Q. Which Gospel was written first?
A. The matter is complicated; scholars base their theories about which Gospel is prior on certain features of the four texts that can be interpreted in contradicting ways. Nearly all biblical scholars agree that Luke was not written first, and that John was written last, but the chief argument is whether Matthew or Mark came first.
The “Matthew first” position dates back at least to St. Augustine in the fourth century; it was generally accepted by Catholics until the mid-twentieth century. This hypothesis still has some support, in part because it carries the weight of ancient tradition and it follows the order in which the Gospels appear in the canon. The opposing hypothesis is that Mark was written first.
Matthew, Mark, and Luke display considerable overlap in their text. So one or more of them most likely drew some of their material from the others, to which they added their own unique material. In addition, they may have drawn from another source that was known to all of them.
Since Mark is the shortest Gospel, did Matthew and Luke draw from him, adding material from other sources? Or did Mark draw from Matthew, condensing his material? None of the hypotheses proposed to sort out the relationships between these Gospels is fully satisfactory. Each one fails to account for some feature of the four texts.
Those who claim Mark is the first Gospel written may offer various kinds of textual evidence, but usually there is also an anti-Catholic bias involved, noted by Catholic scholars and by some non-Catholic scholars as well. For example, the “Mark first” scholars typically go on to claim that the Matthew chapter 16 passages about St. Peter and the Petrine primacy are not part of the earliest tradition, but were added later. Such a claim seems to imply that the Gospel accounts have been falsified, a false notion that faithful Christians should reject.