The Reformers’ Definition of a True Church
One of the earliest recorded definitions of the church is derived from the Apostle’s
Creed, and Christians everywhere have long confessed the belief in a ‘holy catholic
church’ and the ‘communion of the saints.’ The Nicene Creed (381) similarly
established the trinitarian faith and affirms that ‘[we believe] in one holy and catholic, apostolic church.’ This confession provided a framework for what became known as the church’s four attributes. These are unity, holiness, catholicity (universal in relation to the whole) and apostolicity (the apostolic faith and gospel) and this became the norm for the ancient and mediaeval church.
At the Protestant Reformation, the Roman Catholic Church had exclusively claimed these four attributes for itself institutionally, and in response to charges of schism, the Reformers sought to distinguish between a true and false church. Edmund P. Clowney observes that ‘for Luther and Calvin, the preaching of the apostolic gospel defined the true church’ but they also ‘continued to affirm the attributes from the Nicene Creed’ (Edmund P. Clowney, The Church, Downers Grove, Illinois: Inter-Varsity Press, 1995, pp 92, 101). Two primary marks (notae) were identified by these magisterial Reformers as the distinguishing outward characteristics that make a church a true church.
Calvin’s hugely influential Institutes expressed the view that these marks
apply to visible, individual churches as opposed to the invisible and universal
church (John Calvin, Institutes, 4: 1: 4 and 9, pp 1016, 1023). He states that ‘wherever we see the Word of God purely preached and heard, and the sacraments administered according to Christ’s institution, there it is not to be doubted, a church of God exists' (John Calvin, Institutes, 4: 1: 9, p 1023. The French Confession of Faith, XVIII, which Calvin prepared in 1559 also states the same two distinguishing marks).
Debate has continued concerning the attempt to discern where the lines should be drawn between falsity and purity and Calvin himself was undoubtedly aware of this complexity. He was prepared to allow for a measure of error but warns: ‘As soon as falsehood breaks into the citadel of religion and the sum of necessary doctrine is overturned and the use of the sacraments is destroyed, surely the death of the church follows—just as a man’s life is ended when his throat is pierced or his heart mortally wounded.’
For Luther as well as for Calvin, the two marks that define a true church are the preaching of pure doctrine and the administration of the sacraments (baptism and the Lord’s Supper). (Benjamin Charles Milner, ‘The Marks of the Church’ in Calvin’s Doctrine of the Church, Leiden, Netherlands: E. J. Brill, 1970, pp 99-133.)
It is clear that Paul had an all-consuming concern for the church to be well-ordered as his letter to Titus teaches. The church is to be governed by godly and qualified elders, who teach sound doctrine so that the church rests upon a sound foundation. Titus 1:5, 'This is why I left you in Crete, so that you might put what remained into order, and appoint elders in every town as I directed you—' and 2:1 'But as for you, teach what accords with sound doctrine'.