Mike McKinley turns the question around (usually we ask "How Can I Know That I Am a Christian?") in a blog post relating to his new book, "Am I Really A Christian?". I would also point out that McKinley goes to 1 John to make his first four points. This is instructive for us when people ask us what are the marks of a true Christian. We should acquaint ourselves with the answers to be found in God's Word and they are found right there, in 1 John.
In II Corinthians 13:5, the apostle Paul commands his readers: Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test!
OK, that seems straightforward enough. But what does it mean to examine yourself? What should you be looking for? How do you know whether or not you are "in the faith"? What is the "test" that we might fail? I wrote Am I Really a Christian? in order to try to help answer these questions.
Well, we should all hope that we pass "the test" (again, Paul's words, not mine!). And Scripture gives us a few things to look for that would indicate that in fact we are not "in the faith". A few examples:
- You're not a Christian if you don't believe true doctrine: By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God, and every spirit that does not confess Jesus is not from God. (I John 4:2-3)
- You're not a Christian if you enjoy sin: Whoever says “I know him” but does not keep his commandments is a liar, and the truth is not in him, but whoever keeps his word, in him truly the love of God is perfected. By this we may know that we are in him: whoever says he abides in him ought to walk in the same way in which he walked. (I John 2:4-6)
- You're not a Christian if you don't persevere: They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us. (I John 2:19)
- You're not a Christian if you don't love others: Beloved, let us love one another, for love is from God, and whoever loves has been born of God and knows God. Anyone who does not love does not know God, because God is love. (I John 4:7-8)
- You're not a Christian if you love your stuff more than you love Jesus: And he said to all, “If anyone would come after me, let him deny himself and take up his cross daily and follow me. For whoever would save his life will lose it, but whoever loses his life for my sake will save it. (Luke 9:23-24)
Now, none of this is to say that our obedience somehow earns our salvation. But these are fruits of the regenerating work of the Holy Spirit that the authors of Scripture clearly expected a Christian to be able to discern in their lives.