The synoptic problem refers to scholars' attempts to understand the relationship among the gospels of Matthew, Mark, and Luke (known as the synoptic gospels because they have so much material in common).
Two solutions to this problem—the Q or two-source hypothesis and the Farrer hypothesis—begin with the premise that the first gospel to be written was Mark. What arguments are used to support this view?
The primary argument for Markian priority is the strong evidence that both Luke and Matthew redacted Mark's material. If Mark were a summary of Matthew, we would expect it to smooth out any rough edges. However the reverse is true. In the triple tradition, it's invariably Mark that has the rough edges that are smoothed out by Luke and Matthew.
Let's take the first passage found in Mark that is also found in Luke and Matthew:
As it is written in Isaiah the prophet, “Behold, I send my messenger before your face, who will prepare your way, the voice of one crying in the wilderness: ‘Prepare the way of the Lord, make his paths straight,’”—Mark 1:2-3 (ESV)
Note that while Mark says that the quotation comes from Isaiah, it's actually a merger of Malachi 3:1 and Isaiah 40:3. Whether Mark was following some standard practice or simply did not remember where the first stanza came from, attributing both to Isaiah has caused considerable confusion and seems to have spawned a textual variation ("in the prophets"). Matthew simplified the text by dropping the Malachi reference altogether:
For this is he who was spoken of by the prophet Isaiah when he said, “The voice of one crying in the wilderness: ‘Prepare the way of the Lord; make his paths straight.’”—Matthew 3:3 (ESV)
Luke makes the same edit, but also fills out the quotation a bit. It seems that he was interested in quoting down to "all flesh shall see the salvation of God" in order to further his theme that salvation also belongs to the Gentiles:
As it is written in the book of the words of Isaiah the prophet, “The voice of one crying in the wilderness: ‘Prepare the way of the Lord, make his paths straight. Every valley shall be filled, and every mountain and hill shall be made low, and the crooked shall become straight, and the rough places shall become level ways, and all flesh shall see the salvation of God.’”—Luke 3:4-6 (ESV)
If Matthew were first and Luke last among the Synoptics, we might expect Luke to match Matthew sometimes and Mark other times depending on which version fit his purposes best. But this seems somewhat rare. The more common pattern is that Luke follows Mark and ignores Matthew. For instance:
Peter answered him, “You are the Christ.”—Mark 8:29b (ESV)
Simon Peter replied, “You are the Christ, the Son of the living God.”—Matthew 16:16 (ESV)
And Peter answered, “The Christ of God.”—Luke 9:20b (ESV)
Peter's proclamation is the dramatic turning point of Mark, but the point is somewhat blunted if you don't associate "Christ" with the full range of Jewish cultural understanding of the Messiah. So Matthew added "the Son of the living God" to fill out the meaning of Peter's words. "Living God", in particular, pulls in many Scriptural references that add weight to the title. Luke also seemed to be aware that "Christ" might not be properly understood by his Gentile patron, so he added "of God". If he had had both texts open before him, it's difficult to see why he would have chosen to punch up Mark's bare-boned language rather than just taking Matthew's version.
Of all the New Testament texts, Mark preserves the majority of our Aramaic words and phrases attributed to Jesus. Luke and Matthew tend to drop these phrases when they are found in the triple tradition. They are more likely to retain Aramaic in material that is not found in Mark. The general pattern of the church as seen in Acts and Paul's letters was for the Greek-speaking believers to become more numerous than the Aramaic- and Hebrew-speakers. Therefore, it was sensible for the Gospel writers to translate words into Greek when they found them transliterated from Aramaic in their sources.
But if Mark were editing Matthew, it's difficult to understand why he would revert back to Aramaic. Presumably, including transliterations would only serve to confuse his audience.
While he does seem aware that many of his readers will not understand the words—Mark usually provides a translation—he uses them even when Luke and Matthew do not. (See for instance Mark 5:21-43, Matthew 9:18-26, and Luke 8:40-56.)
The most natural way to read this situation is that the gospel writers wanted to retain the Aramaic words of Jesus when they were remembered, but didn't bother to carry on the tradition once the words were recorded in another account. If this analysis is correct, Mark must have been first.
Finally, readers of the original language acknowledge that Mark's Greek is "unique". As Bruce Alderman notes:
Most translations won't show it (Young's Literal Translation does), but Mark often writes in ungrammatical Greek, switching from present to past tense and back—sometimes in the same sentence. Matthew and especially Luke don't make the same grammatical mistakes.
Even in English, Mark's way of telling his story seems different than in the other gospels. A causal reader will notice the reliance on the word "immediately" to move the action along. That sense of urgency is reflected in Mark's use of the present tense and the Greek word καί (meaning "and, also, even, indeed, but") to join phrases and stories. When I first studied Mark as a whole, I had no problem noticing that the long ending was written by another author even when reading a translation that evened out the language.
