 In 1619 , Galileo became embroiled in a controversy with Father Orazio Grassi , professor of mathematics at the Jesuit Collegio Romano . It began as a dispute over the nature of comets , but by the time Galileo had published The Assayer ( Il Saggiatore ) in 1623 , his last salvo in the dispute , it had become a much wider controversy over the very nature of science itself . The title page of the book describes Galileo as philosopher and " Matematico Primario " of the Grand Duke of Tuscany . 
