 Grassi 's arguments and conclusions were criticised in a subsequent article , Discourse on the Comets , published under the name of one of Galileo 's disciples , a Florentine lawyer named Mario Guiducci , although it had been largely written by Galileo himself . Galileo and Guiducci offered no definitive theory of their own on the nature of comets although they did present some tentative conjectures that are now known to be mistaken . In its opening passage , Galileo and Guiducci 's Discourse gratuitously insulted the Jesuit Christopher Scheiner , and various uncomplimentary remarks about the professors of the Collegio Romano were scattered throughout the work . The Jesuits were offended , and Grassi soon replied with a polemical tract of his own , The Astronomical and Philosophical Balance , under the pseudonym Lothario Sarsio Sigensano , purporting to be one of his own pupils . 
