In christopher marlowe's the tragical history of doctor faustus, why did faustus begin to believe that human salvation was impossible?

In Christopher Marlowe's "The Tragical History of Doctor Faustus", Faustus begin to believe that human salvation became impossible is because of the fact that he believed in Predestination. It's a theory wherein humans are already fated ever since they are born, and due to the evil in the world, he deemed that it's actually impossible to save humankind.