2 Corinthians 13:5-6 (NASB)
5 Test yourselves to see if you are in the faith; examine yourselves! Or do you not recognize this about yourselves, that Jesus Christ is in you—unless indeed you fail the test?
6 But I trust that you will realize that we ourselves do not fail the test.
Paul, it seems, thought it was possible for others to discern that he "passed the test" and was, indeed, a born-again child of God. And so, he urged his readers to realize that he was "in the faith," just as they (hopefully) were, too.
Many Christian today, however, bridle fiercely at the idea that such a thing is possible. I suppose this has to do, at least in part, with the hyper-"tolerant," toxically-affirming and reality-denying "equality" that modern, western societies have taken up. No one must be told they are "less than," or immoral, or worst of all, a sinner. And the Church, powerfully infected by this society-collapsing "compassion," widely forbids the idea that anyone should be told they aren't saved when they've claimed that they are. Consequently, the Church in the West is profoundly corrupted with the "leaven" of false converts, desperately weakened spiritually and utterly unattractive to the lost. If the Church doesn't begin to guard itself carefully against the "leaven that leavens the whole lump" (1 Cor. 5:6; Gal. 5:9) it will eventually cease to be the Church, becoming only a counterfeit of it, "professing to know God but in works denying Him" (Tit. 1:15-16).
In light of the horror of the story Jesus told in Matthew 7:21-23, the real Church, truly born-again people, have powerful incentive to disabuse the lost of the notion that they are saved when they clearly aren't. The Church ought not to be a place where the unrepentant wicked feel at ease, even confirmed in their sin. That in so many churches they are, participating in Sunday morning worship services from lives swollen and sickly with sin, is a sharp indictment of those churches. Ironically, and awfully, such "affirming," "welcoming," all-embracing churches are the least loving (in an agape sense), smoothing the lost person's way to hell and keeping them far from God while encouraging them to think they're held in His arms. Horrible.