Forms of Persuasion: Kepler,Galileo,and the Dissemination of Copernicanism

Kepler J. , Gesammelte Werke , ed. by Caspar Max (Munich, 1937–; hereafter JKGW), iv, 286.28–29: “non est opus moneri Academicos (caeteri saltem cogitent) quid sit Positionem suam custodire” (emphasis in original).

See, for example, Ginzburg Carlo , History, rhetoric, and proof (Hanover, NH, 1999).

See Serjeantson Richard W. , “Proof and persuasion”, in Park K. Daston L. (eds), The Cambridge history of science, iii: Early modern science (Cambridge, 2006), 132–75.

Ibid.

Shapiro Barbara J. , A culture of fact: England, 1550–1720 (Ithaca, NY, 2000). See also Shapin Steven , A social history of truth: Civility and science in seventeenth-century England (Chicago, 1994).

Biagioli Mario , Galileo's instruments of credit: Telescopes, images, secrecy (Chicago, 2006), 1.

For other analyses of Kepler's use of rhetorical techniques, see the discussion of the form of Kepler's Apologia in Jardine Nicholas , The birth of history and philosophy of science (Cambridge, 1984); see also the analysis of the rhetorical nature of the Astronomia nova in Voelkel James R. , The composition of Kepler's Astronomia nova (Princeton, 2001); finally, see the investigation of Kepler as humanist in Grafton Anthony , “Humanism and science in Rudolphine Prague: Kepler in context”, in Defenders of the text: The traditions of scholarship in an age of science, 1450–1800 (Cambridge, 1991), 178–203.

Although Edward Rosen argues that “Kepler sent Galileo a book because he had heard about him” (see “Galileo and Kepler: Their first two contacts”, Isis , lvii (1966), 262–4, p. 264), Stillman Drake's assertion that “that up to this time, Kepler had no more heard of Galileo than Galileo of Kepler” fits better with the textual evidence (see “Galileo, Kepler, and their intermediaries”, in Galileo studies: Personality, tradition, and revolution (Ann Arbor, 1970), 123). Upon receiving Galileo's letter acknowledging receipt of Kepler's book, Kepler wrote to Michael Maestlin as follows: “Nuper in Italiam misi 2 exemplari mei opusculi (sive tui potius) quae Gratissimio et lubentissimo animo accepit Paduanus Mathematicus, nomine Galilaeus Galilaeus, uti se subscripsit” (October 1597, JKGW, xiii, no. 75, 119–21). Although Rosen argues that Kepler was merely struck by the repetition of Galileo's full name in its Latin form (Galileus Galileus), it seems more likely that Kepler had simply not heard of Galileo before receiving his letter. Moreover, as Drake points out, Kepler's comment that he sent his books “in Italiam” seems to indicate that he sent them generally to Italy rather than to a specific location (Padua) or person (Galileo).

Galileo to Kepler, 4 August 1597, JKGW , xiii, no. 73, 15–19: “… id autem eo libentius faciam quod in Copernici sententiam multis abhinc annis uenerim, ac ex tali positione multorum etiam naturalium effectuum causae sint a me adinuentae, quae dubio procul per communem hypothesin inexplicabiles sunt.” Although Galileo did not specify the particular natural effects whose causes he had used Copernican theory to determine, Kepler guessed that he referred to the theory of the tides — And noted in a letter to Herwart von Hohenburg that if this was the case, he believed that Galileo was wrong: “… cum nuper Galilaeus Patavinus Mathematicus in literis ad me scriptis testatus esset, se plurimarum rerum naturalium causas ex hypothesibus Copernici rectissime deduxisse, quas alii reddere ex usitatis non possint, neque tamen in specie quicquam commemoraret, ego hoc de maris fluxu suspicatus sum. Sed tamen ubi rem diligentius perpendo, non videmur a Luna discedere debere, quoad rationes fluxuum ex illa deducere quimus: Quod quidem fieri posse existimo …” (26 March 1598, JKGW, xiii, no. 91, 164–71).

