The Sermons on the Mount and Plain have slightly different settings and very similar audiences, the former giving rise to the different names (plain v. mount). These discrepancies and similarities have led to theories about whether they are accounts of the same event or of different events. The explanation that they are different events solves a whole host of other variations as well, including the vast differences in contents. Ultimately, how the two sermons relate to each other depends on questions of how the Gospels came to be written and where the authors got their information.
