The Praeparatio consists of fifteen books completely preserved. Eusebius considered it an introduction to Christianity for pagans, but its value for many later readers is more because Eusebius included information from historians and philosophers not preserved elsewhere. Much of what Eusebius reports about philosophy he copied from the works of the Peripatetic philosopher Aristocles of Messene. Among the most important of these otherwise lost works are:
Excerpts from Timon of Phlius' book Python including what is known as the Aristocles Passage in which Pyrrho summarizes his new philosophy of Pyrrhonism, and which represents a translation of the Buddhistthree marks of existence into ancient Greek.
A summary of the writings of the Phoenician priest Sanchuniathon; its accuracy has been shown by the mythological accounts found on the Ugaritic tables.
The account of Euhemerus's wondrous voyage to the island of Panchaea, where Euhemerus purports to have found his true history of the gods, which was taken from Diodorus Siculus's sixth book.
Excerpts from the writings of the Platonist philosopher Atticus.
Excerpts from the Book of the Laws of the Countries by the early Christian author Bardaisan of Edessa, the Syriac original of which was not discovered until the 19th century.
The term also denotes an early church doctrine, praeparatio evangelica, meaning a preparation of the gospel among culturesyet to hear of the message of Christ. " argued that God had already sowed the older cultures with ideas and themes that would grow to fruition once they were interpreted in a fully Christian context." Eusebius' own Praeparatio Evangelica does not adopt the common notion of Greek philosophy as a "preparation for the Gospel." Eusebius instead offers a lengthy argument for the wisdom of the ancient Hebrews becoming a preparation for Greek philosophy. For Eusebius, the Greeks stole any truths they possessed from the more ancient Hebrews.
