Three-Fold Definition of the Church
Hence it is evident that a definition of the church cannot be given so agreeing with its various acceptations as fully to express their nature. In vain do the Romanists labor in giving a definition which can be accommodated to all the passages of Scripture where the word “church” is found. For it must be conceived of in different ways according to its threefold relations. For with respect to the first (which is the most proper and the principal), it is rightly defined as “an assembly of elect persons, whom God by his word and Spirit calls out of the state of sin into the state of grace unto eternal glory.” With respect to the second (which is less proper), it is said to be “a society of persons called by the preaching of the gospel to the profession of one faith, communion of the same sacred rites and observance of the same order.” Finally, with respect to the third, “an assembly of the rulers and pastors of the church, who are furnished with a lawful calling and the power to preach the word in it, administer the sacraments and exercise holy discipline, so that all things may be done decently and in order to the glory of God and the public edification of all.”
Francis Turretin, Institutes of Elenctic Theology, ed. James T. Dennison Jr., trans. George Musgrave Giger, vol. 3 (Phillipsburg, NJ: P&R Publishing, 1992–1997), 9.