The desire to harmonize the differences between the canonical Gospels can be traced back to the second century, when Tatian (a second-century apologist) combined the four Gospels into one document known as the Diatessaron (Greek for “out of four”). This combined Gospel was used in the Syrian churches in the third and fourth centuries until it was replaced by the four canonical Gospels in the fifth century.

Material Common to More than One Gospel

All four Gospels portray Jesus as leading a group of disciples, preaching, healing, performing miracles, being crucified, and being raised from the dead. Matthew was written for a Jewish or Jewish Christian audience, reminding them that Jesus fulfills the Hebrew Scriptures. Mark was written for a Gentile audience, focusing more on narrative than on teaching and portraying Jesus as a man of miraculous, powerful action. Luke shows Jesus as one who is especially concerned for the poor and those on the fringes of society. John explains that Jesus, the eternal Word of God, is not a second god, but rather the one true God, sent by the Father to renew Israel.

People who are familiar with the content of the Gospel stories often confuse the information from different accounts. For example, there is actually no single story in the Bible about a “rich young ruler”: only Matthew describes the man as young (Matt. 19:20), and only Luke mentions that the man was a ruler (Luke 18:18).

Some material is found in all four Gospels, including information about John the Baptist, the miracle of the feeding of the five thousand, and the story of the crucifixion and the resurrection (although the individual accounts of the resurrection differ). Some material appears in three Gospels, especially in Matthew, Mark, and Luke. These three Gospels have therefore been labeled the “Synoptic Gospels” (syn = together, optic = view). Stories found in all three Synoptic Gospels include the transfiguration (Matt. 17:1–13; Mark 9:2–13; Luke 9:28–36); the healing of Jairus’s daughter and of a woman with a flow of blood (Matt. 9:18–26; Mark 5:21–43; Luke 8:41–56); and the rich young ruler (Matt. 19:16–30; Mark 10:17–31; Luke 18:18–30). The details do not agree in every respect in each account, but clearly they represent the same story and exhibit linguistic dependence on the same source(s).

A significant amount of material appears in two of the four canonical Gospels. Matthew and Mark have the story of a Syrophoenician woman (Matt. 15:21–28; Mark 7:24–30), and both Mark and Luke tell the story of a widow’s offering to the temple treasury (Mark 12:41–44; Luke 21:1–4). The most significant body of teachings and sayings found in two Gospels is the material shared by Matthew and Luke. Each of the Gospels contains material that does not appear in any other Gospel. Mark has the smallest amount of such material, John the largest.

The Gospel of John and the Synoptic Gospels

Based on a study of the material common to more than one Gospel, and the material unique to one Gospel, John’s Gospel usually is seen as distinct from the other three. The most likely explanation for this is that John was written later, with knowledge of the other Gospels, and therefore the author saw no need to repeat most of this material (except what was central to his purposes). Some of the distinctive features of John’s Gospel are the use of terminology such as “love,” “light,” “life,” “truth,” “abide,” “knowledge,” “world,” and the “I am” statements. Furthermore, certain Synoptic terms are either rare or absent—for example, “kingdom,” “demons,” “power,” “pity,” “gospel,” “preach,” “repent,” “parable,” “tax collector.” More so than the Synoptics, John is written from the vantage point of the resurrection and with the aid of hindsight as well as the Spirit. This is why the author of John’s Gospel does not refrain from adding commentary to Jesus’ words (e.g., 2:21–22; 7:39; 11:51–52; 12:16).

The Synoptic Gospels are more interrelated. In passages that appear in these three Gospels, there is often very close verbal agreement between them (e.g., the healing of the leper [Matt. 8:2; Mark 1:40–44; Luke 5:12–14]; the question of Jesus’ authority [Matt. 21:23–27; Mark 11:27–33; Luke 20:1–8]), implying a common source. In many sections that are found in all three Synoptic Gospels, two agree extensively and the third diverges (e.g., Matt. 20:24–28 and Mark 10:41–45 against Luke 22:24–27). When two Gospels agree and one disagrees, Matthew and Mark often agree against Luke, and Luke and Mark often agree against Matthew; but Matthew and Luke do not often agree against Mark and never do so in regard to the order of material. At other points, the Gospel accounts diverge quite significantly when referring to the same events. The infancy narratives in Matthew are quite different from those in Luke. The two accounts of the parable of the wedding banquet (Matt. 22:2–14; Luke 14:16–24) differ so significantly that it is difficult to decide whether they are two versions of the same parable or two different stories. Reports on the resurrection diverge across all four Gospels.

It is possible that these similarities and differences can be traced back to the oral presentation of the gospel. Apostolic preaching would have formed itself into set ways of retelling the events of Jesus’ ministry through repetition. These accounts may have been told originally in Aramaic before being translated into Greek to facilitate the Gentile mission. The authors of Matthew, Mark, and Luke could have been drawing from this common tradition in writing their Gospels. There is probably a degree of truth to this theory, but it cannot explain all the data. The theory does not account for similarities and differences in the order of events, nor does it explain why Matthew and Luke always return to Mark’s order after they deviate from it. A common oral tradition does not adequately explain similar editorial comments (e.g., cf. Matt. 24:15 with Mark 13:14), which suggest a common written source.