In sum, Mark has many, obvious problems that the other Gospels freely correct. One can easily imagine a scenario in which Luke and Matthew surveyed the existing accounts and found all of them, including Mark, lacking in various ways. Therefore, they decided to produce their own version of events combining the sources available to them. But it's harder to understand what could have motivated Mark to produce a version that does not take advantage of improved and corrected Greek
Markan priority is an answer to the question what is the precise literary relationship between Matthew, Mark and Luke, also known as the Synoptic problem. A close comparison of the first three gospels suggests that one or more of these writers had one or more of the other gospels before them as they wrote. This is more than a common oral tradition. Matthew, Mark and Luke have a fundamental literary agreement.
Mark Stein in his book the Synoptic Problem provides the following evidence for this precise agreement.
Agreement in Wording
While Matthew, Mark and Luke differ slightly from one another, when the tell the story, on the whole, they use the exact same words.
Agreement in Order
Stories are often arranged topically or non-chronologically in Matthew, Mark and Luke. And yet in their topical arrangement of stories Matthew, Mark and Luke exhibit remarkable similarities in order.
Agreement in Parenthetical Material
Parenthetical material are things clearly written by an author and not imbedded in the story itself. When parenthetical material appears one or more gospels it again suggests that someone was copy the other.
Unusual Agreements
The gospel writers occasionally differ in their quotations of Old Testament Scripture. However, when they do differ with Old Scripture they typically agree with one another.
Luke's Authorial Testimony
Luke also indicates that a literary relationship existed between his gospel and others (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.
All this evidence leads scholars to ask which gospel(s) came first? Again this is known as the Synoptic Problem. Which gospel(s) was/were used by the others?
For the following reasons scholars have singled out Mark's gospel as the first.
Mark’s Shortness
Mark is by far the shortest gospel. By word count Mark (11,025 words) is a little over half of the length of the Matthew (18,293) and Luke (19,376). Which is more likely that Matthew and Luke expanded upon Mark or that Mark combined and shortened Matthew and Luke? If Mark is shorter it seems more likely that Matthew and Luke expanded it.
Mark’s Poorer Writing Style
Colloquialisms and inferior writing style
In Mark 10:20 the rich young man replies to the question of Jesus concerning the commandments, “All these I have observed (ephylaxamen) from my youth.” The parallels in Matthew 19:20 and Luke 18:21 change the verb to ephylaxa.
In Mark 1:12 we read that after Jesus’ baptism the Spirit “drove” (ekballei) him into the wilderness to be tempted. The word in Mark is almost always negative. Thus, Matthew 4:1 reads “Jesus was led up (anechthe) by the Spirit,” and Luke 4:1 states that Jesus “was led (egeto) by the Spirit.”
Aramaic Expressions
Redundancy
Which is more likely? Matthew and Luke attempted to improve the language of Mark or that Mark devolved the style and grammar of Matthew and Luke? If Matthew and Luke have better language it seems more likely that Matthew and Luke improved upon Mark.
Mark’s Harder Readings
The Apparent Limitation of Jesus’ Power or Influence
Negative Descriptions of the Disciples
Miscellaneous Theological Issues
Which is more likely that Matthew and Luke cleared up some of the difficulties of Mark or that Mark created difficulties where none existed before. If Mark appears to exhibit an inferior picture of Jesus than its more likely that Matthew and Luke improved upon Mark.
Mark’s more Primitive Theology
Which is more likely that Matthew and Luke attempted to calibrate Mark’s theology to higher Christology or that Mark lowered the exalted Christology of Matthew and Luke?
Mark’s apparent lack of information on the Destruction of the Temple -
Which is more likely that Matthew and Luke added information about the temple destruction because they came later or that Mark, as the later gospel, took out information about the temple destruction from Matthew and Luke’s narrative
Accepting Mark makes sense of Matthew and Luke.
Probably the weightiest argument today in favor of Mark’s priority involves the comparison of the Synoptic Gospels in order to recognize and understanding their unique theological emphases. This is called Redaction Criticism. It's explored further in Jon Ericson's answer.
Off the top of my head, the biggest three that I can remember are:
Length: Mark is the shortest of all of the Synoptic Gospels. As the theory goes, future authors would be more likely to add information that was omitted by Mark
Overlap: Mark overlaps with both Matthew and Luke more significantly than Matthew and Luke overlap with each other.
Detail: The level of detail in Mark is greater than the others. e.g. the feeding of the 5,000 has Mark saying that the grass was green. Such detail would presumably be lost as the author was more temporally separated from the event.
