Not until 1733 was the first really scientific investigation of the parallel postulate printed. Tat year the Italian Jesuit priest Girolamo Seccheri (1667-1733) while professor of Mathematics at the University of Pavia,received permission to print a little book entitled Euclides ab omni naevo vindicatus (Euclild freed of Every Flaw). In an earlier work on logic, Saccheri had become chamed with the powerful method of reductio an absurdum and conceived the idea of applying this method to an investigation of the parallel