The Conception of Science in Galileo’s Work

  • Ernan McMullin
Part of the The University of Western Ontario Series in Philosophy of Science book series (WONS, volume 14)


It has been remarked more than once that each generation of theorists of science makes of Galileo, the “father of modern science” by customary reckoning, a scientist after its own heart.1 Most recently Paul Feyerabend proposed that: What Galileo did was to let refuted theories support each other, that he built in this way a new world-view which was only loosely (if at all!) connected with the preceding cosmology (everyday experience included), that he established false connections with the perceptual elements of this cosmology which are only now being replaced by genuine theories (physiological optics, theory of continua), and that whenever possible he replaced old facts by a new type of experience which he simply invented for the purpose of supporting Copernicus.2


Causal Explanation Lunar Surface Incline Plane Posterior Analytics Scientific Demonstration 
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  1. 1.
    See, for example, A. C. Crombie, ‘Galilée devant les critiques de la posterité,’ Conference du Palais de la Découverte, Paris, 1956, Section 3.Google Scholar
  2. 2.
    Against Method, London, 1975, p. 160; ‘Problems of Empiricism II’, The Nature and Function of Scientific Theories, (ed. by R. Colodny), Pittsburgh 1970, p. 323.Google Scholar
  3. 3.
    Against Method, pp. 89, 84, 81.Google Scholar
  4. 4.
    Op. cit. p. 89.Google Scholar
  5. 5.
    Preface to the second edition, N. K. Smith translation (London, 1956), p. 14.Google Scholar
  6. 6.
    Kant, loc. cit. Google Scholar
  7. 7.
    Op. cit. p. 154.Google Scholar
  8. 8.
    Philosophy of the Inductive Sciences, London 1947, vol. 2, p. 220.Google Scholar
  9. 9.
    The Science of Mechanics, Chicago 1893, p. 140.Google Scholar
  10. 10.
    See Maurice Clavelin, The Natural Philosophy of Galileo, Cambridge (Mass.), 1974Google Scholar
  11. 10a.
    Dudley Shapere, Galileo: A Philosophical Study, Chicago 1974.Google Scholar
  12. 11.
    Book 3, chapter 3–5.Google Scholar
  13. 12.
    Physics, II, 2, 194a 7.Google Scholar
  14. 13.
    Posterior Analytics, I, 9.Google Scholar
  15. 14.
    I have discussed two of the leading figures in this ‘mathematical’ tradition, in ‘Ptolemy on Saving the Phenomena’, prepared for the XV Intern. Congress for the History of Science, Edinburgh 1977, and ‘Mathematics and Physics in the Work of Alhazen’, Conference on the relations of history and philosophy of science, Jyväskylä (Finland), 1973, Proceedings to appear in Boston Studies in the Philosophy of Science.Google Scholar
  16. 15.
    See J. Gagné, ‘Du quadrivium aux scientiae mediae’, Actes Congr. Intern. de Philosophie Medievale, Montreal 1969, 975–86.Google Scholar
  17. 16.
    This is a recurrent theme in Pierre Duhem’s great work, Le système du monde (Paris, 1913–17, 10 vols.)Google Scholar
  18. 17.
    Posterior Analytics, II, 19.Google Scholar
  19. 18.
    Op. cit. (translated by H. Tredennick), London 1960, 89b, 15–21.Google Scholar
  20. 20.
    Op. cit. 79a, 24.Google Scholar
  21. 21.
    This is done very well by Nicholas Jardine, ‘Galileo’s Road to Truth and the Demonstrative Regress’, Studies Hist. Philos Science 1 (1976), 277–318. He argues that the Paduan regressus was not the foreshadowing of experimental and hypothetical method that Randall claimed it to be, and that in its manner of going from effect to proximate cause and back to effect, it left unresolved the main difficulties in the Aristotelian scheme. He also claims that far from being influenced by this notion of regressus, Galileo rejected it explicitly. This last is too strong a conclusion from the texts he cites, but what is shown is that the analytic procedure described by Galileo in his mechanics is of a different sort (back to axiom rather than to proximate cause), and further, that there is not much evidence of direct influence on his own work of the specifically Paduan version of the oti-dioti problem. We shall show below that in contexts other than the mechanics, however, Galileo relates demonstration to causes rather than to axioms.CrossRefGoogle Scholar
  22. 22.
