Utente:Distico/Sandbox
SU BAILLY
La vita di Bailly potrebbe essere descritto in termini di duplice attrazione di scetticismo e credenza. Questi furono i due poli tra i quali fluttuava il suo pensiero. Qualche volta, come nell' Éloge de Leibnitz, egli era attratto dallo scetticismo. Altre volte invece, come nell' Histoire de l'astronomie ancienne e nelle Letters a Voltaire, sotto l'influenza di Court de Gébelin, egli lo respinse. A Voltaire scrisse: «Il dubbio deve avere limiti; non tutte le verità possono essere provate come verità matematiche».[1] Bailly sapeva comunque certamente dubitare ed essere scettico quando la ragione lo richiedeva. La partecipazione all'indagine ufficiale sul mesmerismo ne fu una prova, e gli permise anche di dissipare l'illusione che fosse un frère illuminé.
In prima istanza, si sarebbe potuto immaginare che Bailly si potesse disporre a favore del magnetismo animale, affascinato dal concetto, presente nelle teorie di Mesmer, di armonia universale, dalla soluzione semplice di fenomeni complessi, dalla riconciliazione della Terra e le forze celesti, che egli andava cercando. Infatti il suo mentore, Court de Gébelin, aveva abbracciato il magnetismo animale come una nuova "fede" che aveva l'obiettivo di «ristabilire l'armonia primitiva che regnava tra l'uomo e l'universo».[2] Il fatto che un membro dell'altra commissione, Jussieu, pubblicò un parere dissenziente a quello degli altro, era comunque la prova giusto che ad essi fu permesso di operare in completata libertà.
La Fête de la Fédération
Quando iniziò a farsi largo l'idea di organizzare una festa a Parigi, per convocare una federazione di delegati politici e della Garde nationale da tutta la nazione, la Comune di Parigi adottò questi progetto. Si nominò una delegazione, guidata da Bailly, per presentare il progetto all'Assemblea nazionale costituente la quale l'approvò il 5 giugno.[3]
La Fête de la Fédération si tenne il 14 luglio 1790, ad un anno esatto dalla Presa della Bastiglia, e vi parteciparono i rappresentanti di tutte le province della Francia per assistere al solenne giuramento di fedeltà che sarebbe stato pronunciato dal generale La Fayette, da Luigi XVI e da Talleyrand, vescovo di Autun. La cerimonia si svolse al Campo di Marte, dove per l'occasione fu costruito un grande anfiteatro in grado di ospitare 400'000 persone.[4]
Scetticismo e credenza
Many eighteenth-century men called themselves philosophes simply because they had read Voltaire and because they rejected the principles of revealed religion.
Yet they were not skeptics; they.crowded the doorsteps of Mesmer, Cagliostro, and many a lesser charlatan. Chenier, in his "Epitre sur la superstition," has described the type:
Un jeune homme orgueilleux et docte repute, Tout plein de quelque auteur au hasard feuillete, Etonne un cercle entier de sa haute sagesse. II se joue avec grace aux depens de la messe; II plaisante le pape et siffle avec dedain Tous ces reves sacres qu'enfanta le Jourdain. Et puis d'un ton d'ap6tre empese, fanatique, 11 preche les vertus du baquet mnagnetique, Et ces doigts qui de loin savent bien vous toucher Et font signe a la mort de n'oser approcher.1
The particular "superstition" to which Chenier has reference here is mesmerism or, as it was then called, animal magnetism. The year 1784 was a critical one in the uneven history of mesmerism. For the first time, Mesmer's theories and practices were called to the attention of the world at large, and for the first time a scientific attempt was made to evaluate Mesmer's claimed discoveries. The examination of animal magnetism was the work of a royal commission in which Bailly played an important role.
