Giovanni Girolamo Saccheri

Giovanni Girolamo Saccheri, who lived from 1667 to 1733, was an Italian Jesuit priest, scholastic philosopher and mathematician, considered the forerunner of non-Euclidean geometry. The son of a lawyer, born in Sanremo, he showed early precocity, entered the Jesuit novitiate in 1685 and studied at the Jesuit College of Brera in Milan, where Tommaso Ceva introduced him to his brother Giovanni, who became his mentor in mathematics. He was ordained in 1694, taught philosophy at the University of Turin until 1697 and then philosophy, theology and mathematics at the University of Pavia until his death. His Logica demonstrativa earned him a place in the history of modern logic. His last book, Euclides ab omni naevo vindicatus, tried to prove Euclid's parallel postulate by contradiction and unwittingly derived results of hyperbolic geometry, until Eugenio Beltrami rediscovered it in the nineteenth century.