Abstract
The Galilean science of motion was one of the major sources of inspiration of Thomas Hobbes’ mechanical natural philosophy. Already in 1634, at a time when his philosophical career had only just begun, we find Hobbes hunting — in vain — for a copy of the Dialogo sopra i due massimi sistemi del mondo (1632).1 Then, as a tutor of William Cavendish, the later Duke of Devonshire, Hobbes paid a visit to Galileo at Arcetri in 1635. There is an old legend that on this occasion Galileo inspired Hobbes to conceive a system of ethics more geometrico, which is one of those nice but most probably false myths of the history of philosophy.2 Due to his involvement with the Royalist cause in the English Civil war, Hobbes had to spend a long exile in Paris from 164o until 1651. Actually, this was the most productive period in his life. He was able to frequent on a daily basis the circle of Father Marin Mersenne, where Galileo’s new science of motion stood at the centre of attention. In the Mersenne Circle, Hobbes enjoyed the reputation of a good mathematician and interesting philosopher.
Research for this article was made possible through the financial support of the Netherlands Organization for Scientific Research (vwo), grant 200-22-95.
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Hobbes to William Cavendish, London 26 January / 5 February 1634: “My first businesse in London, was to seeke for Galileos dialogues [ ... ] it is not possible to get it for mony; There were but few brought ouer at first, and they that buy such bookes, are not such men as to part with them againe. I heare say it is called in, in Italy, as a booke that will do more hurt to their Religion then all the bookes have done of Luther and Calvin, such opposition they thinke is betweene their Religion, and naturall reason. I doubt not but the translation of it will here be publiquely embraced, and therefore wish extreamely that Dr. Webbe would hasten it;’ Hobbes, The Correspondence [Malcolm], I, p. 19
See Schuhmann, Hobbes. Une Chronique, pp. 46–47.
Mersenne was clearly shocked by some of the bold theses of the work, including the corporeality of the soul. As a consequence, he locked the manuscript away. It was only rediscovered in the twentieth century, still sometimes misleadingly referred to as Anti-White. On De motu, see Schuhmann, “Hobbes dans les publications de Mersenne:’
“Galilaeus, non modo nostri, sed omnium saeculorum philosophus maximus,“ Hobbes, Critique du De Mundo de Thomas White [ Jacquot e.a.] , p. 178. In the Examinatio et emendatio mathematicae hodiernae, Hobbes writes: “Primus qui scripsit de motu quod dignum lectu erat, fuit Galilaeus,” Hobbes, Opera Latina [Molesworth], Iv, p. 84.
“Galilaeus primus aperuit nobis Physicae universae portam primam, naturam motus,” Hobbes, De corpore [Schuhmann], p. 3. Here Hobbes paraphrases a statement made by Galileo in the 3rd Day of the Discorsi (Theorema II, Corollarius I De motu naturaliter accelerato): “[...1 the Author, who will have gone far to open the entrance and portal that has until now been closed to speculative minds;’ Galilei, Two New Sciences [Drake], p. 169.
On Descartes’ account of free fall, see Damerow e.a., Exploring the Limits, pp. 8–67.
See Koyré, Études galiléennes, pp. 304–317 and Palmerino, “Infinite Degrees of Speed.”
See Palmerino, “Infinite Degrees of Speed;’ pp. 327–328.
On this “second Galileo affair;’ see also Galluzzi, “Gassendi e l’affaire Galilée:’
On Hobbes’ relation to the Aristotelian tradition at this point, see Leijenhorst, The Mechanisation, pp. 172–179 and pp. 188–192.
See, for instance, Conimbricenses, In libros Physicorum, bk. 7, ch. 1, q. 1, art. 2, p. 224.
Ibid.
Hobbes, Concerning Body (London, 1656), The English Works [Molesworth], I, p. 109. The latin original reads: ”Motus est continua unius loci relictio et alterius acquisitio;’ Hobbes, De corpore [ Schuhmann ] , p. 87 (= Opera Latina [Molesworth], I, p. 97).
Aristotle, Physics, vII, 243–31.
“Dicendum quippe est magnetem non primo agere in remotum, nec ab eo immediate ferrum trahi, sed communicata corpori medio attrahente qualitate;’ Conimbricenses, In libros Physicorum, bk. 7, ch. 2, q. 1, art. 3, p. 239.
Hobbes, Concerning Body, The English Works [Molesworth], II, p. 43o. The Latin original reads: “ [ ... ] quia movens incorporeum nullum est et vis magnetica quae sit, ignoratur, et quando erit cognita, invenietur esse motus corporis;’ Hobbes, De corpore [Schuhmann], p. 293 (= Opera Latina [Molesworth], I, p. 351).