    As a young man, he wrote a detailed commentary on the Posterior Analytics, the Disputationes de Praecognitione et Demonstratione, in which he followed the ‘oti-dioti’ distinction by reducing scientific demonstration to the usual two kinds, propter quid and quia, insisted that ex suppositione argument could not be regarded as truly scientific, and argued that regressus is needed in physics (unlike mathematics) because physical causes may be less known than their effects, so that one has to work back to cause and then down to effect again to achieve complete demonstration. This work is not included in Favaro’s National Edition of Galileo’s works, and its exact status is still under discussion. See A. C. Crombie, ‘Sources of Galileo’s Early Natural Philosophy’, in Reason, Experiment and Mysticism (ed. by M. L. Righini Bonelli and W. R. Shea), New York, 1975, pp. 157–75.Google Scholar
  23. 23.
    Opere, 8, 190. The Drake translation (Madison, Wis., 1974) will be used; separate page-references to it are unnecessary since it provides the pagination of the National Edition.Google Scholar
  24. 24.
    This is well brought out by E. W. Strong in the chapter on Galileo in his Procedures and Metaphysics, Berkeley 1936.Google Scholar
  25. 25.
    Dialogue, p. 50Google Scholar
  26. 25a.
    Opere, 7, 75. The translation used will be that of Drake (Berkeley, 1953), slightly modified.Google Scholar
  27. 26.
    Dialogue, pp. 50, 328Google Scholar
  28. 26a.
    Opere, 7, 75, 355.Google Scholar
  29. 27.
    Dialogue, pp. 53–4Google Scholar
  30. 27a.
    Opere, 7, 78.Google Scholar
  31. 28.
    Dialogue, p. 406 Google Scholar
  32. 28a.
    Opere, 7, 432.Google Scholar
  33. 30.
    As Crombie reports the contents of this (as yet unpublished) commentary, several odd features emerge (op. cit., pp. 172–3). True knowledge can only be of real beings, unlike the entities of mathematics. Physical sciences which draw upon mathematical principles (the scientiae mediae) do not generate truly scientific demonstration on their own account. It would seem to follow therefore that neither mathematics nor mechanics can of themselves give scientific knowledge. Further, demonstratio quia (oti) is said to demonstrate the existence of an effect, and to begin from true and necessary premisses; as we have seen, this was not Aristotle’s view.Google Scholar
  34. 31.
    Opere, 6, 67.Google Scholar
  35. 32.
    On Mechanics, Drake translation (madison 1960), p. 151Google Scholar
  36. 32a.
    Opere, 2, 159.Google Scholar
  37. 33.
    Op. cit., p. 157Google Scholar
  38. 33a.
    Opere, 2, 165.Google Scholar
  39. 34.
    Discourses, Opere, 8, 127.Google Scholar
  40. 35.
    Dialogue, p. 356Google Scholar
  41. 35a.
    Opere, 7, 383.Google Scholar
  42. 36.
    Loc. cit. Google Scholar
  43. 37.
    Dialogue, p. 103Google Scholar
  44. 37a.
    Opere, 7, 128–9.Google Scholar
  45. 38.
    The Assayer, Drake translation, p. 236Google Scholar
  46. 38a.
    Opere, 6, 281.Google Scholar
  47. 39.
    Discourse on Method (translated by P. J. Olscamp), Indianapolis 1965, Part 6, p. 52.Google Scholar
  48. 40.
    Dialogue, p. 101Google Scholar
  49. 40a.
    Opere, 7, 127Google Scholar
  50. 40b.
    see also Dialogue, pp. 39–40Google Scholar
  51. 40c.
    Opere, 7, 64.Google Scholar
  52. 41.
    Loc. cit. Google Scholar
  53. 42.
    M. Clavelin, The Natural Philosophy of Galileo, Cambridge (Mass.) 1974, p. 390.Google Scholar
  54. 43.
