These are excellent questions and I thank you for submitting them. Let’s read Luke’s introduction in Luke 1:1-4: “Inasmuch as many have undertaken to compile an account of the things accomplished among us, just as they were handed down to us by those who from the beginning were eyewitnesses and servants of the word, it seemed fitting for me as well, having investigated everything carefully from the beginning, to write it out for you in consecutive order, most excellent Theophilus; so that you may know the exact truth about the things you have been taught” (NASB).

1. Luke’s RELIABILITY and SOURCE MATERIAL. We see from these verses that Luke was a TRUE HISTORIAN whose goal was to be ACCURATE. His research was done carefully, methodically, and thoroughly for he tells us that the things he was about to write were “handed down to us by those who from the beginning were eyewitnesses and servants of the word” (verse 2) and that he himself “investigated everything carefully from the beginning” (verse 3). And yet the main reason Luke can be counted as RELIABLE, is because HE WAS INSPIRED BY GOD to write what he wrote! 1^st Peter declares of him and all other authors of the Bible: “Holy men of God spoke as they were moved by the Holy Spirit” (NKJV). So, besides receiving written and oral reports from others, he received divine direction from the Holy Spirit! God was no doubt pleased to use the testimonies of “eyewitnesses and servants of the word” to aid Luke in writing the gospel, but God chose the very words that he would write. 2^nd Timothy 3:16 and 1^st Corinthians 2:13 confirm this: “All Scripture is given by inspiration of God….These things we also speak, not in words which man’s wisdom teaches but which the Holy Spirit teaches.”
2. Luke’s PURPOSE and DISTINCTION of his book. Luke’s “purpose” is seen in verse 4, “So that you may know the exact truth about the things you have been taught.” He wanted Theophilus to know, with absolute certainty, the “exact truth” that he had been taught. He knew this would result in him being “established in the truth” and that his faith in Christ was rooted in historical facts. Luke also wanted him to have a written account so he could refer to it whenever he wanted to, without having to rely on his memory or the memory of others. This is seen clearly in his words, “It seemed fitting for me as well…to write out for you.” And of course, this wasn’t just written for Theophilus; it was written for every believer in the Lord Jesus Christ. We can praise God for the Holy Scriptures being preserved so that we too can “know the exact truth!”

There is another PURPOSE too, which is related to the DISTINCTION of his book. Luke was inspired to write about Jesus Christ as “the Son of Man.” Matthew wrote of Jesus Christ as “the King of Israel”; Mark’s theme portrays Jesus Christ as “the Perfect Servant”; and John’s gospel sets forth Christ as “the Son of God.” So, each gospel is DISTINCT, and the DISTINCTION of Luke’s gospel is to reveal Christ’s True and Perfect Humanity. This is not revealed in the introductory verses that we have been considering, but as you study this precious book you see that more is written of His birth, His childhood, His moral perfections, His sympathy and compassion for mankind, His prayer life, and His agony as He anticipated His death on Calvary to save men, than in any other gospel. (234.5) (DO)