Since the world is dotted with thousands of distinct institutions called churches, and since it is possible for institutions as well as individuals to become apostate, it is important to be able to discern the essential marks of a true and legitimate visible church. No church is free from error or sin. Only in heaven will the church be perfect. But there is a significant difference between corruption, which affects all institutions, and apostasy. Therefore, to protect the care and nurture of the people of God, it is important to define the marks of a true church.
Historically the marks of a true church have been defined as: (1) the true preaching of God's Word, (2) the use of the sacraments in accordance with their institution, and (3) the practice of church discipline.
(1) The Preaching of God's Word. Though churches differ in details of theology and in levels of purity of doctrine, a true church affirms all that is essential to the Christian faith. Likewise, a church is false or apostate when it officially denies an essential tenet of the Christian faith such as the deity of Christ, the Trinity, justification by faith, the Atonement, or other doctrines essential to salvation. The Reformation, for example, was not a struggle over trifles but over a cardinal doctrine of salvation.
(2) Administration of Sacraments. To deny or defame the sacraments instituted by Christ is to falsify the church. The profanation of the Lord's Supper or the willful offering of the sacraments to professed unbelievers would disqualify a church from being recognized as a true church.
(3) Church Discipline. Though the exercise of church discipline may at times err in the direction of either severity or latitude, it can become so perverted as to no longer be recognized as legitimate. For example, if a church openly and impenitently endorses, practices, or refuses to discipline gross and heinous sin, it fails to exhibit this mark of a true church.
Though Christians should be solemnly warned not to be schismatic in spirit or given to divisive or quarrelsome spirits, they must also be warned of the obligation to separate themselves from false or apostate communions. Every true church exhibits the true marks of a church to a greater or lesser degree. The reformation of the church is a never-ending task. We seek more and more to be faithful to the biblical call to preaching, the sacraments, and church discipline.