The evidence of the Gospels for the teaching of Jesus

We have four gospels, and these four gospels are not direct copies of one another. But how can we understand the testimony of these gospels?

In this video, Dirk Jongkind takes a look at some of the questions surrounding the four gospels: What is a gospel and how does this help us to gain confidence in what we read? What happened to the teaching of Jesus in the first decades after his death and resurrection?