Bailly's life may be described in terms of the dual attraction of skepticism and credulity. These were two poles between which his thinking fluctuated. Sometimes, as in the Eloge de Leibnitz, he was attracted by skepticism. Sometimes, as in the Histoire de l'astronomie ancienne and the letters to Voltaire, under the influence of Court de Gebelin, he was repelled by it. Come è stato detto, la sintesi di questa duplice attrazione è ciò che lui scrisse a Voltaire: "Le doute doit avoir des bornes; toutes les verites ne peuvent pas etre demontrees comme les verites mathematiques." But Bailly had in him nothing of the "jeune homme orgueilleux et docte repute"; he knew how to doubt when reason demanded it. Participation in the official investigation of mesmerism enabled him to dispel the illusion that he was a frere illumine, Condorcet to the contrary notwithstanding.
The year 1784 marked a turning point in Bailly's life in many ways. The contact with the other members of the commission on mesmerism and the clear issues between the physical and metaphysical explanations of a strange phenomenon did a great deal to scotch any illuministic trends in his thought. He never managed to adopt the gentle skepticism of Franklin; he never achieved the purity of reflective thought of Diderot; he never learned to speak up like Condorcet and d'Alembert; lacking a real sense of humor, he tended to see things without nuance; and yet this period marks a new maturity in his thinking and finds him a respected public figure. By the curious workings of chance, Bailly also won the confidence of the government at this time. His writings, which might have shocked a generation earlier, now seemed innocuous. This may be a way of saying that Bailly was behind the times. It is also a way of saying that the whole attitude of the French monarchy was changing rapidly. Despite the influence of Maurepas, the ideas of the philosophes had had interpreters at court in the persons of Turgot, Malesherbes, and Necker, and there was a mood, even in government, for reform. Bailly was to take his first steps as a reformer under the aegis of that government.
After so detailed an account it is appropriate to consider Bailly's place in eighteenth-century thought. Taine held in Les Origines de la France contemporaine that the Revolution was a consequence of French classicism, with its exaggerated confidence in the value of reason. Paradoxically, that confidence became, in course, an unreasonable fetich. In this sense, Freemasonry, illuminism, mesmerism, and other semi-mystic manifestations were not so much reactions to rationalism as an extension of it. Bailly was a consistent rationalist when he substituted vraisemblance for la vérité inaccessible. The urge to demonstrate and the will to believe the undemonstrable were both characteristic of the eighteenth century; Bailly was a good example of this rule. We have seen that Bailly was not an original thinker, but there is indeed nothing new under the sun, and not all merit lies in originality.
Bailly was a synthesist, and the end result of his work differed, therefore, from the bits and pieces of borrowed philosophy which went into its composition. The first and most important influence on Bailly's thought was Newtonian physics. From his first studies with Montcarville to the last page of the history of Indian astronomy, Bailly proved his ability as an astronomer and mathematician and repeatedly affirmed his conviction that natural phenomena could be explained by essentially simple physical laws. He was not merely an observer, and, in astronomy at least, he was not satisfied with empirical evidence. He regarded mathematics and particularly the advances in mathematics made by Descartes, Newton, and Leibnitz as one of the triumphs of modern civilization and the instrument by which the secrets of Nature could be wrested from her. He learned always to accept the simpler of two possible explanations and the explanation which was applicable to more than one phenomenon. This basically scientific procedure was to characterize all his later non-scientific thinking. When, after nearly a decade of application to physical studies, Bailly began to examine the metaphysical philosophy of Leibnitz, he was prepared to believe that scientific precision could be extended to other fields of human knowledge-history, law, language, etc. It was here that he parted company with the skeptical philosophers, who distrusted systematic explanations of immaterial or intangible phenomena. Like Leibnitz (and like Descartes), Bailly fell victim to the hobgoblin of vraisemblance. Where truth was undemonstrable he was prepared to accept the likely, the probable explanation. He proceeded too rapidly from the known into the unknown, projecting hypothetical straight lines where a devious course would have been more in order. From Leibnitz and from Voltaire Bailly learned a new philosophy of history. History was no longer a mere object of curiosity and the chronicling of superficial fact, but a deep source of knowledge