Answer
Well, Jesus tells us that in the church there will always be tares among the wheat, unbelievers present with believers. We can't always tell those apart, but we can assume that if someone's an unbeliever functioning in the context of the church, they will experience the common grace of God in powerful ways, and hopefully, those common ways of seeing God will lead to saving grace in their lives.
Answer by Dr. K. Erik Thoennes
Dr. K. Erik Thoennes is Professor of Biblical and Theological Studies at Biola University’s Talbot School of Theology.