The parable of the wheat and the tares (Matthew 13:24-30) introduces the reality that there is a mixture of believers and unbelievers in local churches (c.f. Jude 4; 1 John 2:19). The terms visible church and invisible church are effective ways of describing this dichotomy. The visible church (that which we can see) can have both wheat and tares; believers and unbelievers. We may never know that a tare is in our midst unless they apostasize. Of course, God knows, and He is not fooled. The invisible church consists of all true believers, and only true believers. These are those who have the Spirit of Christ. We cannot see the Spirit, but we know His work (c.f. 1 John 4:6; Galatians 5:22-23).