 44 seconds per year (du Chevreul, 1623, p. 227) or 42 minutes, 56 seconds

every 4 years. If you remove a leap day every 100 years, you would be compensating

too much in the other direction. So you need to add the extra day back every 400 years.

That is what du Chevreul recommended, following Pope Gregory’s advice from 1582.

So the calendar adjustments proposed by du Chevreul are an initial deduction of the

extra days added by the practices of the Julian calendar and the difference resulting from

setting the vernal equinox to March 21, that is, du Chevreul approved of the 10 days

having been dropped in by Catholics October 1582 (du Chevreul, 1623, p. 225). He then

proposed that years 1700, 1800, and 1900 not be leap years, but that there be an extraday added to year 2000 (du Chevreul, 1623, pp. 229–230). That final specification is

exactly what we followed on February 29, 2000.

The adoption by du Chevreul of the Gregorian calendric changes removes from

consideration the best candidate for an internal technical breakdown at the core of

the early modern ‘crisis’ in astronomy (another frequently proposed candidate, the

observation of phases of Venus and Mercury, is also inadequate as crisis provoking,

given du Chevreul’s quick adoption of that astronomical novelty). While Copernicus’s

preface to De Revolutionibus used the language of crisis with respect to the length of the

solar year, there does not seem to have been a genuine technical crisis there—thoughthere might have been a patronage crisis for Copernicus. Calendar reform was not

accomplished by the Copernicans and did not require a scientific revolution. Thus,

paradoxically, the Copernican revolution, that paradigmatic Kuhnian scientific revolution,

does not seem to follow the Kuhnian structure of scientific revolutions.

REFERENCES

Anderson, H., Barker, P. and Chen, X. (2006) The Cognitive Structure of Scientific Revolutions (Cambridge:

Cambridge University Press).

Ariew, R. (1999) Descartes and the Last Scholastics (Ithaca: Cornell University Press).Desgabets, R. (1985) Oeuvres philosophiques in´ edites (Amsterdam: Quadratures).

Du Chevreul, J. (1623) Sphaera (Paris: J. Moreau).

Kuhn, T. S. (1957) The Copernican Revolution (Cambridge: Harvard University Press).

Kuhn, T. S. (1962) The Structure of Scientific Revolutions (Chicago: The University of Chicago Press).

Laudan, L. (1984) Science and Values (Berkeley: University of California Press).


ariew, rogier (2009) algumas reflexões sobre thomas kuhn

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