The conversationists in Galileo’s Dialogue include a scholar of Copernicus, a man called Salviati, who makes a presentation of Galileo’s own scientific views, calling him a respected academician, and an Aristotelian scholar called Simplicio who presents the arguments for the Aristotelian and Ptolemaic view of the universe. Galileo’s contempt for Aristotle becomes clear from the name that he has given to the Aristotelian scholar—“Simplicio” means simpleton. Galileo thought that the Aristotelians were a bunch of simpletons or fools.
The Dialogue of more than 600 pages is a direct confrontation between Galileo and Aristotle—the arguments that Simplicio presents are demolished one by one by Salviati who presents a series of evidence in the form of scientific graphs, mathematical equations, and information derived from the direct observations through the telescope. They discuss the movement of heavenly bodies; the craters and mountains on the moon; the phases of Venus; the relation between ocean tides and motion of the earth; and much else. In the end, Galileo (through Salviati) manages to establish that while Copernicus was right on most things, Aristotle (and Ptolemy) had an erroneous view of the universe.
The book became influential during the Renaissance; its first edition was sold out immediately after publication. But it alienated Galileo from the religious establishment. The Dialogue was placed in the list of forbidden books and on October 1, 1632, Galileo was summoned before the Inquisition to face prosecution for trying to defame the religious order.