A piece originally written by Nolan at The Reformed Libertarian.

So, you claim you are a Christian. What gives you the right to say that is what you are?

“For it is not the one who commends himself who is approved, but the one whom the Lord commends.”
- 2 Corinthians 10:18 (NIV; used throughout)

Are you a Christian because you believe in God, go to church, or grew up in a Christian home? Are you a Christian because you don’t swear, drink, or use illegal drugs? Are you a Christian because you’re cordial in your interactions with others? Are you a Christian because you are Reformed in your theology?

What does it mean to truly be a Christian?

According to Gallup, 77% of Americans claim they are Christians. While that percentage has been dropping over the course of the past few decades, 77% is still a sizable percentage of the American population. By identifying as Christian, what are these people saying about themselves?

You are not a Christian because you believe God exists:

“You believe that there is one God. Good! Even the demons believe that–and shudder.”
- James 2:19

You are not a Christian because of any outward behavior, however noble, that you perform:

“Woe to you, teachers of the law and Pharisees, you hypocrites! You are like white-washed tombs, which look beautiful on the outside but on the inside are full of the bones of the dead and everything unclean. In the same way, on the outside you appear to people as righteous but on the inside you are full of hypocrisy and wickedness.”
- Matthew 23:27-28

It’s not legalistic, as some would claim, to have a narrow definition of what constitutes a true believer. If the Bible is narrow on a particular topic, we are to be just as narrow on that topic out of our willful allegiance to God.

“But small is the gate and narrow the road that leads to life, and only a few find it.”
- Matthew 7:14

The Bible is explicit that eternal life is not for everyone. There are those who we know will not enter heaven and therefore are not Christians since Jesus Christ is the only way to heaven (John 14:6, Acts 4:12).

You are not a Christian if you are an unrepentant idolater, adulterer, homosexual, thief, coveter, drunkard, slanderer, or swindler (2 Corinthians 6:9-10). The Bible goes further in its exclusivity when Jesus says you are not a Christian if you have not experienced spiritual rebirth:

“Jesus replied, ‘Very truly I tell you, no one can see the kingdom of God unless they are born again.’”
- John 3:3

To be a Christian is to have been “born again” or literally “born from above” by repenting [turning away] from your sin [disobedient rebellion against God] and placing your faith [hopeful, confident, and informed trust] in Jesus Christ alone as your Lord [master of your life] and Savior [rescuer from God's righteous wrath]. This is salvation and it happens by God’s sovereign grace (Ephesians 2:8-9). Your faith is the means by which God saves you. To never have experienced this is to never have become a Christian. Without becoming a Christian in this way one cannot be a Christian.

Once you experience salvation, a true Christian will experience sanctification. Sanctification is the process by which God makes us less like ourselves and more like Him by the power of the Holy Spirit, which is given to us at the time of our salvation (Ephesians 1:13-14). Authentic salvation will always result in authentic sanctification, for Christians become “new creations” in Christ (2 Corinthians 5:17). True conversion leads to a life that is being continually transformed by God. The Christian life is a transformed life.

In our pluralistic society, all of this may sound rather exclusive. I am not being exclusive for the sake of it, but out of love. No Christian would want anyone to be fooled into believing they are something that they are not. When Christ judges you, I do not wish for you to be caught by surprise when you hear the words, “I never knew you. Away from me, you evildoer.” (Matthew 7:22-23)