What it means to be labeled a Christian

C.S. Lewis 'Mere Christianity' page 10-11

Now if once we allow people to start spiritualising and refining, or as they might say "deepening," the sense of the word Christian, it too will speedily become a useless word [as gentlemen did]. In the first place, Christians themselves will never be able to apply it to anyone. It is not for us to say who, in the deepest sense, is or is not close to the spirit of Christ. We do not see into men's hearts. We cannot judge, and indeed are forbidden to judge. It would be wicked arrogance for us to say any man is, or is not, a Christian in this refined sense. And obviously a word that we can never apply is not going to be a very useful word. As for the unbelievers, they will no doubt cheerfully use the word in the refined sense. It will become in their mouth's simply a term of praise. In calling anyone a Christian they will mean that they think him a good man. But that way of using the word will be no enrichment of the language, for we already have the word good. Meanwhile, the word Christian will have been spoiled for any really useful purpose it might have served.

We must therefore stick to the original, obvious meaning. The name Christian was first given at Antioch (Acts 11:26) to "the disciples," to those who accepted the teaching of the apostles. There is no question of its being restricted to those who profited by that teaching as much as they should have. There is no question of its being extended to those who in some refined, spiritual, inward fashion were "far closer to the spirit of Christ" than the less satisfactory of the disciples. The point is not a theological, or moral one. It is only a questions of words so that we can all understand what is being said. When a man who accepts the Christian doctrine lives unworthily of it, it is much clearer to say he is a bad Christian than to say he is not a Christian.