    Op. cit., pp. 395, 409.Google Scholar
  55. 44.
    Op. cit., p. 411.Google Scholar
  56. 45.
    Op. cit., p. 407.Google Scholar
  57. 46.
    Op. cit., p. 411.Google Scholar
  58. 47.
    Op. cit., p. 392.Google Scholar
  59. 48.
    Discourse on Bodies in Water, Salusbury translation, p. 18Google Scholar
  60. 48a.
    Opere, 4, 79.Google Scholar
  61. 49.
    Dialogue, p. 417Google Scholar
  62. 49a.
    Opere, 7, 443.Google Scholar
  63. 50.
    Discourse, Opere, 8, 296.Google Scholar
  64. 51.
    Dialogue, p. 424Google Scholar
  65. 51a.
    Opere, 7, 450.Google Scholar
  66. 52.
    Dialogue, p. 460Google Scholar
  67. 52a.
    Opere, 7, 484.Google Scholar
  68. 53.
    Dialogue, p. 445Google Scholar
  69. 53a.
    Opere, 7, 471.Google Scholar
  70. 54.
    Discourses, Opere, 8, 296.Google Scholar
  71. 55.
    Op. cit., p. 54.Google Scholar
  72. 56.
    Op. cit., p. 266.Google Scholar
  73. 57.
    Op. cit., p. 267.Google Scholar
  74. 58.
    Reply to A. Rocco’s Esercitazioni Filosofiche, Opere, 7, 744.Google Scholar
  75. 58a.
    See also Discourses, Opere, 8, 108–9.Google Scholar
  76. 59.
    Op. cit., p. 731.Google Scholar
  77. 59a.
    See W. R. Shea, Galileo’s Intellectual Revolution, London, 1972, p. 157.Google Scholar
  78. 60.
    Opere, 6, p. 545. Shea, loc. cit. It is interesting that in the Dialogue, he strengthens this by omitting any reference to his having actually performed the experiment. It is as though he wants to underline that for Salviati an experiment would be altogether redundant as confirmation in this case (p. 145; Opere, 7, 171).Google Scholar
  79. 61.
    Opere, 8, 205.Google Scholar
  80. 62.
    Loc. cit. Google Scholar
  81. 63.
    Opere, 8, 207.Google Scholar
  82. 64.
    Opere, 8, 208.Google Scholar
  83. 65.
    Opere, 8, 212.Google Scholar
  84. 66.
    Loc. cit. Google Scholar
  85. 67.
    Opere, 8, 197.Google Scholar
  86. 68.
    On Mechanics, p. 172Google Scholar
  87. 68a.
    Opere, 2, 181.Google Scholar
  88. 69.
    Dialogue, p. 28Google Scholar
  89. 69a.
    Opere, 7, 52.Google Scholar
  90. 70.
    Dialogue, p. 203Google Scholar
  91. 70a.
    Opere, 7, 229.Google Scholar
  92. 71.
    Dialogue, pp. 207–8Google Scholar
  93. 71a.
    Opere, 7, 234.Google Scholar
  94. 72.
    Discourses, Opere, 8, 51.Google Scholar
  95. 73.
    Discourses, Opere, 8, 274.Google Scholar
  96. 74.
    Loc. cit., italics mine.Google Scholar
  97. 75.
    Discourses, Opere, 8, 275.Google Scholar
  98. 76.
    See T. P. McTighe: ‘Galileo’s Platonismi A Reconsideration,’ in Galileo, Man of Science (ed. by E. McMullin), New York 1967, 365–87, and also the Introduction, p. 29.Google Scholar
  99. 77.
    Dialogue, p. 15Google Scholar
  100. 77a.
    Opere, 7, 39.Google Scholar
  101. 78.
    Discourse, Opere, 8, 117 seq.Google Scholar
  102. 79.
    Opere, 18, 12–13; translated in S. Drake, ‘Galileo’s New Science of Motion,’ in Reason, Experiment, and Mysticism, op. cit., p. 156.Google Scholar
  103. 80.
    ‘Galileo and Reasoning ‘ex suppositione’,’ in Boston Studies in the Philosophy of Science (PSA 1974), XXXII, 1976, pp. 79–104. See pp. 81, 95.Google Scholar
  104. 81.