Galileo to Kepler, 4 August 1597, JKGW, xiii, no. 73, 19–23: “… multas conscripsi rationes et argumentorum in contrarium euersiones, quas tamen in lucem hucusque proferre non sum ausus fortuna ipsius Copernici praeceptoris nostri perterritus, qui licet sibi apud aliquos immortalem famam parauerit apud infinitos tamen (tantus enim est stultorum numerus) ridendus et explodendus prodijt”.

Ibid., 23–25: “… auderem profecto meas cogitationes promere si plures, qualis tu es, extarent: At cum non sint, huiusmodi negocio supersedebo”.

Ibid., 8–9: “… profecto summopere gratulor tantum me in indaganda ueritate socium habere, adeoque ipsius ueritatis amicum”.

Kepler to Galileo, 13 October 1597, JKGW, xiii, no. 76, 13–16: “sapienter tu et occulte, proposito exemplari tuae personae, mones cedendum universali ignorantiae, nec sese temere ingerendum vel opponendum vulgi doctorum furoribus, qua in re Platonem et Pythagoram, nostros genuinos magistors, sequeris”.

See, for example, Hankins James , Plato in the Italian Renaissance (Leiden, 1990).

Kepler to Galileo, 13 October 1597, JKGW, xiii, no. 76, 16–19: “… cum hoc saeculo, primum a Copernico, deinde a compluribus, et doctissimo quoque mathematicorum, immanis operis initium sit factum, neque hoc iam porro novum sit, terram movere”.

Ibid., 19–20: “… praestiterit fortasse, communibus suffragiis semel impulsum hunc currum continenter ad metam rapere”.

Ibid., 21–23: “… quia rationum pondera vulgus minus librat, authoritatibus illud magis magisque obruere incipiamus, si forte per fraudem ipsum in cognitionem veritatis perducere queamus”.

Ibid., 30–34: “… qui mihi sunt proximi, vulgus hominum est, qui cum haec abstruse, ut aiunt, non capiant, mirantur tamen, nec, credere velint an non, unquam secum ipsi cogitant. Docti mediocriter, quo sunt prudentiores, hoc cautious sese immiscent hisce mathematicorum litibus…”.

See, for example, Frost Michael H. , Introduction to classical legal rhetoric: A lost heritage (Burlington, 2005), 67.

Ibid., 70; see also Serjeantson; “Proof and persuasion” (ref. 3), 145–9.

Kepler to Galileo , 13 October 1597, JKGW , xiii, no. 76, 32–35: “Docti mediocriter, quo sunt prudentiores, hoc cautius sese immiscent hisce mathematicorum litibus; quinimo fascinari possunt, quod expertus loquor, authoritate matheseos peritorum.” It is, perhaps, no coincidence that in his emphasis on deceptive persuasion Kepler invoked the verb fascinare, the technical term for the means by which witches could capture the souls of their victims.

Ibid., 35–37: “… cum audiunt, quas iam habeamus ephemerides, ex Copernici hypothesibus extructas; quicunque hodie scribant ephemerides, Copernicum omnes sequi”.

Ibid., 37–39: “… et cum ab ipsis postulatur ut concedant quod non nisi in mathesi institutis demonstrari possit, phaenomena sine motu terrae consistere no posse”.

Ibid., 41–42: “cumque sint vera, cur non pro irrefutabilibus obtruderentur?”.

Ibid., 48–50: “qua ratione, monstratis literis (quorsum etiam mihi tuae prosunt), opinionem hanc in animis doctorum excitare potest, quasi omnes ubique professores mathematum consentirent”.

Along similar lines, Biagioli argues that Galileo relied upon distance as a crucial device by which his authority could be constructed; he posits “knowledge as constituted through a range of distance-based partial perceptions”. See Biagioli , Instruments of credit (ref. 6), 26.

