George Leo Haydock, on Luke 1:3

Having diligently obtained. Here we see, that although the Holy Ghost regulated the pen of the holy writers, that they might not err; they still employed human means to search and find out the truth of things they mentioned. Even so do general councils, and the president thereof, the holy pontiff, discuss and examine all causes by human means, although they have the promise from Jesus Christ of the aid, assistance, and direction of his holy Spirit; (St. John xvi. 13,) as is manifest from the very first council of the apostles, held at Jerusalem. (Acts xv. 7. and 28.) — Most excellent Theophilus. This word, Theophilus, by its etymology, signifies a lover of God: but here we may rather understand some particular person, by the title given him of most excellent, or best: which, at that time, was given to persons in dignity; as to to Felix, Acts xxiii. 26. and to Festus, Acts xxvi. 25. (Witham) — Kratiste , may signify most powerful from Kratos , strength, or Kratein , to conquer; or, as most generally given, from Kreitton . — Theophilos , may be interpreted either a lover of God, or one beloved of God. Whoever, therefore, loves God, and desires to be beloved by Him, should consider this gospel as penned for himself, and should preserve it as a pledge deposited in his hands. (Ven. Bede)