    Op. cit., pp. 99–100.Google Scholar
  105. 82.
    Opere, 17, 90.Google Scholar
  106. 83.
    Op. cit., p. 92.Google Scholar
  107. 84.
    Bodies in Water, pp. 34 seq., Opere, 4, 97 seq.Google Scholar
  108. 84a.
    lodestone and armature, Dialogue, p. 407, Opere, 7, 433.Google Scholar
  109. 84b.
    For a useful survey of the present state of the evidence on the inductive dimension of Galileo’s work, see W. L. Wisan, ‘The New Science of Motion: A study of Galileo’s De Motu Locali,’ Arch. Hist. Exact Science 13 (1974), 103–306; see ‘The Role of Experiment,’ pp. 120–5.CrossRefGoogle Scholar
  110. 85.
    Letter to Ingoli, 1624, Opere, 6, 633; transl. W. R. Shea, op. cit., pp. 148–9.Google Scholar
  111. 85a.
    See also Consideration of the Copernican Hypothesis of 1616, Opere, 5, 356 seq.Google Scholar
  112. 86.
    Op. cit., p. 84.Google Scholar
  113. 87.
    Dialogue, p. 145Google Scholar
  114. 87a.
    Opere, 7, 171.Google Scholar
  115. 88.
    S. Drake, ‘Galileo’s New Science of Motion,’ p. 153.Google Scholar
  116. 89.
    Op. cit., pp. 153–4.Google Scholar
  117. 90.
    See E. McMullin, ‘Structural Explanation,’ American Philosophical Quarterly, 1978, to appear.Google Scholar
  118. 91.
    Discourses, Opere, 8, 202.Google Scholar
  119. 92.
    Loc. cit. Google Scholar
  120. 93.
    Dialogue, p. 234Google Scholar
  121. 93a.
    Opere, 7, 260.Google Scholar
  122. 94.
    Dialogue, p. 481.Google Scholar
  123. 95.
    This leads Wallace to remark (op. cit., p. 98) that Galileo has a new kind of demonstration since it can work in both directions. But this is peculiar to the context of mechanical laws, and would not work elsewhere. His rendering of the argument in symbolic forms as: ‘If q, then if q then p, then p,’ is misleading, since this is not an argument-form: it has no conclusion. For it to have a conclusion both q, and (if q then p) would have to be separately asserted. And at this point the apparently “necessary” character of the argument (given it by the local form of a tautology) would vanish.Google Scholar
  124. 96.
    Discourses, Opere, 8, 50.Google Scholar
  125. 97.
    Letter to Baliani, Opere, 18, 13.Google Scholar
  126. 98.
    In the ‘geometrodynamics’ of J. A. Wheeler, for example.Google Scholar
  127. 99.
    Assayer, p. 241Google Scholar
  128. 99a.
    Opere, 6, 291.Google Scholar
  129. 100.
    See E. McMullin, ‘Structural Explanation,’ section 1.Google Scholar
  130. 101.
    Assayer, pp. 310–1Google Scholar
  131. 101a.
    Opere, 6, 349.Google Scholar
  132. 102.
    Assayer, p. 312Google Scholar
  133. 102a.
    Opere, 6, 351.Google Scholar
  134. 103.
    Assayer, p. 252Google Scholar
  135. 103a.
    Opere, 6, 296.Google Scholar
  136. 104.
    Postil-137 to O. Grassi, Ratio Ponderum Librae et Simbellae, 1626, p. 480. Quoted by Shea, op. cit., p. 100.Google Scholar
  137. 105.
    Discourses, Opere, 8, 66.Google Scholar
  138. 106.
    Dialogue, p. 62Google Scholar
  139. 106a.
    Opere, 7, 86.Google Scholar
  140. 107.
    Loc. cit. Google Scholar
  141. 108.
    This is more fully worked out in the Starry Messenger than in the Dialogue. See Drake translation, pp. 32–40Google Scholar
  142. 108.
    Opere, 3, 63–71.Google Scholar
  143. 109.
