In general, we probably would do well to avoid trying to determine whether or not someone is a false convert. I feel a temptation lately to analyze one of my friends who exhibits signs that she may not genuinely know the Lord.
For that matter, I sometimes try to figure out if I was really saved as a teenager or if my true conversion occurred in the last 15 years. There’s ample evidence to support both positions.
Over the years I believed a lot of bad doctrine, but over those same years I believed a lot of solid doctrine as well. Over the years I justified some of my sinful behaviors, but over those same years I grieved over other patterns of sin in myself and desired to please the Lord. I have concluded that I can’t evaluate my past spiritual status. I can only say that on January 20, 1971 God put me on a path, and somewhere between then and 15 years ago He saved me.
If I can’t determine whether or not I was truly saved back in the day, I think I’d better exercise caution about judging my friend’s spiritual condition.
Certainly, many people who sincerely believe themselves to be Christians aren’t. I often write about false converts, convinced that evangelical churches overflow with them. And if your sin causes you to examine yourself to determine whether or not you’ve really been born again, praise the Lord!
And it follows that there are times that we can legitimately determine whether another person honestly follows Christ. Most often, when I see friends unapologetically embrace flagrant sin for an extended period, I can be reasonably sure that they never really knew the Lord in the first place.
18 Children, it is the last hour, and as you have heard that antichrist is coming, so now many antichrists have come. Therefore we know that it is the last hour. 19 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. ~~1 John 2:18-19 (ESV)
Usually, false converts can recite correct theology. They attest to the fact that Jesus died to redeem sinners and that He rose again. They say that the Bible is the Word of God and that Jesus is the only way of salvation.
But as life goes on, they manifest attitudes and behaviors that betray a faith in their own supposed righteousness, a desire to supplement Scripture with other philosophies and/or an attachment to the world. Church is more about providing a social network and spiritual experiences than about receiving God’s Word and serving Him. Knowing the Bible takes second place to hearing “God” speak personally.
Sadly, evangelical churches overflow with false converts. Worse, weak preaching keeps false converts from examining themselves to see if they are in the faith. We must continually test ourselves against Scripture (1 John is a good place to start) and challenge others to test themselves. Being a false convert has eternal consequences.