In his classic book, Gulliver's Travels, Jonathan Swift takes the reader on an adventure through other lands. And in those imaginary places, we discover that things are (on the surface, at least) quite different from the way they are here.
If they weren't so familiar to us, Jesus' teachings might read a little like Captain Gulliver's accounts -- strange and exotic. Jesus describes a way of living that is quite different from the way we live here. And in New Testament parlance, the difference is found in the distinction between two kingdoms.