This title includes an introduction by Antonio Favaro. Italian astronomer and philosopher GALILEO GALILEI (1564-1642) is unquestionably one of the most influential forces upon the modern understanding of the physical world. But even few armchair scientists have discovered his writing in his own words. This is Galileo's final work, and the most mature explication of his scientific philosophies. Presented as a dialogue among three imaginary men who represent Galileo himself at different stages of his thought processes, it explores the two sciences, at their most basic, Galileo pioneered: engineering and the laws of motion, the latter of which anticipates Isaac Newton by half a century. This classic 1914 translation is by American physicist HENRY CREW (1859-1953) and Italian scholar of the Italian language ALFONSO DE SALVIO (1873-1938), both of whom were serving on the faculty of Northwestern University when they produced his work. Galileo himself could not publish this 1638 work throughout much of Europe after his conviction by the Inquisition, but this volume makes him readily accessible to lay scientists today.