Hobbes, The English Works [Molesworth], vII, p. 155•
”Motor omnis movet vel pellendo vel trahendo,“ Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.], p. 180. See Aristotle, Physics, vII, 2, 243b16–17, and Gassendi, Epistolae duae de Motu impresso a motore translato: ”Caeterum, cum plures sint modi quibus causa externa movet, constat tarnen omnes ad duos tanquam praecipuas pertinere: impulsionem et attractionem. Age itaque experiamur, an-non motus rerum cadentium sive perpendicularis aliqua esse possit causa seu impellens seu attrahens seu potius impellens et attrahens simula’ Gassendi, Opera omnia, III, pp. 489b-490a.
“Supponamus igitur primum gravia deorsum pelli. Quern igitur gradum velocitatis pulsor gravi impertit ab initio, tali debet grave illud semper descendere, vel minore propter resistentiam aeris, nisi nova accedat impulsio iam descendenti. Quoniam ergo motus gravium descendentium continuo acceleratur, necesse est, si motus ille pulsio sit, ut pellens continuo incumbat praesensque sit cum eodem incremento velocitatis in omni parte aeris quem grave transit, quod imaginabile non est. Non est ergo unum aliquod pellens quod gravia perpetuo sequitur et impellit;’ Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.], p. 181.
On Descartes’ theory of gravity, see Aiton, The Vortex Theory, p. 55 and Overmann, Theories of Gravity, pp. 80–104.
For a detailed analysis of the epistolary exchange between Descartes and Mersenne on this point, see Palmerino, ”Infinite Degrees of Speed;’ pp. 283–295.
Descartes to Mersenne, 29 January 1640: “Je viens de revoir mes Notes sur Galilée, où je n’ay veritablement pas dit que les cors qui descendent ne passent pas par tous les degrez de tardiveté; mais j’ay dit que cela ne se peut determiner sans sçavoir ce que c’est que la pesanteur, ce qui signifie la mesme. [ ... ] Et quand on frappe une boule avec un mail, je ne croy pas que vous pensiez que cette boule, au commencement qu’elle se meut, aille moins vite que le mail; ny enfin que tous les corps qui sont poussez par d’autres, manquent à se mouvoir, dès le premier moment, d’une vitesse proportionée à celle des cors qui les meuvent. Or est-il que, selon moy, la pesanteur n’est autre chose, sinon que les cors terrestres sont poussez reellement vers le centre de la Terre par la matiere subtile, d’où vous voyez aisément la conclusion,” Descartes, Oeuvres [Adam e.a.], III, pp. 9–10
“Caeterum, duo quaedam praemittenda sunt, quae inter alia bene multa magno Galileo debentur. Unum; corpus suopte decidens motu ea ratione accelerari, ut temporibus aequalibus maiora semper spatia pervadat, iuxta proportionem quam habent numeri impares inter se, initio sumpto ab unitate;’ Gassendi, Opera omnia, III, p. 483a. On Hobbes’ relation to Gassendi, see Schuhmann, “Hobbes und Gassendi.“
“Supponamus gravia deorsum trahi. Quod trahit igitur cohaerere fortiter debet cum ipso gravi quod trahitur, quod de aere cohaerente cum lapide durum est affirmare. Pratererea quod trahit, trahi ipsum quoque debet ab alio quod prius trahebatur, et sic continuo usque ad centrum terrae. Ibi vero si quid trahit, id faciet ascendendo, quod est contra naturam gravium;’ Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.],181.
On Kepler’s therory of gravitational attraction, see Overmann, Theories of Gravity, pp. 31–53. On Hobbes’ reaction to Kepler’s theory of magnetism and gravity, see Horstmann, “Ein Baustein;’ p. 147 and 154.
Hobbes, Concerning Body, The English Works [Molesworth], I, p. 434. The Latin original reads: “Virtutem autem magneticam illam sive attractionem et abactionem Terrae fieri arbitretur per species immateriatas. Hoc autem fieri non potest, propterea quod nihil movet nisi corpus motum et contiguum;“ Hobbes, De corpore [Schuhmann], p. 295 (= Opera Latina [Molesworth], I, p. 354).
Hobbes, Concerning Body, The English Works [Molesworth], I, p. 434. The Latin original reads: “Nam si hoc esset, non video, quare ovum ab ovo non attrahetur;” Hobbes, De corpore [Schuhmann], p. 296 (= Opera Latina [Molesworth], I, p. 354).
Gassendi, Opera omnia, III, pp. 521b and 526b. See Schuhmann, “Hobbes und Gassendi,” p. 163.
See Palmerino, “Infinite Degrees of Speed;’ p. 301.
