Dialogo. Dove ne i congressi di quattro giornate si discorre sopra i due massimi sistemi del mondo Tolemaico, e Copernicano.

Florence: Giovanni Batista Landini, 1632.

First edition of this epoch-making work, Galileo’s celebrated defence of the Copernican view of the solar system, the most notorious banned book of the 17th century. Written in dialogue form, it “was designed both as an appeal to the great public and as an escape from silence … it is a masterly polemic for the new science. It displays all the great discoveries in the heavens which the ancients had ignored; it inveighs against the sterility, wilfulness, and ignorance of those who defend their systems; it revels in the simplicity of Copernican thought and, above all, it teaches that the movement of the earth makes sense in philosophy, that is, in physics … The Dialogo, more than any other work, made the heliocentric system a commonplace” (PMM). “The Dialogo, far more than any work, convinced men of the truth of the Copernican system” (Gingerich). Pope Urban VIII was not persuaded, however, and immediately convened a special commission to examine the book and make recommendations. In casting the Pope as the simple-minded Aristotelian Simplicius, Galileo brought upon himself arrest, trial by the Inquisition and life imprisonment. The sentence was commuted to permanent house arrest, while the printing of any of his works was forbidden. The Dialogo remained on the index until 1832.

In August 1597, Galileo wrote to Kepler expressing his sympathies for Copernicanism, having received a copy of the Mysterium cosmographicum (1596) from him. At this time Galileo’s support for Copernicus was Earth-based: Galileo had devised a theory of the tides involving the combined rotational motions of the Earth around its axis and, after Copernicus, around the Sun. Everything changed early in 1610 when Galileo first turned a telescope to the skies. Not only was the moon revealed to be mountainous and the Milky Way to consist of separate stars, contrary to Aristotelian principles, but a host of new fixed stars and four satellites of Jupiter were promptly discovered. Galileo’s account of these discoveries was published in the Sidereus nuncius (Venice, 1610). Galileo saw in the satellites of Jupiter a miniature planetary system in which, as in Copernican astronomy, it could no longer be held that all moving heavenly bodies revolved exclusively about the earth. Galileo first spoke out decisively in print for the Copernican hypothesis in his 1613 work on sunspots, Istoria e dimostrazioni intorno alle macchie solari. During its composition he had taken pains to determine the theological status of the idea of incorruptibility of the heavens, finding that this was regarded by churchmen as an Aristotelian rather than a Catholic dogma. But attacks against Galileo and his followers soon appeared in ecclesiastical quarters. These came to a head with a denunciation from the pulpit in Florence late in 1614. A year later Galileo went to Rome (against the advice of his friends and the Tuscan ambassador) to clear his own name and to prevent, if possible, the official suppression of the teaching of Copernicanism. In the first, he succeeded, but on the second he failed: Galileo was instructed on 26 February 1616 to abandon the holding or defending of that view. No action was taken against him, nor were any of his books suspended. Returning to Florence, Galileo took up less theologically controversial topics, culminating in the publication of Il Saggiatore in 1623. Just before it emerged from the press, Maffeo Barberini became pope as Urban VIII. Galileo journeyed to Rome in 1624 to pay his respects to Urban, and secured from him permission to discuss the Copernican system in a book, provided that the arguments for the Ptolemaic view were given an equal and impartial discussion. Urban refused to rescind the edict of 1616, although he remarked that had it been up to him, the edict would not have been adopted.

“The Dialogue Concerning the Two Chief World Systems occupied Galileo for the next six years. It has the literary form of a discussion between a spokesman for Copernicus, one for Ptolemy and Aristotle, and an educated layman for whose support the other two strive. Galileo thus remains technically uncommitted except in a preface which ostensibly supports the anti-Copernican edict of 1616. The book will prove, he says, that the edict did not reflect any ignorance in Italy of the strength of pro-Copernican arguments. The contrary is the case; Galileo will add Copernican arguments of his own invention, and thus he will show that not ignorance of or antagonism to science, but concern for spiritual welfare alone, guided the Church in its decision.

“The opening section of the Dialogue critically examines the Aristotelian cosmology. Only those things in it are rejected that would conflict with the motion of the earth and stability of the sun or that would sharply distinguish celestial from terrestrial material and motions. Thus the idea that the universe has a center, or that the earth is located in such a center, is rejected, as is the idea that the motion of heavy bodies is directed to the center of the universe rather than to that of the earth. On the other hand, the Aristotelian concept of celestial motions as naturally circular is not rejected; instead, Galileo argues that natural circular motions apply equally to terrestrial and celestial objects. This position appears to conflict with statements in later sections of the book concerning terrestrial physics. But uniform motion in precise circular orbits also conflicts with actual observations of planetary motions, whatever center is chosen for all orbits. Actual planetary motions had not been made literally homocentric by any influential astronomer since the time of Aristotle. Galileo is no exception; in a later section he remarked on the irregularities that still remained to be explained. Opinion today is divided; some hold that the opening arguments of the Dialogue should be taken as representative of Galileo’s deepest physical and philosophical convictions, while others view them as mere stratagems to reduce orthodox Aristotelian opposition to the earth’s motion.

