What has been said so far related to the Church Universal, or to the Church in its primary sense, namely, the "one fold," John 10, 16, or the communion of believers, Matt. 16, 18, which the Holy Ghost continuously gathers through the preaching of the Gospel, Rom. 11, 2-5. However, Scripture applies the term Church also to local congregations, 1 Cor. 16, 19; 1, 2; 11, 16; Acts 8, 1; Rom. 16, 16, which therefore are known as local churches (ecclesiae particulares). Such local churches are assemblies of believers, or Christians grouped together at one place, to preach the Gospel and administer the Sacraments, in short, to execute the Office of the Keys, Acts 20, 28; 14, 23. 27; 1 Tim. 3, 5; Matt. 18, 17; 1 Cor. 14, 23.
With respect to the relation between the Church Universal and the local churches, Scripture teaches clearly that these are not two different churches or two different kinds of churches, but the Church Universal consists of all true believers who are found in the local churches. Since it is God's will that all believers should be joined to local churches, all cases where an individual believer on account of special circumstances temporarily does not hold membership in a local church must be regarded as exceptional and hence require no consideration in this connection. Local churches therefore are true believers, or true members of the Church Universal, who are joined together in a visible communion for the purpose of executing the Office of the Keys, or the peculiar church-power which Christ has given to His Church on earth. This point must be clearly understood; for local churches, in the proper sense of the term, consist only of true believers.
All hypocrites, who are not members of the Church Universal, are likewise not truly members of local churches, Matt. 24, 32; 22, 12-14; 20, 10-16; 13,47--48. Their connection with the local churches is only external and accidental. Accordingly, when St. Paul addressed the local church at Corinth ("the church of God which is at Corinth"), he addressed its members as "those that are sanctified in Christ Jesus, called to be saints, with all that in every place call upon the name of Jesus Christ, our Lord," 1 Cor. 1, 2. This description certainly does not apply to the hypocrites (mali et hypocritae) who were joined to the church outwardly (ecclesiae admixti secundum societatem externam).
Again, when hypocrites manifest themselves as such, Christ distinctly commands that they should be excommunicated, Matt. 18, 15-18; for since they are not members of the Church, they should not disgrace or injure the local congregation by their presence, 1 Cor. 5, 6-13.
Lastly, all the divinely imposed obligations of the local churches presuppose that those who fulfil them are true believers; for these Christian duties can be performed rightly only by persons who are truly regenerate; e. g., mutual instruction and admonition, Col. 3, 16. 17; church discipline, Matt. 18, 15-18; 1 Cor. 5, 1-13; preservation of the true doctrine and spiritual guardianship over the teachers, Rom. 16, 17; Col. 4, 17; preaching the Gospel, 1 Pet. 2, 9 ; Christian conduct in the fear of God, 1 Pet. 3, 8-17; etc. Before hypocrites can become members of the local churches, they must first "repent and be converted," Acts 3, 19.
We therefore rightly define local churches as assemblies of true believers, who are gathered at a certain place for the purpose of preaching the Gospel and administering the Sacraments. If in a general way we apply the term also to heterodox congregations or even to antichristian cults, this is done in a wider sense, either by way of synecdoche, because also in heterodox local churches there may be members of the Church Universal, or improperly (improprie), i. e., according to the common mode of speaking (unchristian cults).