and understanding. As he agreed with the philosophes on the didactic purposes of art, so Bailly agreed with them on the didactic purposes of the study of history, which taught a twofold lesson by good precepts and bad examples. Latent in it were universal and enduring physical truths which documented the progress of man from the time of his creation. But in his study of history, Bailly applied the touchstone of simplicity. As in astronomy, he sought the simpler of two explanations and the explanation which would cover more than one fact. This meant generalization and oversimplification. At this juncture in his development, Bailly came under the influence of Court de Gebelin who was traveling in the same general direction. For a few years they worked separately, but along parallel lines, on the interpretation of myth and allegory, in search of a sure key to the past. Bailly's history, like Court de Gebelin's, is the history of humanity rather than of men, of universal laws rather than of specific events. Like Court de Gebelin, Bailly thought he saw at the beginning Order and Truth, a sublime philosophy and a universal language, documenting the philosophers' arguments for the fraternity of man. The eighteenth century was blessed by the rediscovery of these lost truths, and the renascence of the golden age was at hand. There was a fundamental contradiction implicit in Bailly's belief in progress and his devotion to the cause of antiquity. It was, in a sense, the same conflict which existed between his precise Newtonian doctrines and his "esprit de systeme." He found these contradictions resolved in Freemasonry. Whatever their motives, Voltaire and Franklin had, by joining the order, given it the stamp of approval of the philosophes, and Court de Gebelin had found in it the unity and sublimity of the grand ordre. There can be no doubt that Bailly regarded Freemasonry as the resurrection of the guiding principles of the past. If Bailly differed from the point of view of the philosophes, it was perhaps more in temperament than in doctrine. He was neither a skeptic nor an iconoclast. He was conservative in thought as well as deed; he was, until the Revolution, obedient to the monarchy and discreet in his dealings with the church. When he turned to reform, it was the reform sanctioned by authority. It was for these reasons that he was closer to Buffon than to d'Alembert. It would be a gross underestimation of Bailly to conclude that he was spurned by the philosophes because he was incapable of straight thinking. His association with Franklin in the investigation of animal magnetism and his exhaustive reports on the hospitals quickly dispel any such illusions. Nor can we say that it was solely the influence of Franklin or of anyone else that brought him back from his vain rambles among the ancients. In the Essai sur les fables there was a turning point in his thought or, more correctly, an increasing maturity. He began to be aware of the exceedingly complex nature of human activity, and, although he never lost track of his cosmic principles, his later judgments were more sober. Even the Indian astronomy, ill-conceived and largely inferred though it was, was nevertheless based on scientific methods, and its errors are errors of degree, not of order. Perhaps the discovery and publication of Bailly's unfinished manuscripts will some day permit us to trace further this evolution of his thought. Whereas, in the period before the Revolution, Bailly's life was almost synonymous with his works, after April 1789, his sudiden emergence as a public figure shifts the emphasis from words to deeds. We have dealt superficially with these years, partly because they lie beyond the formative period of his thought, partly because they are well documented elsewhere. However, the Revolution represented the acid test of Bailly's philosophizing; it was the moment that every theorist waits for, the moment when he can try the practical application of his ideas. Bailly's ideas did not survive the test for the very reason that they were too diffuse, too general, too simple. Reason did not engender reason, and, while Bailly thought in terms of civic obedience, the mob outside was committing murder and worse. The remarkable aspect of Bailly's public life is not his failure, but the fact that he succeeded so well in coping with the practical problems which were so far removed from his cognizance. There is a wide field yet to be explored in connection with Bailly's influence on his contemporaries and on the generation immediately following. Dimoff has written a detailed and penetrating account of Chenier's indebtedness to Bailly. Similar studies might be done on Shelley, de Maistre, Mme de Stael and possibly Napoleon. We have the testimony of Mary Shelley that the English poet had read and admired Bailly. De Maistre perhaps based his theory of the degradation of man on some of Bailly's historical research. Mme de Stael, who disapproved of Bailly the revolutionary, may owe to Bailly the historian her notions of the "facultes primitives emoussees" which figure in De l'Allermagne. One of Bailly's biographers, Lefevre- Deumier, claimed that Napoleon ordered the assembling of Bailly's manuscripts and a handsome collected edition of his works. Indeed, the evidence seems to be that Bailly's influence did not die out with the Revolution, but carried on well into the Romantic period. Furthermore, the number of translations of Bailly's works suggests a certain influence abroad, especially in Germany. If this influence has disappeared today, it is because we have, to a considerable extent, emerged from the era of philosophic systems which, in attempting to explain too much, explain very little. Scientists and historians, better equipped with factual knowledge, are increasingly reluctant to generalize their findings in cosmic formulae. Yet there is still what Franklin called "a wonderful deal of credulity in the world," and Bailly, who certainly regarded himself as an enemy of superstition, may none the less serve as an object lesson in the subtle dangers of rationalism. Un mensonge vieillit; il devient ennuyeux. I1 prend une autre forme et reparait aux yeux. Pensant le fuir, trompes 'a sa ruse infidele, Nous courons 1'embrasser sous sa forme nouvelle. Nous quittons un prestige, une vaine fureur, Non pour la verite, mais pour une autre erreur. Andre Chenier, "Epitre a Bailly."
Sulle disuguaglianze
Perhaps it was the momentum of work already in hand; perhaps it was a desperate bid for favor; perhaps it was a determination to rise above the political bicker- ing that led Bailly to produce one of his best scientific papers, the "Mémoire sur les inégalités de la lumière des satellites de Jupiter, sur la mesure de leur diamètre, et sur un moyen aussi simple que commode de rendre les observations comparables, en remédiant à la différence des vues et des lunettes."18
Lalande, Laplace, Delambre, Arago-all the astronomers who have evaluated Bailly's work-are in accord on the excellence of this mnemoire. Lalande wrote of it:
Ce travail, plein de sagacité, ne pouvait être fait que par un de nos plus grands astronomes; et je lui disais, dans le temps de sa gloire, que j'aimerais mieux l'avoir fait que d'avoir été le premier sur la liste des présidents des Etats généraux et des maires de Paris, quoique son mérite l'y efit place.19
The time of apparent eclipse of a satellite precedes the time of real eclipse, because the observer sees only the illuminated segment of the satellite. The apparent size of this segment varies with the brilliance of the satellite, the intensity of light on Jupiter, the distance of the satellite at Jupiter's limb, the height of the eclipse above the earth's horizon, the power of the telescope used and the observer's personal equation. Similarly the apparent end of the eclipse follows the real emergence. Grandjean de Fouchy had long before tackled the problem and offered a partial solution in these terms:
Si cette partie visible était toujours de même grandeur, elle ne troublerait en rien le calcul, puisque ce ne serait qu'une quantité constante à ajouter au temps de l'emersion, et a soustraire au temps de l'immersion; mais cette moindre partie visible doit varier suivant l'intensité de la lumière des satellites... Cette intensité doit varier 1° en raison inverse des carrés de la distance de Jupiter au soleil, 2° en raison inverse des carrés de la distance de Jupiter à la terre.20
In order to construct tables of error for the eclipses of the satellites, Fouchy devised an ingenious system for determining for a given position the time by which the real eclipse lagged behind the apparent eclipse. Using two telescopes of equal power, he applied to the objective of one a diaphragm of such dimensions that the two apertures were in the same ratio as the greatest and shortest distances of Jupiter from the earth; the time lapse between the apparent eclipses observed with these two telescopes, he felt, should give the quantity of the equation for the invisible segment of the satellite. For forty years no further experiments were made, because, occupied with the secretariat of the Academy, Fouchy had neither the time nor the inclination to con- tinue them. And his discovery was not put to use, because although he had indicated a method for establishing an equation, he had not determined the quantity. Bailly says that he began to work on Fouchy's ideas as early as 1765.21 Unlike Fouchy, he used a single telescope for his observations. By means of a dia- phragm applied to the objective of the instrument, he diminished the aperture in the same ratio as Jupiter's greatest distance from the earth to its actual distance. When there was to be an eclipse of a satellite, he observed the moment of contact through the diminished aperture, then removed the diaphragm and timed the interval to the second or "true" contact. Such observations, conducted from 1768 on, enabled Bailly to confirm Fouchy's theory of the intensity of light, but showed no correlation between it and the equation of error for the eclipses.