Kepler to Galileo , 13 October 1597, JKGW, xiii, no. 76, 50–53: “Verum quid fraude opus est? Confide, Galilaee, et progredere. Si bene coniecto, pauci de praecipuis Europae mathematicis a nobis secedere volent: Tanta vis est veritatis”.

Kepler to Duke Frederick of Würrtemberg, 29 February 1596, JKGW , xiii, no. 30, 16–17: “Copernicus (welchem alle berhuembte Astronomi unserer Zeit, an Ptolemaei und Alphonsi statt, nachfolgen)…”.

Michael Maestlin to Duke Frederick of Würrtemberg, 12 March 1596, JKGW , xiii, no. 31, 38–41: “M. Johann Kepler den newen oder von newem auf die ban wider gebrachten hypothesibus Copernici, nachgeht, welcher, wie vor zeiten Aristarchus und andere hochverstendige philosophi, lehrt, das die Sonn sehe centrum mundi immobilis, die Erd aber bewege sich etc”.

Ibid., 45–48: “… werden zwar in allen Schulen die communes et antiquae hypotheses bey der Jugent behalten, und als leichter zu verstehen, wie billich, gelehert: Aber alle Artifices bleiben doch samentlich ben des Copernici demonstrationibus.”.

Likewise, the physical model that Kepler hoped to create for Frederick — First a static model of the nested Platonic solids, and then a model whose motion would represent the Copernican system — Was intended to spread the truth of Copernicanism and induce belief. See Mosley Adam , “Objects of knowledge: Mathematics and models in sixteenth-century cosmology and astronomy”, in Kusukawa Sachicko MacLean Ian (eds), Transmitting knowledge: Words, images, and instruments in early modern Europe (Oxford, 2006), 193–216.

Interestingly, however, Galileo may not have been averse to Kepler's strategy of ‘deceptive’ persuasion. Paul Feyerabend argues that in the Dialogue, “Galileo uses propaganda. He uses psychological tricks in addition to whatever intellectual reasons he has to offer. These tricks are very successful: They lead him to victory. But they obscure the new attitude towards experience that is in the making … they obscure the fact that the experience on which Galileo wants to base the Copernican view is nothing but the result of his own fertile imagination, and that it has been invented. They obscure this fact by insinuating that the new results which emerge are known and conceded by all, and need only be called to our attention to appear as the most obvious expression of the truth”. See his Against method (London, 1993), 65. Maurice Finocchiaro likewise examines the rhetorical and propagandistic elements of the Dialogue, which he sees as “an attempt by verbal means and techniques to induce or increase adherence to Copernicanism”. See his Galileo and the art of reasoning: Rhetorical foundations of logic and scientific method (Dordrecht, 1980), 22.

Shortly thereafter, Kepler obtained a telescope and published his verification of Galileo's results, titled Narratio de Jovis satellitibus (1611). For a translation and detailed analysis of the two texts, see Pantin Isabelle , Discussion avec Le Messager Céleste: Rapport sur l'observation des satellites de Jupiter (Paris, 1993). For an English translation of the Dissertatio, with detailed notes, see Rosen Edward , Kepler's Conversation with Galileo's Sidereal Messenger (New York, 1965).

For a different interpretation of Kepler's relationship with Galileo, and in particular of Kepler's support of Galileo's Sidereus nuncius, see Biagioli , Galileo's instruments of credit (ref. 6). My approach follows Biagoli's depiction of Galileo, as noted above, by emphasizing Kepler's construction of authority. My disagreement with Biagioli's specific interpretation of Kepler's response to the Sidereus nuncius rests primarily on its emphasis on Galileo's prestige at the expense of Kepler's. According to Biagioli, Kepler supported Galileo because by attaching himself to Galileo he would advance his own credit and prestige. Yet as Imperial Mathematician, Kepler's prestige was at this point far greater than that of Galileo. Moreover, Kepler viewed Italian science, and in particular Italian astronomy, as less advanced that the astronomy of Germany; he noted to Galileo, for instance, that he should not be surprised at opposition in Italy, a place “in qua rei tritissimae et apud omnes Astronomos contestatissimae, Parallaxium scilicet, extant oppugnatores loco eminentissimi, eruditionis fama celeberrimi” (Kepler to Galileo, 9 August 1610, JKGW, xvi, no. 584, 101–3).

