The scroll, originally several yards of papyrus rolled around two wooden runners, was found half burnt in 1962. It dates to around 340 B.C., during the reign of Philip II of Macedon, father of Alexander the Great.
"It is the oldest surviving book, if you can use that word for a scroll, in western tradition," Veleni said. "This was a unique find, of exceptional importance."
Greek philosophy expert Apostolos Pierris said the text may be a century older.
"It was probably written by somebody from the circle of the philosopher Anaxagoras, in the second half of the 5th century B.C.," he said.
Anaxagoras, who lived in ancient Athens, is thought to have been the teacher of Socrates and was accused by his contemporaries of atheism.