Here is another excerpt from the classic book by C. S. Lewis, Mere Christianity:
"Here is another thing that used to puzzle me. Is it not frightfully unfair that this new life should be confined to people who have heard of Christ and been able to believe in Him? But the truth is God has not told us what His arrangements about the other people are. We do know that no man can be saved except through Christ; we do not know that only those who know Him can be saved through Him.
But in the meantime, if you are worried about the people outside, the most unreasonable thing you can do is to remain outside yourself. Christians are Christ's body, the organism through which He works. Every addition to that body enables Him to do more. If you want to help those outside you must add your own little cell to the body of Christ who alone can help them. Cutting off a man's fingers would be an odd way of getting him to do more work."