“Important in the Dialogue are the concepts of relativity of motion and conservation of motion, both angular and inertial, introduced to reconcile terrestrial physics with large motions of the earth, in answer to the standard arguments of Ptolemy and those added by Tycho Brahe. The law of falling bodies and the composition of motions are likewise utilized. Corrections concerning the visual sizes and the probable distances and positions of fixed stars are discussed. A program for the detection of parallactic displacements among fixed stars is outlined, and the phases of Venus are adduced to account for the failure of that planet to exhibit great differences in size to the naked eye at perigee and apogee. Kepler’s modification of the circular Copernican orbits is not mentioned; indeed, the Copernican system is presented as more regular and simpler than Copernicus himself had made it. Technical astronomy is discussed with respect only to observational problems, not to planetary theory.

“To the refutation of conventional physical objections against terrestrial motion, Galileo added two arguments in its favor. One concerned the annual variations in the paths of sunspots, which could not be dynamically reconciled with an absolutely stationary earth. Geometrically, all rotations and revolutions could be assigned to the sun, but their conservation would require very complicated forces. The Copernican distribution of one rotation to the sun and one rotation and one revolution to the earth fitted a very simple dynamics. The second new argument concerned the existence of ocean tides, which Galileo declared, quite correctly, to be incapable of any physical explanation without a motion of the earth. His own explanation happened to be incorrect; he argued that the earth’s double motion of rotation and revolution caused a daily maximum and minimum velocity, and a continual change of speed, at every point on the earth. The continual variation of speed of sea basins imparted different speeds to their contained waters. The water, free to move within the basins, underwent periodic disturbances of level, greatest at their coasts; the period depended on sizes of basins, their east-west orientations, depths, and extraneous factors such as prevailing winds. In order to account for monthly and annual variations in the tides, Galileo invoked an uneven speed of the earth-moon system through the ecliptic during each month, caused by the moon’s motion with respect to the earth-sun vector; for annual seasonal effects, he noted changes of the composition of rotational and revolutional components in the basic disturbing cause.

“The Dialogue was completed early in 1630. Galileo took it to Rome, where it was intended to be published by the Lincean Academy. There he sought to secure a license for its printing. This was not immediately granted, and he returned to Florence without it. While the matter was still pending, Federico Cesi died, depriving the Academy of both effective leadership and funds. Castelli wrote to Galileo, intimating that for other reasons he would never get the Roman imprimatur and advising him to print the book at Florence without delay. Negotiations ensued for permission to print the book at Florence. Ultimately these were successful, and the Dialogue appeared at Florence in March 1632. A few copies were sent to Rome, and for a time no disturbance ensued. Then, quite suddenly, the printer was ordered to halt further sales, and Galileo was instructed to come to Rome and present himself to the Inquisition during the month of October …

“Confined to bed by serious illness, he at first refused to go to Rome. The grand duke and his Roman ambassador intervened stoutly in his behalf, but the pope was adamant. Despite medical certificates that travel in the winter might be fatal, Galileo was threatened with forcible removal in chains unless he capitulated. The grand duke, feeling that no more could be done, provided a litter for the journey, and Galileo was taken to Rome in February 1633.

“The outcome of the trial, which began in April, was inevitable. Although Galileo was able to produce an affidavit of Cardinal Bellarmine to the effect that he had been instructed only according to the general edict that governed all Catholics, he was persuaded in an extrajudicial procedure to acknowledge that in the Dialogue he had gone too far in his arguments for Copernicus. On the basis of that admission, his Dialogue was put on the Index, and Galileo was sentenced to life imprisonment after abjuring the Copernican “heresy.” The terms of imprisonment were immediately commuted to permanent house arrest under surveillance. He was at first sent to Siena, under the charge of its archbishop, Ascanio Piccolomini. Piccolomini, who is said to have been Galileo’s former pupil, was very friendly to him. Within a few weeks he had revived Galileo’s spirits—so crushed by the sentence that his life had been feared for—and induced him to take up once more his old work in mechanics and bring it to a conclusion. While at Siena, Galileo began the task of putting his lifelong achievements in physics into dialogue form, using the same interlocutors as in the Dialogue” (DSB).

Copies of this book in contemporary bindings are relatively uncommon, most copies appearing on the market being in 18th century, or later, bindings. After the prohibition of the Dialogo in 1633, the book could not be legally sold in Italy. Since there is no documentary record of copies being systematically destroyed, unsold copies may have been withheld from the market. These copies would probably have been released early in the 18th century, when secular Florentine political authorities took a decisive and quite aggressive stance against the Church relating to Galileo (a second edition of the Dialogo was published at Florence in 1710, and the second edition of the Opera appeared there in 1718). This may explain why so many copies of the Dialogo are found in 18th century bindings. In particular, and somewhat unusually for a 17th-century book, copies of the Dialogo are quite often found uncut in 18th century wrappers, suggesting that these copies remained unbound until the 18th century.



4to, pp. [8], 458, [16], including errata leaf and frontispiece signed Stefano della Bella, showing Aristotle, Ptolemy and Copernicus in disputation. Printed correction slip in margin of F6v (= p. 92). Contemporary vellum with later black leather lettering-piece on spine.

Item #4377

Price: $125,000.00

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