“Neque sufficit dicere emitti ex magnete usque qualitatem quandam in ferrum, nisi dicantur simul emitti insensilia corpuscula quae sint quasi vehiculum eiuscemodi qualitatis. [ . . . ] Emitti ergo ex magnete corpuscula in ferrum debent quae agere in ipsum possint,“ Gassendi, Opera omnia, p. 492a.
Palmerino, “Infinite Degrees of Speed,” pp. 307–308.
The earliest known critique is that formulated by J.B. La Grange in his Principes de la Philosophie of 1675. See Palmerino, “Infinite Degrees of Speed;’ p. 301 n.82.
Freudenthal, “Clandestine Stoic Concepts,” p. 163. The same point is repeated by Osier, “How Mechanical was the Mechanical Philosophy?’” pp. 433–437
“Reliquum ergo est, ut tertio illo modo fiat [sc. descensus gravium], nempe ut sit motus quidam aeris ubique circularis, in quem si quod grave vi ascendat, motus ejus partium internarum, in quo motu consistit essentia ejus, conturbatur propter discordantiam et diversitatem viarum. Unde fit, ut grave semper se restituens perpetuo resiliat, donec perveniat ad centrum terrae, nisi vi prohibeatur;’ Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.], p. 181.
See Leijenhorst, The Mechanisation, pp. 163–165.
“Essentia, sive constitutio uniuscuiusque corporis specifica, id est ea per quam sensibus nostris dissimile apparet caeteris corporibus, in motu quodam consistit partium eius internarum;’ Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.], p. 289.
For examples, see Ariew e.a., “The Cartesian Destiny;’ pp. 316–32o.
Hobbes, Decameron Physiologicum, The English Works [Molesworth], vII, p. 157.
See Leijenhorst, The Mechanisation, p. 189.
Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.], p. 195.
The “cause of hardness and softness” is one of the many topics Hobbes and Descartes quarrelled about in their brief but vehement epistolary polemics organised by Mersenne in 1641. For Hobbes’ position, see his letter to Mersenne, Paris 28 january / 7 february 1641, Hobbes, The Correspondence [Malcolm], p. 62.
Hobbes adopts Kepler’s explanation of the diurnal motion of the earth, viewing the earth as a being that turns itself to the sun, thereby enhancing its “essential motion,” but turning away again so as to let its other parts enjoy the same beneficial effects. Though Hobbes rejects Kepler’s theory of “magnetical virtues,” he does not fully discard the pansensist and animistic elements of this explanation. On this issue, see Horstmann, “Ein Baustein;’ p. 144 and Leijenhorst, The Mechanisation, p. 99.
“Quae ego de hac re dicenda habeo, pauca sunt nec ad ipsam rei medullam pertinentia, sed solummodo praevia quaedam, quibus aliquanto propius ad eius cognitionem accedamus;’ Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.], p. 180.
On Hobbes’ philosophy of mathematics, see Jesseph, Squaring the Circle and Schuhmann, “Geometrie und Philosophie.“
Brandt, Thomas Hobbes’ Mechanical Conception, p. 32o.
Jesseph, Squaring the Circle, p. 111.
Ibid., p. 112.
Hobbes, De corpore [Schuhmann], pp. 340–341 (= Opera Latina [Molesworth], II, pp. 414–415).
See Palmerino’s article in this volume.
Hobbes, De corpore [Schuhmann], pp. 342 (= Opera Latina [Molesworth], r, p. 416).
Hobbes, De corpore [Schuhmann], pp. 343 (= Opera Latina [Molesworth], I, p. 417).
Ibid.
Hobbes, Concerning Body, The English Works [Molesworth], I, p. 510. The Latin original reads: “quo id modo fiat, a nemine explicatum est;” Hobbes, De corpore [Schuhmann], p. 341 (= Opera Latina [Molesworth], I, p. 415).
Hobbes, Opéra Latina [Molesworth], Iv, p. 311.
See Hobbes, De corpore [Schuhmann], p. 343. The same theory in found in the Decameron Physiologicum, Hobbes, Opera Latina [Molesworth], Iv, p. 310.
See, for example, Combach, Physica, p. 622: “Appetitus naturalis est, secundum quem unumquodque in id quod est sibi conveniens fertur. Ita, ut quod grave est habet habitudinem ad locum deorsum, quod leves ad locum sursum.” See also Goclenius, Lexicon philosophicum, sub voce “inclinatio”: “Inclinatio est actus in voluntate vel natura. Itaque voluntaria est, vel naturalis. Synonyma fere sunt: inclinatio, connaturalitas, amor seu appetitus naturalis, naturale desiderium, virtus insita, quae proprietas est naturalis formam consequens, ut sunt gravitas, levitas, quibus res ad sua loca naturalia, quibus eae conservantur, tendunt et aliae qualitates, quibus vel conservantur iv t(Eiv α L vel corrumpentibus resistunt.”