Drake Stillman (ed.), Discoveries and opinions of Galileo (Garden City, NY, 1957), 23.

Kepler to Magini , 10 May 1610, JKGW, xvi, no. 573, 39–40: “Copernicani sumus uterque; similis simili gaudet”.

JKGW, iv, 285.26–27: “Accipe igitur ex private et Galilaei propria, publicam descriptione factam, publica dicatione iam Tuam”.

Ibid., 286.2–4: “Cum multi sententiam meam super Galilaei nuncio siderio expeterent; satisfacere placuit omnibus hoc operae compendio; ut Epistolam ad Galilaeum missam (magnam quidem festinatione inter occupations necessarias, intra praescriptum diem fusam) publicis typis excriberem”.

Ibid., 286.28–30: “… viros esse clarissimos, doctrina, gravitate, Constantia, supra popularem vanitatem longissime evectos, qui haec de Galilaeo perscribant”.

Ibid., 286.32–33: “Me … Galilaei potissimum movit authoritas, iudicii rectitudine, ingeniique solertia parta”.

Ibid., 290.13–15: “Temerarius forte videri possim, qui tuis assertionibus, nulla propria experientia suffultus tam facile credam: At qui non credam Mathematico doctissimo…”.

Ibid., 290.20–22: “Egone ut Patricio Florentino fidem derogem de iis quae vidit? perspicaci lusciosus? instrumentis ocularibus instructo, ipse nudus et ab hac supellectili inops?” Kepler here referenced not only Galileo's telescope but also his own myopia.

Ibid., 290.20–22.

Ibid., 290.25–27: “An parum hoc fuerit, Magnorum Hetruriae Ducum familiam ludificari, Mediceumque nomen figmentis suis praefigere, planetas interim verso pollicentem?”.

Kepler likely also had personal reasons for emphasizing Galileo's scholarly precedents. He was not pleased that Galileo had neglected to mention any of his own achievements that had contributed to Galileo's work, and wrote to Magini that though he approved of Galileo's book and rejoiced in its claims, “puto tamen (si legas attente) me satis mihi cavisse; et ubi potui ad sua ipsum principia revocasse” ( Kepler to Magini , 10 May 1610, JKGW , xvi, no. 573, 40–41). Likewise, Martin Hasdale noted that while Kepler endorsed Galileo's book, “se medesimo, professando di havere accennato simili cose … et haveva portato sec oil suo libro, per mostrar allo Ambasciatore Sassone il luogo” (Martin Hasdale to Galileo, 15 April 1610, JKGW, xvi, no. 564, 16–19). Finally, Kepler always felt it to be his duty, like any good humanist, to document his sources fully and precisely, and Galileo's failure to give credit where credit was due would have been seen as an omission on his part. Thus Isabelle Pantin notes that Kepler's citation of Galileo's sources was intended to add back to the work the crucial element of dialogue with a textual tradition: Pantin, Discussion avec Le Messager Céleste (ref. 33), p. cv. Yet whatever critique Kepler hoped to convey in his citation of Galileo's sources, he meant it to be mild, and subsumed to his larger goal of supporting Galileo's work and the Copernicanism that underpinned it. This is evident in his distress when his book was misunderstood, as we shall see below, and in the lengths he took to correct the misunderstanding.

JKGW, iv, 291.36–37: “Incredibile multis videtur epichirema tam efficacies perspicilli, at impossibile aut novum nequaquam est”.