Comme toutes ces formules supposent que l'on connaisse le diamètre des satellites et la grandeur du segment éclairé, qui devient insensible, il s'agissait de chercher les moyens de déterminer ces deux inconnues. J'ai pensé qu'on pouvait imiter, dans tous les moments, ce qui arrive dans les éclipses où la lumière diminue par degrés, et qu'en diminuant de même l'ouverture de la lunette, on parviendrait peut-être à faire disparaître le satellite.22
This eclipse-at-will was produced by a series of diaphragms of graduated size removed in rapid succession from the objective of the telescope. Bailly's first discovery as a result of this procedure was that the point of disappearance of the third satellite was at 1/64 its maximum intensity; for the other three, at 1/16; however he called the first satellite the largest and accounted for its lesser brilliance by its proximity to Jupiter.23
The measurement of the diameters of the satellites was in terms of their appearance from the center of Jupiter, and was determined by the time each takes to enter completely into Jupiter's shadow:
Ayant trouvé par l'observation le diaphragme qui fait disparaître le satellite, je connais le rapport du segment invisible au disque entier, au moment où le satellite disparaîtra; je couvre ensuite l'objectif de ma lunette d'un diaphragme un peu plus grand, qui me laisse apercevoir le satellite, mais faible et très petit, de manière que ce satellite cesse d'être visible dès que sa lumière sera tant soit peu diminuée. Je suis ainsi averti du moment où il commence à toucher l'ombre et l'intervalle de temps écoulé entre cet instant et celui de la véritable immersion me donne la mesure d'une grande partie du diamètre, d'où il est aisé de conclure le diamètre entier.24
Bailly supposed the area of the invisible portion of the satellite to be in inverse ratio to the square of the aperture, and he prepared a set of tables25 for computing the true diameter from the observed diameter. A by-product of this research was the discovery that the equation of error varied in conformity with Bouguer's tables of refraction,26 and Bailly computed his tables at two-degree intervals from the horizon to the zenith. It followed from Bailly's formula for the invisible portion of the satellite that, if the invisible segment had a fixed relation with the light-gathering power of a telescope, the relative errors of different telescopes could be precisely determined. With this idea in view, Bailly and Messier 27 together conducted a series of experiments with both refracting and reflecting telescopes. They further compared the results of their observations to determine the personal factor affecting their timing. Bailly concludes his mémoire with a number of suggestions for standard observing practice, designed to reduce errors of the instrument and of the observer. Although much of Bailly's work has been superseded and forgotten, there can be no doubt that it was extremely useful in its time. Bailly had not been able to make observations of the fourth satellite while working on this paper, and Lalande asked his permission to carry on his work in that field. Delambre and Maskelyne 28 continued the same line of investigation for a while, until it became apparent that basing the formula on the aperture of the diaphragm was not a sound procedure.29 We may note in passing that the summary of Bailly's long and painstaking paper which appeared in the history of the Academy for 1771 is unusually terse. The only word of praise is for Bailly's "recherches également ingénieuses et fines". The summary was written by Condorcet, who had officially become Secretaire Per- petuel in February 1773, when Fouchy went into re- tirement.30 The growing awareness of hostility in the Academy is apparent in Bailly's writings of this period. For one thing, he turned to a wider audience and, in due course, to a broader field of interest. Furthermore, he displays a new attitude of independence and self-justification bordering, in one case, on bitterness. Sometime during 1772, Bailly wrote a detailed letter to the Royal Society, outlining his methods for the study of the light of Jupiter's satellites. This letter was read before the Royal Society February 18 and 25, 1773, and published in the Philosophical Transactions for that year together with "Notes on the foregoing paper" by the Reverend Samuel Horsley,32 who, expressing certain reservations on matters of detail, nevertheless voices the highest opinion of Bailly's work.