    Dialogue, p. 73Google Scholar
  144. 109a.
    Opere, 7, 98.Google Scholar
  145. 110.
    Dialogue, p. 76Google Scholar
  146. 110a.
    Opere, 7, 101.Google Scholar
  147. 111.
    Dialogue, p. 86Google Scholar
  148. 111a.
    Opere, 7, 111.Google Scholar
  149. 112.
    Dialogue, p. 99Google Scholar
  150. 112a.
    Opere, 7, 124.Google Scholar
  151. 113.
    Shea gives a useful account of the methodological issues involved in this controversy in ‘Sunspots and Inconstant Heavens,’ chapter 3, op. cit. Google Scholar
  152. 114.
    First letter to Weiser, Drake, Discoveries and Opinions of Galileo, p. 99Google Scholar
  153. 114a.
    Opere, 5, 106.Google Scholar
  154. 115.
    Op. cit., p. 100Google Scholar
  155. 115a.
    Opere, 5, 108.Google Scholar
  156. 116.
    Op. cit., p. 112Google Scholar
  157. 116a.
    Opere, 5, 133.Google Scholar
  158. 117.
    Op. cit., p. 109Google Scholar
  159. 117a.
    Opere, 5, 118.Google Scholar
  160. 118.
    Dialogue, p. 54Google Scholar
  161. 118a.
    Opere, 7, 79. My italics.Google Scholar
  162. 119.
    Loc. cit. Google Scholar
  163. 120.
    Assayer, p. 331Google Scholar
  164. 120a.
    Opere, 6, 368.Google Scholar
  165. 121.
    Assayer, p. 272Google Scholar
  166. 121a.
    Opere, 6, 313. He notes here that optics has given him a “necessarily conclusive proof.”Google Scholar
  167. 122.
    Discourse on the Comets, Drake translation, p. 50; Opere, 6, 88.Google Scholar
  168. 123.
    Discourse, p. 21Google Scholar
  169. 123a.
    Opere, 6, 51.Google Scholar
  170. 124.
    Discourse, p. 57Google Scholar
  171. Opere, 6, 98.Google Scholar
  172. 125.
    Assayer, p. 260Google Scholar
  173. 125a.
    Opere, 6, 303.Google Scholar
  174. 126.
    Dialogue, p. 114Google Scholar
  175. 126a.
    Opere, 7, 140.Google Scholar
  176. 127.
    See the Introduction to Galileo, Man of Science, pp. 38–41.Google Scholar
  177. 128.
    Dialogue, p. 118Google Scholar
  178. 128a.
    Opere, 7, 144.Google Scholar
  179. 129.
    Dialogue, p. 122Google Scholar
  180. 129a.
    Opere, 7, 148.Google Scholar
  181. 130.
    This is discussed more fully in the Introduction to Galileo, Man of Science, pp. 33–5.Google Scholar
  182. 131.
    Letter to the Grand Duchess, Drake translation, p. 182Google Scholar
  183. 131a.
    Opere, 5, 317Google Scholar
  184. 131b.
    see also Galileo’s letter to P. Dini, 5, 298 seq.Google Scholar
  185. 132.
    Dialogue, pp. 157–8; Opere, 7, 183–4.Google Scholar
  186. 133.
    Against Method, p. 87.Google Scholar
  187. 134.
    Op. cit., p. 85. It is not clear to me why showing these notions (e.g. absolute and relative motion) to be inconsistent with one another if taken as parts of the same paradigm, should not be held to put proper pressure on their user to attempt some kind of paradigm revision. Feyerabend rejects my suggestion to this effect in my ‘History and Philosophy of Science: A Taxonomy of Their Relations,’ Minn. Studies in Phil. of Science 5 (1970), 12–67; see pp. 34–41.Google Scholar
  188. 135.
    As does P. P. Wiener in ‘The Tradition behind Galileo’s Methodology’, Osiris 1 (1936), 733–46.CrossRefGoogle Scholar

Copyright information

© D. Reidel Publishing Company, Dordrecht, Holland 1978

Authors and Affiliations

  • Ernan McMullin
    • 1
  1. 1.University of Notre DameUSA

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