Adherents to Christianity hold the four gospels of Jesus—Matthew, Mark, Luke, and John—in high esteem for their accounts of the life and teachings of Jesus. While many different compilations concerning Jesus were once in circulation among Christians, the Council of Nicaea in the fourth century narrowed the official canon to the aforementioned four gospels.
We have a surprisingly strong basis for determining the chronology of at least three of the four gospels, generally termed the “synoptic gospels.” Matthew, Mark, and Luke are termed the synoptic gospels because they contain significant overlapping information and follow a similar narrative. The Gospel of John, by contrast, follows a largely different narrative from the other three gospels.
The manner in which information in the synoptic gospels is assembled gives us a strong basis to determine that Mark was the first to be written, followed by Matthew and then Luke (John is generally considered the last gospel to be written). This is in part because Mark and Matthew share considerable content found only in those two gospels. Likewise, Matthew and Luke share share considerable content found only in those two gospels. Mark and Luke, by contrast, share almost no original material. Stories found in both Mark and Luke can almost always be found in Matthew as well. This suggests that Luke did not use Mark as a source for material. Instead, Matthew would have likely been a major source for Luke.
This is the point at which some assumptions come into play in scholarly analysis. It is conceivable that Matthew could have been the source for both Mark and Luke, but Mark is generally viewed as the better candidate for the earliest gospel. This is in part because it is the shortest. There is an implicit assumption that, as stories of figures are told and retold, those stories will become more detailed over time, not less. Mark is also the roughest in composition. Tenses sometimes change mid-sentence, and other grammatical errors can be found in the text. The language is far smoother in the other two synoptic gospels, perhaps suggesting that they are more polished versions of the earlier book. Finally, Mark leaves out some of the more controversial stories in the Jesus narrative. The best example of this is the virgin birth. It seems likely that, if Matthew predated Mark, the latter would have used the story to bolster the claim of Jesus’s divinity. In addition, skeptics of the virgin birth would assume that this was a later addition to accounts of Jesus’s life, and would see the absence of the story in Mark as evidence of the book being produced earlier.
While Mark is probably the earliest gospel of the modern biblical canon, it was likely not the earliest surviving textual reference to Jesus, as some of the Pauline Epistles are believed to predate Mark. These Epistles unfortunately give little insight into Jesus’s life. Complicating things further, most scholars also contend that a mysterious fourth document now lost to history, called the so-called “Q” document, supplied some of the information found in the synoptic gospels. If this Q document were ever found, assuming it exists, it could displace Mark from its pedestal. Given the unlikelihood of this occurring, it is probably safe to regard Mark as the earliest gospel.