As the author of a Gospel and the book of Acts, Luke is one of the most significant of the early church evangelists who were not among the Twelve, yet little historical data survives about him other than a few references to him in Paul's writing, which describes him as a “dear and beloved physician.” Catholic scholars have concluded that he was born in Antioch and was born a Greek, not a Jew, both of which facts seem to explain the partiality to gentiles and the city of Antioch that appears in his writings.

The origin of Luke's faith in Christ is not recorded. An ancient source speculates that he was a companion of Cleopas on the walk to Emmaus on the evening after the Resurrection. However, Luke's knowledge of the Septuagint (the Jewish Bible translated into Greek, which was the widely circulated version of the Bible in the first century) suggests that he may have been a convert to Judaism, though he could have also studied the Jewish Bible through his association with Paul and other apostles.

Luke's association with Paul is introduced in Acts 16:8–12, which relates Paul's “Macedonian call” to take the Gospel to Asia, and where the narrative point of view becomes the second-person “we,” rather than the more distanced third-person reporting style before this point. Though Luke's method of gathering the information on the life and ministry of Christ is less dramatic than Mark's method, the introduction to his Gospel is fairly specific about his method and his purpose: “Forasmuch as many have taken in hand to set forth in order a declaration of those things which are most surely believed among us, Even as they delivered them unto us, which from the beginning were eyewitnesses, and ministers of the word; It seemed good to me also, having had perfect understanding of all things from the very first, to write unto thee in order, most excellent Theophilus, That thou mightest know the certainty of those things, wherein thou hast been instructed” (Luke 1:1–4).

Though Luke's esteemed mentor Paul was not a disciple during Jesus' ministry, he received a divine revelation in the form of a vision set in heaven itself, which may have revealed facts and intentions of the Gospel that the eyewitnesses at the time missed or tended to ignore. Without seeming to boast, Luke is establishing his credentials as a scholar, saying that he has set out to establish all that could be learned about Jesus and the Gospel.

There is also a hint in this introductory passage that Luke was an eyewitness, “having had perfect understanding of all things from the very first.” But this could mean “from the very first hearing about them.” His stress that his account is “in order” suggests that he believes the events he describes are in the chronological sequence in which they happened, something that is missing from Mark's Gospel.