- 18 MEM AC SCI 1771: 580-667.
- 19 Eloge, 323.
- 20 MEM AC SCI 1732: 42
- 21 MEM AC SCI 1771: 581.
- 22 Ibid., 588.
- 23 This is in accord with Galileo's findings, but contrary to modern knowledge, which makes the third and fourth satellites of approximately equal size and larger than the first and second.
- 24 MEM AC SCI 1771: 615.
- 25 Ibid., 612-613. 26 Pierre Bouguer (1698-1758), Traite de la gradation de la lumiere, Paris, 1760.
- 27 Charles Messier (1730-1817), astronomer and fellow-academician.
- 28 Nevil Maskelyne (1732-1811), F. R. S., Astronomer Royal.
- 29 Delambre, Histoire de I'astronomie au 186 sie'cle, 745 ff.
- 30 The volume for 1771 was published in 1774.
Elogi
Gli elogi testimoniano lo sviluppo del pensiero di Bailly. Tratto tipico della sua epoca, Bailly è meno interessato alla forma estetica che nello scopo didattico dell'arte. Convinto della superiorità della sua epoca illuminata, Bailly è anche affascinato dal concetto di "uomo naturale", con il quale si intende non l'uomo primitivo, ma il denominatore comune degli uomini in tutte le società in tutti i periodi. Storia, diritto, arte, e scienza sono tutti visti come espressioni del progresso fisico e morale dell'uomo.
La composizione dell′Éloge de Leibnitz in particolare avrebbe avuto un effetto profondo e duraturo sul pensiero di Bailly. Anche se dà voce al credo del philosophe, dell'uomo universale, è stato il système ad averlo attratto, la «verosimigianza sostituita alla verità inaccessibile». Al periodo di questi éloges si potrebbe datare anche la germinazione di numerose idee di Bailly che trovarono la luce nelle opere successive, come l′Histoire de l'astronomie ancienne, le Lettres sur l'Atlantide de Platon e l′Essai sur les fables et sur leur histoire.
Bailly godette di un moderato successo con i suoi éloges. Dei quattro presentati nelle varie competizioni, uno solo vinse il prix d'eloquence, mentre altri due hanno ricevuto una menzione d'onore. Anche se quelli di Carlo V, Molière e Lacaille non sembra fossero andati immediatamente in stampa, gli altri due, quello su Corneille e quello su Leibniz, furono invece pubblicati ognuno per due edizioni. Nel 1770 fu inoltre pubblicata a Berlino e a Parigi da Delalain un'ulteriore edizione che raccoglieva tutti e cinque gli éloges. Eppure, se Bailly era alla ricerca di fama e fortuna con questo tipo di scrittura, si deve comunque ammettere che non colse nel segno. Se il suo obiettivo era quello di ottenere la segreteria dell'Accademia francese delle scienze, come gli era stato promesso da D'Alembert che poi però lo aveva tradito preferendogli Condorcet, non ci riuscì. Alcuni aneddoti, riportati dal biografo di Bailly, Michel de Cubières, sembrano infatti riflettere anche una certa disillusione da parte dell'insigne astronomo sia nei confronti degli éloges sia verso il mondo accademico più in generale.[5] A quanto pare, infatti, Bailly arrivò a dire che «i premi accademici non provano nulla» e che la maggior parte degli éloges non erano altro che «folies de jeuness» ovvero "follie di gioventù".[5]
Bailly philosophe
da pag 43
About the time of Bailly's retirement to Chaillot, we can detect a change in his thinking which was, for a time, to widen the gap between him and the philo- sophes. Bailly seems always to have needed a guide and mentor-first Lacaille, then Clairaut, d'Alembert, and Buffon. The first two directed his efforts in the fields of astronomy and mathematics; d'Alembert and Buffon enocuraged him in the literary field. When he turned to the popularization of astronomy, he came under the influence of Court de Gebelin 51 whose nine volume Monde primitif was just appearing. This work was an attempt to reduce the complexities of civilization, its customs, traditions, speech, etc. to a universal theme. Court de Gebelin felt that the key to the mysteries of nature