Have you ever known a Christian who didn't act like it? How do we deal with these folks? How do we know if they're saved?
People are always asking..."what about my friend, he says he's a Christian, but he doesn't go to church, doesn't read the Bible, so is he saved?" The quick response is to assume they were never saved to begin with because they aren't showing "fruit". Some suggest that their salvation didn't stick or wasn't genuine. Still others suggest that they might have been saved, but have lost it.
These responses are typically man's way of looking at it, both compromise the gospel to some extent by either front-loading the gospel or back-loading it. Front-loading adds works to do in order to be saved where-as back-loading adds works to prove to yourself and others that you are saved. In either case, it's works which are highly subjective.
So how can we know if someone is a believer or not? Charlie dives into this providing several practical answers that don't involve compromise but stand on the authority of God's word.
For further reading, checkout Charlie's GraceNotes on this specific topic.