I think "editorial fatigue" advanced by Mark Goodacre is probably the best evidence for Markan priority because it's the most straightforward, showing quite plainly the exact direction of sourcing. When considered along side the other internal evidence catalogued by previous answers to this question Markan Priority becomes virtually undeniable.
Sometimes where Matt improves upon Mark his edit is not sustained. Thus Mark's word's reappear in Matthew, betraying Mark's hand.
For Mark, Herod is called 'king' four times in the story of John's beheading. Matthew realizes the correct title was 'tetrarch'. which is correct: Herod Antipas is called 'tetrarch' by Josephus (is Matthew post-Josephus?). he misses one of the edits however, when he lapses into calling Herod the king halfway through the story (Matt 14.9), in agreement with Mark (6:26).
In the same story Matthew revises Herod's attitude toward John as antagonistic but yet retains a reference to Herod's grief over Herodais call for John's head:
Mark's version:
But she could not because Herod feared John, knowing that he was a righteous and holy man, and he protected him. When he heard him, he was greatly perplexed; and yet he liked to listen to him.' (Mark 6.19f).
25 ...Immediately she came in a hurry to the king and asked, saying, “I want you to give me at once the head of John the Baptist on a platter.” 26 And although the king was very sorry, yet because of his oaths and because of his dinner guests, he was unwilling to refuse her
Matthew's version
3 For Herod had laid hold on John, and bound him, and put him in prison for Herodias' sake, his brother Philip's wife. 4 For John said unto him, It is not lawful for thee to have her. 5 And when he would have put him to death, he feared the multitude, because they counted him as a prophet. 6 But when Herod's birthday was kept, the daughter of Herodias danced before them, and pleased Herod. 7 Whereupon he promised with an oath to give her whatsoever she would ask. 8 And she, being before instructed of her mother, said, Give me here John the Baptist's head in a charger. 9 And the king was sorry : nevertheless for the oath's sake, and them which sat with him at meat, he commanded it to be given her. 10 And he sent, and beheaded John in the prison. 11 And his head was brought in a charger, and given to the damsel: and she brought it to her mother. (Matthew 14:3-11)
odd that he be sorry for doing just the thing he had wanted to do but couldn't for political reasons. Herodais still manipulates her daughter to ask for Johns head in Matthew but we should expect Herod to be pleased not sorry.
At Jesus' trial
They took Jesus to the high priest; and all the chief priests, the elders, and the scribes were assembled. […] Now the chief priests and the whole council were looking for testimony against Jesus to put him to death; but they found none. For many bore false witness against him, and their witness did not agree. (Mark 14:53, 55–56)
And the high priest tore his garments, and said, “Why do we still need witnesses? You have heard his blasphemy.”(Mark 14:63–64a)
In Luke, the high priest is missing, no witnesses are called, and no false or contradictory testimony impedes the trial. However the council still exclaim that they have no further need of witnesses:
When it was day, the ruling body of elders of the people gathered, both the chief priests and the scribes, and they brought him into their council… Then all of them said, “Are you, then, the Son of God?” And he said to them, “You are saying that I am.” They replied, “Why do we still need witnesses? For we ourselves have heard it from his own mouth.” (Luke 22:66, 70–71)
This example in Luke points to his dependence on Mark as well for this narrative.
We should not try to answer this question just by reading English texts, but at least supplement this either by reading the Greek texts or referring to material written by those who can. The issue here is that Matthew, Mark and Luke contain passages that are consistently in the same order (suggesting copying) and frequently use exactly the same words in the Greek language. Once copying is established, then it is appropriate to ascertain which one was the original.
With Mark-Luke, this is easy, because of the 'Missing Block'. This is a substantial section of Mark, comprising a total of 74.5 verses from Mark 6:47 to Mark 8:27a, is missing from Luke. This results in the curious conjunction found in Luke 9:18 "And it came to pass as he was alone praying, his disciples were with him: and he asked them ..." These clauses are more meaningful when found in Mark at the start and end of the material missing from Luke - try it. It has been suggested that the person who provided the copy of Mark to the author of Luke realised that he would be offended by the passage in which Jesus called gentiles 'dogs' (Mark 7:27) and so removed that page and a further twelve pages so that the gap would not be apparent.
A technical proof of Markan priority is in the transmision of Markan intercalations. The (anonymous) author of Mark was a pre-eminent writer in the first century, and was the greatest known exponent of intercalations. Simplifying a little, intercalations were a literary device in the form A1-B-A2, which adds emphasis to both event A and event B. Of the nine undisputed (consensus they exist) Markan intercalations, Matthew retains them five times and Luke does four times, otherwise copying the content but not the structure. It is clear from this that the device moves from Mark to Matthew and to Luke, but not the reverse. In fact, the authors of Matthew and Luke probably thought it a rather strange style of writing.
