Is it possible to be an unconverted believer?
Certainly, in the sense that demons believe Jesus is who he said he was and did what Scripture says he did (James 2:19). Though such belief doesn’t save, it’s common across the world today. Just about every intoxicated person I meet on the street says he believes in Jesus. Scores of people I meet around the world—including some Hindus, animists, and Muslims—profess some level of faith in Christ. All kinds of halfhearted, world-loving church attenders confess belief in Jesus. Further, Jesus seems to make clear we can all profess publicly a faith we don’t possess personally (e.g., hear the cry of the damned in Matt. 7:21-23). So biblically and practically, it’s very possible for one to assent to certain intellectual truths about Jesus and even participate in various church practices—completely apart from supernatural regeneration of the heart.
– David Platt