Poggio Bracciolini a 15th-century papal emissary and obsessive book hunter, saved the last copy of the Roman poet Lucretius's On the Nature of Things from near-terminal neglect in a German monastery, thus reintroducing important ideas that sparked the modern age. This event is vividly described by the renaissance scholar Stephen Greenblatt in The Swerve. He sees it as the origin of the renaissance and, in effect, of modernity.
Lucretius
Lucretius was a passionate follower of the Greek philosopher Epicurus. He believed that the gods did not concern themselves with mortal affairs and did not create the universe, which was composed of minuscule particles. Lucretius describes an entirely god-free origin of life, in which living creatures simply heave themselves from the earth, not through the actions of a creator, but as a result of the vital forces of the universe.
Epicureanism
It was in fact an austere philosophy in which "pleasure" meant freedom from pain and fear rather than self-indulgence, epicureanism became identified among most Christian writers with swinish self-indulgence. The story told by the book is that epicureanism flourished at Rome, was lost, and then was suddenly rediscovered and transformed the world.
Atoms
Lucretius believed that the gods did not create the universe, which was composed of minuscule particles. These atoms move perpetually and randomly through a void. As they do so they "swerve" from a direct course, and may strike against each other.