C.S. Lewis on Theosis

Now the whole offer which Christianity makes is this: that we can, if we let God have His way, come to share in the life of Christ. If we do, we shall then be sharing a life which was begotten, not made, which always existed and always will exist. Christ is the Son of God. If we share in this kind of life we also shall be sons of God. We shall love the Father as He does and the Holy Ghost will arise in us. He came to this world and became a man in order to spread to other men the kind of life He has — by what I call “good infection.” Every Christian is to become a little Christ. The whole purpose of becoming a Christian is simply nothing else.

The command Be ye perfect is not idealistic gas. Nor is it a command to do the impossible. He is going to make us into creatures that can obey that command. He said (in the Bible) that we were ‘gods’ and He is going to make good His words. If we let Him⁠—for we can prevent Him, if we choose⁠—He will make the feeblest and filthiest of us into a god or goddess, a dazzling, radiant, immortal creature, pulsating all through with such energy and joy and wisdom and love as we cannot now imagine, a bright stainless mirror which reflects back to God perfectly (though, of course, on a smaller scale) His own boundless power and delight and goodness. The process will be long and in parts very painful, but that is what we are in for. Nothing less. He meant what He said.

The Church exists for nothing else but to draw men into Christ, to make them little Christs. If they are not doing that, all the cathedrals, clergy, missions, sermons, even the Bible itself, are simply a waste of time. God became Man for no other purpose. It is even doubtful … whether the whole universe was created for any other purpose.