Some have argued that the apostles or others wrote records of the words of Jesus (memorabilia), which were collected and written down topically, from which the Synoptic Gospels were composed. As the church grew numerically and geographically, various collections of these memorabilia were made. Again, this is not beyond the realm of possibility; however, working against this theory is the complete absence of any reference to such records. Furthermore, as with the oral theory, it does not explain agreement in the order of material. It does, however, highlight the probability that the evangelists were using written sources.

Markan Priority and Q

On the assumption that the writers of the Synoptic Gospels employed a written source(s), several scholars have tried to reconstruct this original written Gospel from the material in the Synoptic Gospels. This document, which scholars call the Urevangelium (German for “original Gospel”), ended up bearing very close similarities with the Gospel of Mark. This is not surprising, since nearly all of Mark is repeated in Matthew and Luke. This led to the belief that Mark was the most primitive Synoptic Gospel, and that it was a common source for Matthew and Luke.

This belief in Markan priority, which has gained increasing popularity since the nineteenth century, has helped explain the similarities among the Synoptic Gospels. Traditionally, Matthew was thought to be the first Gospel to be written, hence the order of the Gospels in our NT. This belief in Matthean priority was upheld by several early church writers such as Augustine, who saw Mark as an abridgement of Matthew (Cons. 1.2). Augustine may have been more influenced by the traditional ordering of the Gospels than by an analysis of the Gospels themselves. Mark’s Gospel does not read like an abridgement; it is the shortest Gospel, but individual sections of it typically are longer and more detailed than in Matthew.

There are many reasons why the priority of Mark is probable. It is the shortest Gospel, containing 661 verses, whereas Matthew contains 1,068 and Luke contains 1,149. When their content is compared, 97.2 percent of Mark is paralleled in Matthew, and 88.4 percent of Mark is paralleled in Luke. It is easier to understand Matthew and Luke as using Mark and choosing to add additional material to it than to think of Mark as using Matthew, Luke, or both and deciding to omit material such as the birth narratives and the Sermon on the Mount. Mark has simpler Greek, which includes an extensive use of the present tense, redundancies (e.g., Mark 1:32: “that evening after sunset”; cf. Matt. 8:16: “when evening came”; Luke 4:40: “at sunset”), and various colloquialisms (e.g., the word for “mat” in Mark 2:4). Mark alone among the Gospels uses Aramaic terms such as abba (14:36), talitha koum (5:41), and ephphatha (7:34), although Matthew also mentions Eloi, Eloi, lama sabachthani (Matt. 27:46; Mark 15:34). It is easier to see how Luke and Matthew would have “improved” Mark than the reverse.

If we accept the priority of Mark, and Luke and Matthew’s dependence upon it, there are still the sections of Matthew and Luke that bear strong similarities with each other. From an analysis of the text of Matthew and Luke, it appears that these two evangelists did not know each other’s works. If one knew of the other’s work, why the divergence in some material such as the birth narratives? Alongside this, however, there are close similarities in other material: Matthew has 4,290 words that have parallels in Luke but not in Mark, and Luke has 3,559 words that have parallels in Matthew but not in Mark. The solution appears to be that Matthew and Luke were dealing with some material that they held in common, and that each of them also had other material that he drew on independently. The material held in common is commonly called “Q” (from the German word Quelle, meaning “source”); the material unique to Matthew is called “M” and that which is unique to Luke, “L.” Whether Q was a document is unknown, although it is more likely to be a collection of sources, as is also the case with M and L.

Many scholars argue that Q was a written rather than an oral source, based on the exact word parallels in the Greek text (e.g., Matt. 6:24 and Luke 16:13, where 27 of the 28 words are exactly the same). The presence of doublets (double accounts of the same incident) in Matthew and Luke may show dependence by the respective evangelists on both a Markan and a Q source (e.g., Luke 8:16; cf. Mark 4:21; Luke 11:33; cf. Matt. 5:15). Some scholars have tried to explain the sources geographically: Markan material originated in Rome, Q material in Antioch, M in Jerusalem, and L in Caesarea, but such speculations are far from proven.

Summary

Within all of this, in seeking to understand the harmony of the Gospels, it is important to be aware of what we do not know. Many of the solutions focus on a history behind the text to which we do not have access. Modern literary critics have tended to focus more on the text itself than its prehistory. There is merit in this because it affirms the priority of the text and allows the reader to understand how a part of the text functions within the larger literary unit. It also allows the evangelists to be more than collectors of sources, to have written distinctive theological accounts. Their different emphases may explain some of the differences between the Gospels. This approach, however, also has its dangers. Some who focus on the text over its original intent distance the text from the author’s purpose and therefore open the door for subjective interpretations that deny the difference between a correct and an incorrect reading of the text. It also raises the danger of reading an ancient text through modern eyes, losing sight of the original context.

The church has been well served by four Gospel traditions. The fact that esteem for the text has stopped overharmonization has been of great benefit, as the readers of the Gospels can appreciate various hues and emphases between the different accounts of the ministry of Jesus.