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Descartes as Critic of Galileo

  • William R. Shea
Chapter
Part of the The University of Western Ontario Series in Philosophy of Science book series (WONS, volume 14)

Abstract

Descartes was born in 1596 a full generation later than Galileo and the two men never met. Galileo was seventy-three when Descartes’ first book appeared in 1637 and nowhere in his correspondence does he betray any awareness of the younger Frenchman’s existence even though Mersenne sent him a copy of the Discourse de la méthode. Descartes heard of Galileo, of course, for Galileo’s telescopic discoveries of 1610 created a sensation throughout Europe and were even celebrated in a public lecture at the College of La Flèche when Descartes was a student there. Descartes knew Italian, which was taught to their pupils by the Jesuits, but he does not seem to have read Galileo’s Italian works on hydrostatics, the sunspots and the comets that appeared between 1612 and 1623. Between 1623 and 1625, Descartes made an extended trip throughout Italy but he did not call on Galileo who at the time enjoyed the enviable possible of Mathematician and Philosopher to the Granduke of Tuscany. During that period Descartes was wrestling with problems of mathematics and optics and was only marginally interested in the astronomical phenomena that confronted Galileo.

Keywords

Free Fall Simple Machine Virtual Velocity Impetus Theory Astronomical Phenomenon 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Notes