Conimbricenses, In libros Physicorum, bk. 7, ch. 1, q. 1, art. 2, p. 224.
“in superioribus videor mihi satis clare demonstrasse initium motus nisi ab externo et moto nullum esse posse. [ ... ] Quare et gravia sursum mota nisi per motum externum dejici non possunt;’ Hobbes, De corpore [Schuhmann], p. 341 (= Opera Latina [Molesworth], I, p. 414).
“Corpori creato attribuere potentiam seipsam movendi, quid aliud est quam creaturas esse dicere quae a Creatore non dependeant?” Hobbes, De corpore [Schuhmann], p. 341 (= Opera Latina [Molesworth], I, p. 415).
Hobbes, Concerning Body, The English Works [Molesworth], I, p. 51o. The Latin original reads: “Praeterea corpora inanimata appetitu suo insito, cum appetitum nullum habeant, conservationis suae causa, quam causam non intelligunt, locum, ubi sunt, deserere et in alium se transferre, cum homo, qui et appetitum habet et intellectum, ne conservandae quidem vitae causa ultra tres quatuorve pedes se attollere saltu potest, perridiculum est;” Hobbes, De corpore [Schuhmann], p. 341 (= Opera Latina [Molesworth], I, pp. 414–415).
Des Chene, Physiologia, pp. 391–393.
“Vitelleschi notes that natural motive powers have three different effects: 1) they move to a proper place when nothing impedes them; 2) they provide a certain tendency (quidam conatus) to motion if something does impede them; 3) they keep the element in its proper place; resisting any attempt to remove it therefrom. [ ... ] But if gravitation is understood properly for a motion downward or for a conatus to such a motion, then the elements do not gravitate — a fact that explains why we do not feel the weight of the air with which we are surrounded;’ Wallace, Prelude to Galileo, p. 116.
“Inquirendum occurrit hac occasione quid sit conatus. Motum omnes sciunt nihil aliud esse praeter loci prions amissionem et posterions acquisitionem continuam, conatum autem esse idem quod motus principium. Manifestum praeterea est partem omnem motus esse motum, principiumque uniuscujusque rei esse primam ejus partem. Unde sequitur conatum omnem esse motum. Quod si quis negaverit idem esse principium et partem primam, dixeritque principium constare in puncto indivisibili, ita ut id quod jam quiescat, possit tamen, dum quiescit, habere in se principium motus, sequetur, ut id quod quiescit, moveri possit ex seipso neque opus habeat, ut aliud accedat moyens, a quo incipiat moveri, contra suiipsius et omnium pene philosophorum sententiam, et praeterea contra experientiam. Vel si quis dixerit principium motus esse poten tiam ad motum sine actu, sequetur conatum non esse actionem neque quicquam efficere, sive ille introrsum sit sive extrorsum. Est itaque conatus motus actualiter, licet exiguus nec oculis manifestus. [ ... ] Conatus ergo in eo consistit, quod conans moveatur: similiter gravia in terra jacentia conari tamen deorsum dicuntur, quia ablato impedimento actu descendunt. Quod si non descenderent, non dicerentur prius conari. [ ...] Omnino igitur conatus est motus actualis vel totius corporis conantis vel partium ejus internarum et invisibilium;’ Hobbes, Critique du De Mundo de Thomas White [Jacquot e.a.], pp. 194–195.
For a more detailed discussion of the genesis of Hobbes’ concept of conatus and its relation to Descartes, see Leijenhorst, The Mechanisation, pp. 196–201.
Hobbes, Concerning Body, The English Works [Molesworth], I, p. 206. The Latin original reads: “Definiemus conatum esse motum per spatium et tempus minus quam quod datur, id est, determinatur sive expositione vel numero assignatur, id est, per punctum et in instanti;” Hobbes, De corpore [Schuhmann], p. 154 (= Opera Latina [Molesworth], I, p. 177).
Brandt, Thomas Hobbes’ Mechanical Conception, pp. 314ff. The following paragraphs summarise Leijenhorst, The Mechanisation, pp. 200–201.
On Galileo’s concept of momentum, see Galluzzi, Momento.
See Jesseph, Squaring the Circle, pp. 76–77.
Bernstein, “Conatus.“ See also Lasswitz, Geschichte der Atomistik, II, pp. 214–215.
On Hobbes’ polemics against Wallis, see Jesseph, Squaring the Circle.
Galluzzi, Momento.
Leijenhorst, The Mechanisation, pp. 196–201.
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Leijenhorst, C. (2004). Hobbes and the Galilean Law of Free Fall. In: Palmerino, C.R., Thijssen, J.M.M.H. (eds) The Reception of the Galilean Science of Motion in Seventeenth-Century Europe. Boston Studies in the Philosophy of Science, vol 239. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-2455-9_9
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