The description of Christians being "in the world, but not of the world" is open to numerous misinterpretations. Perhaps the most common is to interpret the description as if it is saying this: "be in creation, but not of creation." The majority of Christians are gnostics at heart, viewing our real selves as spirits/minds with knowledge of God entombed in bodies of flesh, awaiting creation's destruction rather than its redemption.
The church exists to remind us that we are creatures, and that that is a good thing. It is a good thing because God is known not outside of creation, but as one who has eternally become a part of it. Embodied life is therefore not a hindrance to living in obedience to the divine will, but is its divinely ordained form. And not only ordained, but experienced.
Since the Word became flesh and dwelt among us, transcendent divine authority has presented itself as worldly moral authority. It comes to us not as a mysterium tremendum which simply destroys all wordly order, but as creation restored and renewed, to which God is immediately present in the person of the son of man. The teaching and life of Jesus must be morally authoritative if we are not to be thrown back upon the gnostic gospel of a visitor from heaven who summons us out of the world.
- Oliver O'Donovan
Christians are nothing more and nothing less than imitators of the life of Christ in mortal bodies by the power of the spirit, with the hope that God will do for those bodies that which he did for Christ's.