What is the relationship between the Synoptic Gospels and John?

Although the synoptic Gospels contain an abundance of common material and frequently “have the same view,” the Gospel of John contains a great deal of unique information, some 92 percent of its text being exclusive material.  This fact, combined with the Gospel’s often unique understanding of the person and mission of Jesus Christ, led the early Church father Clement to write, “Last of all, John, perceiving that the external facts had been made plain in the Gospel, being urged by his friends and inspired by the Spirit, composed a spiritual Gospel” (c. A.D. 150-215, Eusebius, Ecclesiastical History 6.14.7).  Implicit in this statement is the idea that John purposely avoided much of what the other Gospels had already recorded, focusing on events and teachings that had deeper spiritual significance.

Some scholars have noted, however, that the Gospel of John need not necessarily be a late composition.  Of the synoptic gospels, Luke has the greatest amount of unique material: approximately 41 percent is common to the other Gospels, and 59 percent is exclusive to Luke.  Some of this exclusive material actually seems similar to that found in John, raising the possibility that Luke used John’s gospel or John himself as a source.  Likewise, John’s differences from the Synoptics could suggest that he wrote before the language of the three synoptic Gospels had gained a sure footing.