We've noted that scholarship accounts for the similarities between the gospels of Matthew, Mark, and Luke--the "synoptics"--by postulating that there is a literary relationship between them. This theory, known as "the priority of Mark," holds that Mark was composed first and was a source for the authors of both Matthew and Luke. The theory has considerable explanatory power, including the way in which it makes sense of why Mark's expectation of an imminent end to human history is blunted in both Matthew and Luke--it's because Matthew and Luke were writing later, and Mark's prediction hadn't come true. I suppose it's obvious that this is not a conclusion that our fundamentalist friends can tolerate, but it's a widely accepted tenet of New Testament scholarship.
Let's look rather closely at some of the textual evidence as it relates to a comparison between Mark and Luke. In Mark, the beginning of Jesus's ministry is described, at 1:14-15, in the following manner:
Now after John [the Baptist] was arrested, Jesus came into Galilee, preaching the gospel of God, and saying, "The time is fulfilled, and the kingdom of God is at hand; repent, and believe in the gospel."
The parallel passage in Luke (4:14-15) goes like this:
And Jesus returned in the power of the Spirit into Galilee, and a report concerning him went out through all the surrounding country. And he taught in their synagogues, being glorified by all.
The Markan emphasis on the content of the teaching--the time is fulfilled! the kingdom of God is at hand! repent!--is in Luke excised. If you lay the texts side-by-side, you see that this happens consistently. Perhaps the most startling example occurs near the end of the respective gospels, when Jesus is warning his followers about the end time. Mark (13:5-6):
And Jesus began to say to them, "Take heed that no man leads you astray. Many will come in my name, saying, 'I am he!' and they will lead many astray."
Luke (21:8):
And he said, "Take heed that you are not led astray; for many will come in my name, saying, 'I am he!' and 'The time is at hand!' Do not go after them."
Mark has Jesus say, "The time is at hand!" Luke has Jesus say, "Don't be led astray by anyone who says, 'The time is at hand!'"
What's often called "the Gospel of Luke" is actually the first installment of a two-part work that may be designated "Luke-Acts." The second part, the book known as the "Acts of the Apostles," or just "Acts," is a history of the early church. There is no question but that Acts is from the same hand as Luke and that the two books were conceived as a single composition. While deferring our discussion of Acts, let's just note that its very existence is of a piece with the theory that its author was concerned to defer the Second Coming to some indefinite future time, with the result that an interim period not foreseen in Mark could be filled with a narrative about the activities of the early Christian heroes.
Paying close attention to how the author of Luke-Acts handles, and alters, source material from Mark is one fruitful interpretive strategy. But of course not all of Luke has a source in Mark, which is by far the briefest of the four gospel narratives. The story of Jesus's nativity--the announcement to Mary, the census, the angels, the shepherds, the manger and the wise men bearing their gifts, all of that--is not found in Mark. Neither is there in Mark any appearance of the resurrected Christ. Another interpretive tool, therefore, is to separate out the portion of the Lukan narrative that has no parallel in the other gospels. The idea is that, to comprehend an author's cast of mind, pay close attention to what he says when he breaks away from his source. With regard to Luke, this approach yields quite a dramatic result.
Everyone knows that Jesus taught in parables. Which are the most famous and loved? The parable of the good Samaritan? It's found only in Luke. The parable of the prodigal son? It also is found only in Luke. The parable of the prodigal son closes out a chapter--chapter 15--that contains only material unique to Luke. The first half of the chapter is made up of the parables of the lost coin and the lost sheep. The widespread notion that Jesus has a particular concern for lost causes and outcasts--that he came "to comfort the afflicted and afflict the comfortable"--isn't made up by bleeding hearts. It comes from somewhere--mainly, from Luke. It's this aspect of the third gospel that stands behind the story of the priest who, accused of being a Marxist, replied that he was "Marxist as Luke."
The parables of the good Samaritan and prodigal son have attained such a degree of cultural familiarity that their sharp edges are now somewhat smoothed. The context for the former is a question from a lawyer about what is necessary to attain eternal life. Jesus asks him what the religious law requires. The lawyer, quoting Leviticus 19:18, answers perfectly--you are to love God with all your heart and mind and soul, and your neighbor as yourself. When Jesus concurs, the lawyer asks, "But who is my neighbor?" The parable of the good Samaritan is Jesus's answer to that question. The priest and the Levite who pass by on the other side of the road from the injured man are conventional figures of religiously reputable Jews. It is the Samaritan, a despised gentile, who goes out of his way to assist. In the parable of the prodigal son, the "good son," who resents the joyful welcome his father gives the prodigal, is more or less in the role of the priest and the Levite, now with a voice:
[H]e answered his father, "Behold, these many years I have served you, and I never disobeyed a commandment of yours, but you never gave me a goat, that I might celebrate with my friends. But when this, your son, came, who has devoured your living with prostitutes, you killed the fattened calf for him."
It is easy to think of this other son as the villain, but, really, who is being honest while congratulating himself for not being like him? His offense may be detected in his verbal constructions, for another way for him to say "this, your son" would have been "my brother."