Since many have undertaken to set in order a narrative concerning those matters which have been fulfilled among us,
That thou mightest know the certainty concerning the things wherein thou wast instructed ... The Greek word here rendered "things" is actually "words" (English Revised Version (1885) margin); and the last clause means "which thou wast taught by word of mouth," unmistakable references to the oral instruction received by Christians in those times, prior to and after their acceptance of the faith.  This makes the implications of this passage to be of epic proportions.  Despite the fact of there having been "many" written portions of the gospel message, even so important a person as Theophilus had received only word-of-mouth teaching, indicating the universality of the word-of-mouth method of instruction.  This fully accounts for the word-by-word correspondence to be found in certain episodes recorded in the synoptic Gospels, all of them written independently.  Luke's Gospel was written for the precise purpose of confirming the accuracy of the oral instruction Theophilus had already received.  The glimpse afforded here, as Dummelow said, "is all that is really known, as distinguished from what is guessed about the sources of the synoptic Gospels."[6]