first edition of galileo's statement and defence of the copernaican heliocentric system

As with his later Discorsi (1638), Dialogo is presented as a series of dialogues between three characters, Salviati, Sagredo and Simplicio, taking place over a span of four days. Salviati argues for the Copernican system and represents Galileo's views directly, through referring to him as 'Academician', whilst Simplicio adopts the geocentric, Aristotelian stance; Sagredo's role is that of the layman, initially taking the middle-ground. The discussion doesn't just revolve around the celestial heavens, but also touches on the other contemporary sciences of the day, including William Gilbert's work on magnetism.

The Dialogue was published under a formal license from the Inquisition, but in 1633 Galileo was tried for heresy. Urban VIII, who had Galileo arrested and had this work placed on the Index Liborum Prohibitorum (Index of Prohibited Books), thought he was the basis for the character of Simplicio. In an undeclared action the publication of anything else Galileo had written or ever might write was also banned. This ban alienated Galileo from the Jesuits, who had supported him up until this point. He was tried by the Inquisition, found 'vehemently suspect of heresy', forced to recant, and spent the rest of his life under house arrest. It was while Galileo was under house arrest that he wrote one of his finest works, Discorsi. Here he summarised the work he had done some forty years earlier, on the two sciences now called kinematics and strength of materials.

First edition, large 8vo, woodcut printer's device on title-page, woodcut initials and headpieces, printed correction slip pasted to marginalia verso of F6 as usual, lacking frontispiece, without final blank leaf, occasional damp-staining or browning, later endpapers, early 19th century painted vellum, red and green leather spine labels with gilt lettering, edges speckled to a chevron pattern, housed in custom burgundy buckram folding box.

Horblit 18c; PMM 128; Riccardi I 511; Norman 858; Wellcome 2647a