Expositor's Bible Commentary Commentary Luke 1:4

"that thou mightest know the certainty concerning the things wherein thou wast instructed." — Luke 1:4 (ASV)

Though it is not clear whether Theophilus was a believer, he had doubtless received some instructions in the faith. He had learned of both the words and the deeds of Jesus. “Taught” (GK 2994) may refer to formal church teaching (Galatians 6:6), but not necessarily. For some reason Theophilus needed assurance as to the truth of the things taught him. Possibly he was troubled by denials of the Resurrection and other historical foundations of the faith that incipient Gnostic speculation was challenging.