was to be found in the history of antiquity and that history, properly understood, might lead humanity to a new golden age. His vision of le grand ordre was utopian, and much of his history is inaccurate; but in many ways Court de Gebelin was a precursor of modern thinkers. His theory of fables as allegorical documents foreshadows the work of modern folklorists. Similarly his search for the primitive language which was the source of all languages anticipated the linguistic research of the nineteenth century. If Bailly had acquired from his astronomical research a conviction that truth was basically simple, he had also learned from Leibnitz to substitute "vraisemblance" for "la verite inaccessible." The influence of Court de Ge'belin was to encourage this speculative bent and cause Bailly to be branded "frere illumine" by the more ardent philosophes. Yet the illuminism of Bailly's work, if it can be called that, is not so far removed from the rationalism of his detractors, but is rather symptomatic of the deterioration of systematic doubt which was common towards the end of the century.
Il metodo epistemologico di Bailly
«Il dubbio è sempre consentito nella scienza, è la pietra di paragone della verità. Tuttavia il dubbio deve avere dei limiti; non tutte le verità possono essere dimostrate come verità matematiche. Il genere umano avrebbe troppo da perdere se riducesse tutto a questa singola classe. Le testimonianze equilibrate, le probabilità ponderate, le storie raffrontate e chiarite le une con le altre, formano attraverso la loro unione una luce forte che può portare all'evidenza. E quando la filosofia con questi aiuti arriva a dei risultati fondati sulla natura delle cose e degli uomini, vi è ragione di credere e non di dubitare.»
Bailly scrisse, in una lettera a Voltaire, che il dubbio metodologico, deve avere dei limiti, e tutta la ricerca gnoseologico-epistemologica non può ridursi in puro esercizio di scetticismo in quanto non tutte le verità possono essere dimostrate come verità matematiche. Secondo lui, ci sono tre criteri utili per congetturare ipotesi plausibili in qualunque campo della conoscenza:
- le testimonianze equilibrate;
- le probabilità ponderate;
- le storie raffrontate e chiarite le une con le altre.
Questi tre criteri, secondo Bailly, sono una sorta di base di vraisemblance (ovvero la verosimiglianza). Un'ipotesi epistemologica generata a partire da questi criteri, infatti, pur non essendo spesso verificabile matematicamente è comunque, secondo Bailly, "verosimile", ed possiede una certa dignità gnoseologica. Come infatti lui stesso afferma, tali crtieri: «Formano attraverso la loro unione una luce forte che può portare all'evidenza».
Apparentemente, questo approccio appare plausibile e ragionevole nelle scienze non esatte come la paleoastronomia e la filologia comparata, di cui Bailly si occupava. L'astronomo Elio Antonello scrive a proposito di ciò: «Secondo me, ci sono dei problemi cruciali simili nei campi dell'astronomia culturale e nell'archeoastronomia. In particolare, il problema dell'intenzionalità delle orientazioni astronomiche degli antichi edifici: quando è possibile concludere che tale intenzionalità è evidente? C'è per caso una dimostrazione rigorosa?»
L'astrofisico Bradley Schaefer, nel 2006, aveva proposto quattro criteri ragionevoli e plausibili sull'onda di ciò che aveva detto Bailly. L'obiettivo di Schaefer era quello di rispondere proprio alla domanda fondamentale se si è in grado di dimostrare che gli allineamenti scoperti sono stati intenzionalmente costruiti nelle strutture:
- la significatività statistica degli allineamenti;
- le informazioni archeologiche che potrebbero portare all'intenzione;
- l'evidenza etnografica riguardante i desideri e le conoscenze dei costruttori;
- il caso astronomico per l'utilità degli allineamenti annunciati.