Another argument in favour of Markan priority is that Mark is a very structured book, with every passage in exactly the right place from a literary point of view, using parallel and chiastic structures, as well as the intercalations mentioned above. To achieve this, it had to be the original, since the sequence of major events is the same in all three synoptic gospels. Although more general structure is found in the other gospels, especially Matthew, this is a remnant of the structure in Mark.
It appears from the earliest manuscripts that Mark originally ended at verse 16:8, with the young man telling the women that Jesus was risen, and they fled in terror, telling no one. This left the authors of Matthew and Luke with nothing to copy, but they certainly wanted to tell what happened next. This explains the very clear distinction between Matthew, where Jesus appeared (only) to the disciples in a mountain in Galilee, whereas in Luke, Jesus appeared to two of them on the road to Emmaeus, then in a room in Jerusalem.
Material that Matthew and Luke have in common, but absent in Mark, is explained by the hypothetical 'Q' document.
Awesome answers so far! One small thing I'd like to add is that Mark and Matthew often agree against Luke on the order of their narratives. Many times Mark and Luke agree against Matthew. But Matthew and Luke almost never agree against Mark. You can check it pretty easily yourself by looking at a harmony of the gospels. For instance, Matthew and Mark agree against Luke in Mt 12:46-13:35, Mk 3:31-4:34, Lk 8:4-18, while Mark and Luke agree against Matthew in Mt 8:2-4, 9:2-8, Mk 1:40-2:12, Lk 5:12-26. This phenomenon is difficult to explain except by Markan prioity.
Allow me to make one additional thought here. Some give great weight to the fact that many church fathers declared Matthew to be the first Gospel written. To many this makes impossible Markan priority.
I submit that Mark may still in a sense be much of the source of Matthew and Luke, even if Matthew and Luke were written first.
Here's how.
Let us assume there is some truth to the tradition that Mark wrote down Peter's Gospel in Rome in the 60's. Then consider the role of Peter among the apostles.
In the Jerusalem early church, the chief speaker for the apostles was many times Peter. And the apostles taught daily in the temple courts. So it is not improbable that Peter may have preached the daily Gospel sermon, repeating generally the same content each time. "Let me tell you about Jesus, who he was and what he did." Then the apostles divide the crowd into smaller groups and answer questions.
After a couple weeks, every apostle could almost repeat Peter's Gospel verbatim.
When Matthew traveled and decided what events from Jesus' life he would include in his own Gospel presentation there were changes from Peter's outline, yet in places of overlap it was easy to repeat exactly what Peter said. Eventually Matthew wrote down his gospel, the first one written.
Peter traveled from Jerusalem, and over the years his Gospel adapted some, making it different in some places from a few portions that Luke and Matthew repeated verbatim from the earlier Jerusalem days. These were subtle differences over 30 years of preaching the same Gospel sermon. Finally Mark joined him and eventually wrote down Peter's Gospel, as it was presented in Rome.
This scenario certainly makes some assumptions, a few with scant evidence, yet overall with possibly more evidence than a hypothetical Q document. It fits what we know of the priority of oral sermons, Peter's personality and propensity as speaker, the presence of the apostles together teaching in the temple, and some early church traditions. In essence, what some call Q may have been a common shared experience of Peter's oral presentation of the Gospel in Jerusalem.
Regarding Luke, one of the traditions is that Luke wrote down Paul's gospel. Paul received his knowledge of the life of Jesus by direct revelation (Galatians 1:11-12). Indeed it included facts not presented by the other gospel writers (details from the Last Supper, for example) and facts that should not have been known by anyone but God (the secrets Mary held in her heart, supposedly telling no one).
When Paul was in prison for two years in Caesarea, Luke had time to write down Paul's Gospel. He wanted to verify the facts. He had time to travel to Jerusalem, to hear Peter's Gospel either directly from Peter or from others who could quote it extensively, and to interview Mary to confirm the private stories. Matthew's written account might have been available. Luke would give some priority to the order of events as he had heard Paul present them multiple times, but having the other sources made his job writing easier.
Again, Peter's oral Jerusalem Gospel was a source for Luke, and was a little different from Peter's Rome Gospel which Mark would put in writing later.
Therefore the early traditions can be true - Matthew and Luke were written prior to Mark. Yet it can also be true that much of the content of Mark (Peter's Gospel) found its way into both Matthew and Luke.
Just an addition to what has already been explored in Mark's language. Particular words in Mark are changed in Matthew and Luke to make them more acceptable to their readers. In the healing of the paralytic man,Matthew uses "bed" (9:2 & 6), Mark uses "pallet" (2:4), Luke uses "couch" (5:19-24). Also, Mark in describing Peter after his denial of Jesus said,"He burst out weeping"(14:72), Matthew and Luke say,"He went out and wept bitterly" (Mtt 26:75 & Lk 22:62)