Ibid., 291.37–38: “nec nuper a Belgis prodiit, sed tot iam annis antea proditum a Io. Baptista Porta, Magiae naturalis libro”.

Ibid., 292.28–35.

Ibid., 303.34–35: “… confirmatis iis, qui pridem hoc idem tecum asseverabant…”.

Ibid., 305.6–7: “… quod nuperrime tuis oculus deprehendisse ais, sic esse oportere tibi tanto ante praedixerant”.

As Elizabeth Spiller notes, “Kepler's emphasis on established textual evidence clearly works to create a more recognizable scholarly context for Galileo's remarkable claims. If Galileo is anticipated by Pythagoras or supported by Maestlin, he is less likely to be wrong”. See her Science, reading, and Renaissance literature: The art of making knowledge, 1580–1670 (Cambridge, 2004), 119.

Horky Martin to Kepler , 24 May 1610, JKGW, xvi, no. 575, 16–18: “Scio deceptio unde veniat, hanc tu vir doctissime in dissertatione … invenisti”.

Maestlin to Kepler , 7 September 1610, JKGW, xvi, no. 592, 13: “Galileum deplumasti”.

Fugger Georg to Kepler , 16 April 1610, JKGW, xvi, no. 566, 14–15: “Nouit et solet homo ille aliorum pennis hinc inde collectis, uti coruus apud Aesopum se decorare”.

As noted above (ref. 45), the misunderstanding may have had some basis in fact, as Kepler was certainly frustrated by Galileo's failure to cite his sources. Yet he expressed all his allusions to Galileo's predecessors in ways that he hoped would serve to bolster Galileo's credibility, rather than the reverse. Galileo certainly understood Kepler's text as praise, rather than reproach. He wrote to Vinta, the Tuscan minister, that Kepler had “scritto in approbazione di tutte le particole contenute nel mio libro, senza pur contradire o dubitare in una sola minima cosa” ( Galileo to Vinta Belisario , 7 May 1610, JKGW , xvi, no. 572, 3–5). Modern scholars have also overwhelmingly read Kepler's Dissertatio as a favourable document of support for Galileo. See, for instance, Rosen , “Galileo and Kepler” (ref. 8), 264; Field Judith V. , “Cosmology in the work of Kepler and Galileo”, in Galluzzi P. (ed.), Novità celesti e crisi del sapere: Atti del Convegno Internationale di Studi Galileiani (Florence, 1984), 207–15, p. 207; and, in the same collection, Chevalley Catherine , “Kepler et Galilee dans la Bataille du ‘Sidereus Nuncius’”, 167–75, p. 167, who writes that “it seems certain” that Kepler immediately and whole-heartedly agreed with Galileo's claims, and argues that interpreting the Dissertatio in any other way merely gives credence to the claims of Horky and Magini. Michele Camerota, by contrast, notes the many conflicting threads in Kepler's Dissertatio, among them the desire to write a “philosophical history” of the Nuncius, to link it to past work, and to defend Kepler's own work — And concludes that Kepler's true motivations and intentions in the Dissertatio are difficult to discern. See his Galileo Galilei e la cultura scientifica nell'età della Controriforma (Rome, 2004), 177–8.

Maestlin to Kepler , 7 September 1610, JKGW , xvi, no. 592, 11–17: “Egregie sane Tu in tuo scripto (cuius Exemplar a te mihi missum lectu iucundissimum est, pro quo etiam ingentes tibi ago gratias) Galileum deplumasti, videlicet quod non ipse novi huius Perspicilli primus fuerit Autor: Quod ipse non primus in Luna animadverterit impolitam superficiem: Quod non primus Mundo ostendat, plures in coelo stellas, quam quas hactenus in veterum scriptis annotatas habemus: Et quae caetera sunt”.

