Thank you for the question on the purpose of the Gospel of Luke, “Why did Luke write his Gospel?”
In the introduction of the Gospel of Luke, the author states the reason why he writes this letter to him. He wanted Theophilus to be assured of the things that he had heard is true. Luke declares that he has done a careful search and this is his report to him.
Luke 1 says this: “Many have undertaken to draw up an account of the things that have been fulfilled[a] among us, 2 just as they were handed down to us by those who from the first were eyewitnesses and servants of the word. 3 With this in mind, since I myself have carefully investigated everything from the beginning, I too decided to write an orderly account for you, most excellent Theophilus, 4 so that you may know the certainty of the things you have been taught.”
Here are some additional thoughts on the writing of this letter:
A. The Gospel of Luke was intended for one person, Theophilus.
This letter was not addressed to a church or to a group of people. It was written to a person who had some status within the Roman government.
B. The Gospel of Luke was written to a believer.
It appears that this Roman official became a believer. Perhaps through Paul’s missionary journey or the testimony of other believers, he came to a place of faith in Jesus. He may have had a lot of questions. He may have had bits and pieces of testimony or recounting by others.
Did Theophilus asked Luke to give him an account or did Luke wanted him to have a clearer picture of Jesus? It appeared that at least Luke wanted this Roman official to have a fuller account of the life of Jesus.
C. The Gospel of Luke was a personal accounting of the life of Jesus.
Luke declares that he did a careful investigation from the beginning. It doesn’t appear that he just copy second hand information, but that he went to Israel to hear or interview witnesses. The record is his findings of the facts.
I don’t imagine that Luke would fabricate the life of Jesus or add false testimony. If the things that were taught to Theophilus was incorrect, he would have said something.
Modern scholars say that why isn’t the lineage that he recorded the same as Matthew’s account. Isn’t that a contradiction? It appears that by the time Luke investigated the beginning of Jesus that Joseph had died earlier. All he had was Mary’s recounting of her lineage and her story.
D. The Gospel of Luke is an orderly unfolding of the life of Jesus.
The Gospel of Matthew is written based on themes while the Gospel of Luke is historical unfolding of the life of Jesus. His writing is more of a time line of the life of Jesus and the events that happened in that time line.
The text doesn’t state when or how he sent this letter to Theophilus. The record of this document would affirm that Theophilus kept that letter and at some point in time it was read to others or copied by others so that this Gospel is preserved.
SUMMARY: Theophilus wanted to know the time line of Jesus’ life and his words and works. The Gospel of Luke provided Theophilus a written document that Luke gave or sent to him.