Luke 1:4
so that you may know the certainty of the things you have been taught.
What it says
He writes so that Theophilus may know the certainty of the teaching he has received.
What it is doing
It states the purpose: certainty for the instructed reader.
In context
1Many have undertaken to compose an account of the things that have been fulfilled among us, 2just as they were handed down to us by the initial eyewitnesses and servants of the word. 3Therefore, having carefully investigated everything from the beginning, it seemed good also to me to write an orderly account for you, most excellent Theophilus, 4so that you may know the certainty of the things you have been taught.