Why are there four Gospels instead of just one?
The reason there are four Gospels in the New Testament is that the church received the one good news about Jesus Christ through four witnesses. In other words, there are not four different "gospels" in the ultimate sense, but four canonical presentations of the one Christ…
The reason there are four Gospels in the New Testament is that the church received the one good news about Jesus Christ through four witnesses. In other words, there are not four different "gospels" in the ultimate sense, but four canonical presentations of the one Christ: Matthew, Mark, Luke, and John.
These four books tell of the same person, yet they do not repeat all the same details or emphases. Matthew strongly highlights Jesus' relation to Old Testament promises. Mark presents Jesus' actions and suffering in a faster and more concentrated style. Luke carefully develops the historical flow and the theme of salvation reaching broad groups of people. John is more selective and emphasizes Jesus' identity with theological depth. This diversity need not be a sign of contradiction. On the contrary, it offers multiple witnesses around a shared center. If one trustworthy witness is valuable in court, several witnesses who do not simply copy one another yet point to the same person can be even more illuminating.
The four Gospels also show that the memory of the early church was not mechanically uniform. Communities following the same Lord passed on his words and works within different needs and settings. For that reason, the Gospels carry not only historical testimony but also pastoral intention. Diversity here is not a problem, but a natural feature of credible witness.
The early church embraced these four together from a very early period. At times there were attempts to produce one harmonized Gospel or to treat other writings as equal, but the mainstream church preserved these four witnesses. Catholic, Orthodox, and Protestant traditions are united here.
So the question can also be asked, "Why were they not merged into one book?" The answer is that the testimony God left to the church is not flatly single-voiced but harmoniously multi-voiced. When the four Gospels are read together, the words, works, death, and resurrection of Jesus appear with greater richness. Instead of the simplicity one narrative might provide, the church was given the depth that comes from four witnesses.