Ibid., 39–42: “Verum hic Martinus Horky nos hac solicitudine liberat. Qui deceptionem visus animadvertit, non in alio simili, sed in ipsius Galilei perspicillo, ipsumque Autorem suo proprio gladio sic iugulavit”.

Kepler to Galileo , 9 August 1610, JKGW, xvi, no. 584, 33–50: “Miram adolescentis temeritatem Amicitiam hanc, inquam, vix dum spirare visam obscurissime, nece famosissima jugulavit”.

Ibid., 127–30: “Vulgus enim opticarum rationum imperitum, aures libenter accommodat obtrectatori, ex Opticis loquenti: Quia inter coecum et videntem nescit distinguere, gaudetque qualibuscunque imperitiae suae tribunis”.

Ibid., 115–16: “Igitur etsi mecum nondum, quicquam dubito: Dolet tamen me tamdiu destitui testimoniis aliorum, ad fidem caeteris faciendam”.

Ibid., 118–20: “… neminem praeter te hoc jactantem producere possum, quo famam Epistolae meae defendam: In te uno recumbit tota observationis authoritas”.

Ibid., 53–55: “At non ideo recensui, quid simile antea fuerit observatum, ut ipse obtrectaret, sed ut caeteri crederent plurium testimonio”.

Ibid., 74: “Ego fidem Nuncio astruo.” Galileo appeared to see Kepler's efforts in this light as well. In his response to Kepler's letter, he noted that Kepler was “primus, ac fere solus, re minime inspecta, quae tua est ingenuitas, atque ingenii sublimitas, meis assertionibus integram fidem praebueris” ( Galileo to Kepler , 19 August 1610, JKGW, xvi, no. 587, 3–5).

See Serjeantson , “Proof and persuasion” (ref. 3), 147–8.

See Grafton Anthony , What was history? The art of history in early modern Europe (Cambridge, 2007), 96–122.

Kepler to Galileo , 9 August 1610, JKGW, xvi, no. 584, 82–83: “Et vero, non problema philosophicum, sed quaestio juridica facti est, an studio Galilaeus orbem deluserit”.

Ibid., 75–76: “Certamen hoc virtutis est cum vitio: Ego ut bonus vir, de Galilaei affirmatis judico, non cadere in illum tantam nequitiam”.

Ibid., 76–78: “… ille nullo adhuc gustu honestatis, eoque illam susque deque habens, cadere affirmat, ex suo forte ingenio caeteros aestimans”.

Ibid., 80–82: “Quia haec via juris est; ut quilibet praesumatur bonus, dum contrarium non probetur: Quanto magis si circumstantiae fidem fecerint?”.

Ibid., 142–3: “Licebit tibi tamen hanc epistolam publici juris facere, si tua interesse putaveris”.

Villari Rosario , Elogio della dissimulazione: La lotta politica nel Seicento (Rome, 1987).

Though there is some debate as to its true nature; Carlo Ginzburg portrays it as a unified movement (see his Il nicodemismo: Simulazione e dissimulazione religiosa nell'Europa del '500 (Turin, 1970)) while Carlos Eire describes it as a large-scale and heterogeneous attitude (see his “Calvin and Nicodemism: A reappraisal”, The sixteenth century journal, x (1979), 45–69).

Castiglione Baldassare , Il Cortegiano (Venice, 1524).

See Hankins , Plato in the Italian Renaissance (ref. 14), and Allen Don Cameron , Mysteriously meant: The rediscovery of pagan symbolism and allegorical interpretation in the Renaissance (Baltimore, 1970).

See, for example, Prosperi Adriano , “The missionary”, in Villari Rosario (ed.), Baroque personae (Chicago, 1995), 160–94. See also O'Malley John W. (eds), The Jesuits: Cultures, sciences, and the arts, 1540–1773 (Toronto, 1999), in particular “Part Four: Encounters with the other: Between assimilation and domination”, and “Part Five: Tradition, innovation, and accommodation”.