  1. 1.
    Letter to Mersenne, April 1634, in C. Adam and P. Tannery, Oeuvres de Descartes 1897–1913. Reprint. Paris: Vrin, I. 286.Google Scholar
  2. 2.
    Ibid., p. 287.Google Scholar
  3. 3.
    Letter to Mersenne, 14 August 1634, A.T., I, 304. Beeckman thought more kindly of Galileo’s theory: “... puto earn rationem dignam esse consideratione et meis principiis nullo modo adversantem” (Isaac Beeckman, Journal 1604–1634 (ed. by C. De Waard), Vol. III, Martinus Nijhoff, The Hague, 1945, p. 171. Descartes outlines his tidal theory in chapter 12 of Le Monde (A.T., XI, 80–83) and in the fourth part of his Principia Philosophiae (A.T., VIII-1, 232–238). To Mersenne, he confided: “c’est une des choses qui m’a donné le plus de peine à trouver” (letter of November or December 1632, A.T., 1, 261).Google Scholar
  4. 4.
    Ibid., pp. 304–305.Google Scholar
  5. 5.
    A.T., X, 58.Google Scholar
  6. 6.
    A.T., X, 60.Google Scholar
  7. 7.
    A.T., X, 75–77.Google Scholar
  8. 8.
    A.T., X, 58–61.Google Scholar
  9. 9.
    Letter to Paolo Sarpi, 16 October 1604, in A. Favaro (ed.), Opere di Galileo, Barbera, Florence, 1890–1909, X, 115–116.Google Scholar
  10. 10.
    Beeckman never saw that the principle of rectilinear inertia was incompatible with the assumption that circular motion was inertial. The following entry in Beeckman’s diary illustrates the nature of the confusion under which he, as well as Galileo, laboured. “Dictum est mihi hodie qui est dies 11 octob. 1629, Patrem Paulum Servitam Venetum sentire idem quod ego, ut ante saepe patet, de motu, videlicet quicquam semel monetur, id semper moveri nisi impedimentum accedat, eoque probasse aeternitatem motus in coelo a Deo semel motis” (Journal, Vol. III, p. 136). The Venetian Servite is Paolo Sarpi, Galileo’s friend during his stay in Padua. We see how the necessity of explaining the eternal revolution of the heavenly bodies led, in the absence of a mechanical theory such as Descartes’ or a theory of gravitation such as Newton’s, to a failure to grasp the implication of the law of inertia.Google Scholar
  11. 11.
    Letter to Mersenne, 8 October 1629, A.T., I, 27–28.Google Scholar
  12. 12.
    Letter to Mersenne, 13 November 1629, A.T., I. 73.Google Scholar
  13. 13.
    Ibid., pp. 71–72. It is interesting that Descartes who had begun his letter in French switched to Latin, the language in which the impetus theory was normally discussed. Latin provided, as it were, a groove along which thought about motion ran only to smoothly.Google Scholar
  14. 14.
    Ibid., p. 73.Google Scholar
  15. 15.
    See on this question Ferdinand Alquié, La découverte métaphysique de l’homme chez Descartes, Presses Universitaires de France, Paris, 1950.Google Scholar
  16. 16.
    Galileo Galilei, Dialogue Concerning the Two Chief World Systems (transl. by Stillman Drake), Univ. of California Press, Berkeley, 1962, p. 234. In the Opere, VII, 260–261.Google Scholar
  17. 17.
    Discourse de la méthode, A.T., VI, 18–19.Google Scholar
  18. 18.
    Letter to Mersenne, October or November 1631, A.T., I, 228.Google Scholar
  19. 19.
    Letter to Mersenne, 22 June 1637, A.T., I, 392. See also his letter to Mersenne, 11 October 1638, A.T., II, 385.Google Scholar
  20. 20.
    Letter to Mersenne, 16 Oct. 1639, A.T., II, 594. The mechanism whereby the subtle matter exerts pressure on falling bodies is described in Le Monde (A.T., XI, 72–80) and in the fourth part of the Principia Philosophiae (A.T., VIII-1, 212–217).Google Scholar
  21. 21.
    Letter to Mersenne, 11 March 1640, A.T., III, 36.Google Scholar
  22. 22.
    Letter to Mersenne, 29 June 1638, A.T., II, 194.Google Scholar
  23. 23.
    Letter to Mersenne, 23 August 1638, A.T., II, 336.Google Scholar
  24. 24.
    Letter to Mersenne, October 1638, A.T., II, 380.Google Scholar
  25. 25.
    Ibid., pp. 388–389.Google Scholar
  26. 26.
    Letter to Mersenne, 15 May 1634, AX, I, 295.Google Scholar
  27. 27.
    Letter to Mersenne, April 1634, A.T., I, 286.Google Scholar
  28. 28.
    Compendium Musicae A.T., X, 97. Descartes also subscribed to the erroneous belief that the speed of sound was determined by its pitch: “Ce que vous dites que le son aigu s’étend plus viste que le grave est vrai en tout sens; car il est plus viste porté par l’air, à cause que son mouvement est plus prompt; et il est plus viste discerné par l’oreille... (letter to Mersenne, January 1630, A.T., I, 107).Google Scholar
  29. 29.
    Letter to Huygens, 1646, A.T., IV, 678–680. In his notebook of 1619–1621 known as the Cogitationes Privatae, Descartes already noted instructions for an “instrument de musique fait avec une précision mathématique” (A.T., X, 227).Google Scholar
  30. 30.
    Galileo, Opere, II, 517–518.Google Scholar
  31. 31.
    Galileo, Two New Sciences, p. 100. In Opere, VIII, 143.Google Scholar
  32. 32.
    Letter to Mersenne, 11 October 1638, A.T., II, 385.Google Scholar
  33. 33.
    Ibid., pp. 381–382.Google Scholar
  34. 34.
    Ibid., p. 387.Google Scholar
  35. 35.
    Ibid., p. 388.Google Scholar
  36. 36.
    Galileo, Il Saggiatore, Opere, V1, 352.Google Scholar
  37. 37.
    Letter to an Unknown Correspondent, 22 August 1634, A.T., I, 308.Google Scholar
  38. 38.
    Ibid., p. 310. On Galileo’s experiment: “Son experience, pour sçavoir si la lumière se transmet en un instant, est inutile; car les Eclipses de la lune, se rapportant assez exactement au calcul qu’on en fait, le prouvent incomparablement mieux que tout ce qu’on scauroit esprouver sur terre” (A.T., II, 384).Google Scholar
  39. 39.
    Ibid., p. 308. Using Roemer’s determination of the speed of light, which gave eleven minutes as the time required for a ray from the sun to reach the earth, Huygens was able to show why the eclipses of the moon did not provide the reliable test that Descartes believed. (See A.I. Sabra, Theories of Light from Descartes to Newton, Oldbourne, London, 1967, pp. 203 ff.).Google Scholar
  40. 40.
    See Principia Philosophiae, Second Part, act. 19, A.T., VIII-1, 51.Google Scholar
  41. 41.
    Sabra notes that Newton himself adopted the doctrine of instantaneous propagation of pressure through an incompressible medium in Bk. II, Prop. XLIII of the Principia (Sabra, Theories of Light, p. 56).Google Scholar
  42. 42.
    Galileo, Two New Sciences, Opere, VIII, 66.Google Scholar
  43. 43.
    Letter to Mersenne, 11 October 1638, A.T., II, 382–383. In a letter to Galileo, 3 March 1635, Antonio de Ville solved the problem of the two concentric spheres much more clearly by printing out that the motion of the small circle is the outcome of two motions in the same direction, namely (a) the rotation of the small circle on itself, and (b) the motion of translation impacted to it by the large circle (Opere, XVI, 225–227).Google Scholar
  44. 44.
    Galileo, Two New Sciences, Opere, VIII, 75. In the English transl. of Crew and de Salvio, p. 28.Google Scholar
  45. 45.
    Letter to Mersenne, 11 October 1638, A.T., II, 383.Google Scholar
  46. 46.
    Letter to Galileo, 2 October 1634, Opere, XVI, 136–137.Google Scholar
  47. 47.
    Galileo, Il Saggiatore, Opere, Vi, 232.Google Scholar
  48. 48.
    A.T., X, 446.Google Scholar
  49. 49.
    Galileo, Dialogue, Opere VIII, 229–230.Google Scholar
  50. 50.
    Letter to Mersenne, 15 November 1638, A.T., II, 433. Mersenne’s translation, Les méchaniques de Galilée had been published in Paris in 1634.Google Scholar
  51. 51.
    Letter to Mersenne, 12 September 1638, A.T., II, 354.Google Scholar

Copyright information

© D. Reidel Publishing Company, Dordrecht, Holland 1978

Authors and Affiliations

  • William R. Shea
    • 1
  1. 1.McGill UniversityCanada

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