Arguments for Markan Priority

The Argument from Length

The Gospel of Mark contains 661 verses, Matthew has 1,068 verses, and Luke has 1,149 verses. 

The use of Matthew and/or Luke by Mark seems unlikely because it would be strange for him to have omitted so much material. 

Some have argued that Mark was trying on purpose to produce an abridged gospel. This is unlikely in light of the fact that in the majority of the pericopes which the Synoptics do have in common, Mark is actually longer in those areas. See Robert H. Stein, Studying the Synoptic Gospels, pgs. 53-55 for a table giving such evidence. 

Mark's Poorer Writing Style: The Argument from Grammar

There are a few places in the Gospel of Mark where we find "inferior" grammar and expressions:

-In Mark 10:20, the word ephylaxamen is changed by Matt. 19:20 and Lk. 18:21 to ephylaxa. A change by Matthew and Luke is understandable, but if Mark used Matthew and Luke, why would he change it to have a more poor form of grammar?

-In Mark 2:4, the more colloquial term krabbaton ("pallet") is used. Matthew and Luke (in their parallel passages) change it to kline ("bed"). Once again, this change makes sense on the theory of Markan priority, but the Griesbach hypothesis does not have a coherent explanation for this. 

-In Mark 1:12, it says that after Jesus' baptism, the Spirit "drove" (ekballei) Him into the wilderness. Matt. 4:1 changes this to say Jesus was "led up" (anechthe), and Luke 4:1 does something similar. Why would Mark change a more positive term like anechthe to ekballei? 

In the Gospel of Mark, you have also the instances in which Aramaic expressions are recorded (Mark 3:17; 5:41; 7:35; 14:36; 15:34). In most (there are a couple exceptions) of the parallel verses in Matthew and Luke, these Aramaic expressions are omitted. Since Matthew and Luke's audiences were Greek-speaking, these omissions make sense. So far, I cannot find any proponent of the Griesbach hypothesis who has offered a coherent explanation for why Mark would have added Aramaisms into his gospel. 

The Lack of Matthew-Luke  Agreements Against Mark

B.H. Streeter in particular has formulated this argument as follow: Within individual pericopes, Matthew and Luke commonly agree with the wording of Mark, but hardly ever agree with each other against Mark's wording. This is what we would expect to find if each were independently using Mark's gospel.

In 1835, Karl Lachmann further observed that Matthew and Luke never agree in order against Mark, whereas there are time Matthew and Mark agree against Luke and where Mark and Luke agree against Matthew. This fact goes against the idea that either Matthew and/or Luke would have known each other's work. 

The Argument from Redaction

Another argument that scholars have given for Markan priority involves an investigation into each of the Synoptic Gospels' theological and literary emphases and practices. Most redaction criticism is done on the assumption of a Markan priority. This is because people think that a Markan use of Matthew and/or Luke would be unlikely. Here are two examples of how this would work:

1) Matthew constantly uses the title "Son of David" for Jesus (it appears 11 times in his gospel). Mark, on the other hand, only uses the title "Son of David" 4 times in his gospel. Luke also only uses it 4 times. When one examines the common pericopes in the triple tradition, it becomes apparent that part of the Matthean redaction is to emphasis the Jewishness of Jesus, by using the title "Son of David". The question, then, is this: is it more likely that Mark omitted this title from Matthew, or that Matthew added it into his Markan source? 

There are times when Mark and Luke both agree in not using the title "Son of David" when Matthew does use it. This would seem to imply that they were not using Matthew's gospel as a source (Stein). 

The fact that Mark and Luke are not adverse to the "Son of David" title shows that they were most likely not using Matthew.

2) Matthew also features what are known as the "fulfillment quotations". However, when Matthew uses this fulfillment formula, the parallel passages in Matthew and Luke (with one possible exception) this Matthean redactional practice does not appear there in those passages. Mark and Luke weren't uncomfortable in the least with the idea of Christ fulfilling Scripture, since this idea does feature elsewhere in their gospels (Mark 1:2; 7:6; 14:49; Luke 3:4; 4:21; 22:37). The reasonable explanation would be that Matthew is adding this to his Markan source, rather than Mark and Luke (for no apparent reason) omitting this Matthean emphases.