It is common today for scholars to hold Markan priority. This is the view that Mark wrote his Gospel first and the other Gospel evangelists wrote after he did. This view has become popular since the nineteenth century. Before that most biblical scholars believed that Matthew wrote his Gospel first. Since then many scholars have concluded that Mark was one of the two primary sources that the other Synoptic Gospel writers used, the other being Q.12There is presently no definitive solution to this problem of which came first.
Scholars favoring Markan priority base their view on the fact that Mark contains about 90% of what is in Matthew and about 40% of what is in Luke. Matthew and Luke usually follow Mark's order of events, and they rarely agree against the content of Mark when they all deal with the same subject. Matthew and Luke also often repeat Mark's wording, and they sometime interpret and tone down some of Mark's statements. Normally Mark's accounts are fuller than Matthew and Luke's suggesting that they may have edited his work.
However sometimes Matthew and Luke agree against Mark in a particular account. Luke omitted a large section of Mark's material including all of what is in Mark 6:45-8:26. Moreover in view of the traditional dating of Mark late in the 60s, if Mark wrote first, Matthew and Luke must have written after the fall of Jerusalem. This seems unlikely since that event fulfilled prophecy, but neither writer cited the fulfillment as such.13
All things considered I favor Matthean priority. However this debate is not crucial to the interpretation of the text.
