MATTHEW. MARK. LUKE. JOHN. The New Testament opens with four gospels, four stories centered on the life and ministry of Jesus. Have you ever wondered why four? After all, even a casual reading of the first three shows how similar they are. There’s a tremendous amount of overlap between Matthew, Mark, and Luke, with some sentences and passages being reproduced nearly verbatim.

If that were to happen today with four published biographies, someone would get sued for plagiarism.

The authors of the New Testament, of course, lived in a very different world than ours. They didn’t write for personal profit, and they weren’t concerned about royalties or intellectual property. Rather, they wrote for the edification of the newly founded movement of a diverse group of people who had devoted themselves to a Jewish Messiah named Jesus.

What grounded the teaching of that movement? People didn’t have books, podcasts, or the Internet. The gospels weren’t written until at least 30 years after the death and resurrection of Jesus. Even the letters of the apostle Paul didn’t get written until well over a decade after Jesus returned to the Father. In the meantime, as was normal for that time and place, they relied upon traditions and sayings that were passed along orally.

Still, given the tendency of people—even supposedly faithful ones!—to spin their own tales of who Jesus was and what he said, some authoritative account of his life was needed. Scholars agree that Mark was the first gospel to be written and John the last. John’s account, written sometime around the end of the first century, is in many ways quite different from the other three. Matthew, Mark, and Luke, therefore, are known collectively as the “synoptic” gospels (or simply, “the Synoptics”), a word that means they share a similar point of view as contrasted with John.

The commonly accepted theory is that both Matthew and Luke had Mark’s gospel in hand when they wrote their versions. They quoted from it extensively, but also modified it as suited their purposes. They also seem to have had at least one other source in common, probably a collection of sayings and teachings of Jesus. Scholars call this source “Q”—from the German word Quelle, which means “source”—but its existence is purely hypothetical.

Each of the gospel writers has his own theological agenda. They don’t write as journalists or even biographers; their purpose is more pastoral. Some have tried to “harmonize” the four gospels into a single chronologically-ordered account, but to do so loses some of the distinctiveness of the separate narratives. We need to read each story on its own terms to understand what the writer is trying to teach.

Thus, as we begin a long and deep dive into the third gospel, let’s get ourselves situated by tackling some basic questions. The first may sound like a trick question: who wrote the gospel of Luke?

The answer isn’t as obvious as it might sound. After all, the book doesn’t come with a byline naming its author. So who was Luke, and why is the gospel attributed to him?

The opening verses of both Luke and Acts are addressed to someone named Theophilus, who was probably the patron who supported the research and writing of both books. The book of Acts begins with these words:

In my former book, Theophilus, I wrote about all that Jesus began to do and to teach until the day he was taken up to heaven, after giving instructions through the Holy Spirit to the apostles he had chosen. (Acts 1:1-2, NIV)

“In my former book,” the author begins. It seems inescapable that the third gospel and the book of Acts were written by the same person—whether it was Luke or someone else—and to the same person, Theophilus. Scholars therefore refer to this two-volume work collectively as “Luke-Acts.”

Moreover, the author seems to have been a close colleague of Paul’s. Most of the book of Acts is written from a third person perspective: “Paul did this, Paul did that.” But there’s a sudden shift to the first person in Acts 16:10 as Paul as his companions left the city of Troas and sailed for Macedonia: “we got ready…we put out to sea…we stayed there…” The unnamed author inserts himself into the narrative.

So which of Paul’s colleagues was it? It may have been Luke, but unfortunately, that name doesn’t appear anywhere in the book of Acts. We only know that Luke was one of Paul’s associates from three of his letters, written to the Colossians, to Philemon, and to Timothy respectively. It’s only from Colossians 4:14 that we know Luke was a physician, and some readers have seen the touch of a doctor’s hand in the writing of Luke-Acts. The story of the woman with the bleeding disorder in Luke 8, for example, is written with more empathy for clueless doctors than the version in Mark 5; the description of a man’s illness in Acts 28:8 sounds like a clinical diagnosis. That has led some to suggest that the author of Luke-Acts must have been an associate of Paul who also had medical knowledge, and Luke is the only one we know of in the Bible itself who fits the bill.

But there’s other evidence outside the Bible. The oldest copy we have of the third gospel dates back to the end of the second century and is attributed to Luke. An even earlier document, a treatise called Against Heresies by the bishop and theologian Irenaeus, also names Luke as the author of both Luke and Acts.

Suffice it to say that if it had been heretical to attribute these books to Luke, someone would have said so. No one did, at least not convincingly. In the end, we’re left with a long-standing tradition that assigns the authorship of Luke-Acts to Luke, and no serious reason why we should believe otherwise. That’s the position we’ll take here.

The more important question, I think, is what Luke was trying to say. Why did he feel the need to go beyond what Mark had already said in his gospel? Let’s explore that next.