One of the most celebrated polemics in the history of science, this work arose from the controversy between Galileo and the Jesuit Orazio Grassi over the three comets of 1618. Grassi had published a work under the pseudonym of Lothario Sarsi in 1619, which attacked Galileo's arguments, and Galileo in his reply expounded his most important ideas on the philosophy of scientific investigation. He "distinguished physical properties of objects from their sensory effects, repudiated authority in any matter that was subject to direct investigation, and remarked that the book of nature, being written in mathematical characters, could be deciphered only by those who knew mathematics" (DSB).