Verificando tali criteri era possibile secondo Schaefer stabilire l'intenzionalità degli allineamenti, che in questo modo secondo lui poteva essere dimostrata. Senza la prova dell'intenzionalità, infatti tutto quello che si avrebbe avuto sarebbe stato, citando Antonello, «un divertente mito urbano».
Secondo Antonello esiste una sorta di analogia tra i criteri generali di Bailly e quelli di Schaefer. Ad esempio infatti le proposizioni 2 e 4 possono essere messe in relazione con le «testimonianze equilibrate» di cui parlava Bailly, la proposizione1 con le «probabilità ponderate», mentre la 3 con le «storie raffrontate e chiarite le une con le altre».
Antonello afferma che come quelli di Bailly si potrebbe dire che i quattro criteri di Schaefer «formano attraverso la loro unione una luce forte che può portare all'evidenza»; eppure bisogna chiarificare il significato della parola "evidenza". Questa parola va giudicata rispetto all'asserzione di Bailly secondo cui: «non tutte le verità possono essere dimostrate come verità matematiche». Il senso della frase è chiaro: spesso, quando si ricerca la "verità" nelle scienze non esatte è lecito attendersi che non tutto possa dimostrarsi a partire da principi primi, ma attraverso l′empiria stessa, attraverso cioè una estensione del metodo galileiano che però permette di concludere solo sulla verosimiglianza delle ipotesi (quantificando quanto esse siano d'accordo con le evidenze sperimentali) e non sull'effettiva "verità" delle stesse.
Anche le espressioni "molto probabile" o "probabile" spesso usate dagli archeoastronomi o in generale da chi si occupa di scienze non esatte (Bailly preferirebbe dire "verosimile"), secondo Antonello «devono essere usate con molta cura, a meno che non sono supportate da metodi archeologici». Quali sono quindi le prove, le dimostrazioni e le evidenze nei campi delle scienze non esatte? Secondo lo stesso Antonello, «non c'è ancora una chiara risposta». L'antropologo Anthony Aveni (nel 2006) cercò di discutere in particolare il problema delle prove dell'intenzionalità, sottolineando i limiti e i possibili difetti dell'approccio di Schaefer (e dunque quello dello stesso Bailly), considerato da un punto di vista antropologico ed etnologico. In particolare, egli osservava che gli strumenti e i metodi delle scienze fisiche, non possono essere adattati alle scienze umane che, per loro stessa natura, non sono esatte. L'astronomo e archeologo Clive Ruggles (nel 2011), tuttavia, criticò una dichiarazione così forte, ricordando ad esempio che il «metodo scientifico aderiva alla perfezione agli studi sulla pittura rupestre». D'altra parte, Ruggles concluse che «identificare metodi affidabili per ponderare insieme i diversi tipi di dati che l'astronomo culturale è costretto ad affrontare in diverse situazioni, in modo da dedurre l'interpretazione "migliore", rimane contemporaneamente il più impegnativo e più opprimente problema di fronte alla nostra "interdisciplina" in futuro».
L'importanza della vraisemblance
Note
- ^ Jean Sylvain Bailly, Lettres sur l'Atlantide de Platon.
- ^ Lettre de l'auteur du Monde primitif a messieurs ses souscripteurs sur le magnétisme animal, 42, Parigi, Valleyre, 1784.
- ^ Fête de la Fédération su cosmovisions.com
- ^ 14 luglio 1790: la Festa della Federazione di Giovanni Ligasacchi
- ^ a b Michel de Cubières, Recueil des pièces intéressantes sur les arts, les sciences et la littérature, ouvrage posthume de Sylvain Bailly, précédé de la vie littéraire et politique de cet homme illustre, 1810, XX-XXII.
- ^ Bailly, Lettres sur l'Atlantide de Platon et sur l'ancienne histoire de l'Asie , 1779; pp. 6-7, nota ad una lettera di Voltaire