Since saving faith, by which a person becomes a member of the Church, is solely the work of God, Eph. 1, 19. 20; 1 Pet. 1, 5; John 1, 13, the Church owes its existence and preservation entirely to divine grace, Ps. 100, 3; 1 Pet. 2, 9. 10.
Synergism, which makes man's faith depend in part on his meritorious efforts, therefore undermines the very foundation of the Church.
The means, or instrument, by which God gathers and sustains His Church is the Gospel in all its various forms of application (the Word and the Sacraments), through which the Holy Ghost engenders and preserves faith, Rom. 10, 13-17; 1 Pet. 1, 23-25. (Cp. Luther, St. L., V, 990 ff.; VI, 21 ff.)
Calvinism, which denies the efficacy of the means of grace and teaches the creation of faith by the immediate operation of the Holy Spirit, therefore removes the very foundation on which the Church rests. Fortunately the practise of Calvinists is more Scriptural than is their theory; for, unlike the consistent Quakers, they use and apply the means of grace; that is to say, they preach the Gospel and retain the Sacraments, though not in their Scriptural purity.
Believers are instrumental causes (causae instrumentales) of the Church inasmuch as they preach the Gospel and administer the Sacraments, Is. 40,9; Mark 16, 15. 16; Matt. 28, 20.
In this sense the visible Church on earth is the mother of all believers (mater fidelium), who like Isaac are children of the promise, Gal. 4, 26-28. Luther thus declares (St. L., IX, 573 ff., especially 575 ff.): "Sarah, or Jerusalem, is our free mother, namely, the Church, Christ's bride, by which we all are born. But she bears children without ceasing till the end of the world by the ministry of the Word, that is, by teaching and spreading the Gospel; for that is what to bear means. The Church should do nothing else than teach the Gospel in its truth and purity and thus bear children."
From this follows that the State (civil government) is not a sort of maid (ancilla ecclesiae) that must assist the Church in its divine work of winning souls for Christ. While both the papists and the Calvinists intermingle Church and State in principle and practise, the Lutherans, on the basis of Scripture, oppose every attempt to mingle the two. According to Lutheran doctrine the mingling of the two produces only harm, never any good (cp. church conditions in all European state churches). The Church loses nothing of its dignity or power by being independent of the civil government. On the contrary, its freedom from the restrictions of the civil law enables it to attend to its sacred duty of proclaiming the Word the more efficiently.
On the other hand, however, the independent constitution of the Church (die freikirchliche Verfassung) must not be interpreted as a sort of means of grace, which in itself makes it more effective in saving souls. Its success depends entirely on the testimony of the Gospel in its full truth and the administration of the Sacraments according to Christ's institution. That is both its privilege and its power.
With regard to the existing forms of government (absolute monarchies; limited monarchies; republics; Zwingli favored the republic; Calvin the oligarchy) the Augsburg Confession Art. XVI rightly affirms: "The Gospel teaches an eternal righteousness of the heart. Meanwhile it does not destroy the State or the family, bwt very much requires that they be preserved as ordinances of God and that charity be practised in such ordinances. Therefore Christians are necessarily bound to obey their own magistrates and laws, save only when commanded to sin; for then they ought to obey God rather than men, Acts 5, 29." The Augsburg Confession does not favor any particular form of government, but teaches that Christians must acknowledge, and be subject to, all "powers that be," Rom. 13, 1-7; Matt. 22, 21; 1 Pet. 2, 13. 17; 1 Tim. 2, 1-3; Jer. 29, 7.
While Christian believers who have been chosen to fill governmental offices must not conceal or deny their faith, but as earnest Christians witness the more faithfully to the truth of the Gospel, Acts 17, 34; Rom. 16, 23, wherever they have an opportunity, nevertheless they must carefully distinguish between the provinces of the Church and of the State, bearing in mind, on the one hand, that the State cannot be governed by God's Word or "Christian principles," but only by reason and common sense (lex naturalis), while, on the other, the Church is governed alone by God's Word and not by any dictates of reason or by the external coercion of laws . In other words, though Christians should put into the service of Christ also the influence which is theirs because of their high station in life, just as they so use their money and other talents, they must not intermingle the Church and the State in the interest of either of the two.
During the Reformation the prevailing conditions prevented Luther from carrying into effect his clear principle regarding the separation of Church and State; yet he never ceased to declare this principle as the only correct and Scriptural one. Cp. Christl. Dogmatik, III, 481 f.