Below is an excerpt from Chapter 11 of The Oxford Handbook of Reformed Theology , by Scott Amos. Dr. Amos is Professor of History at the University of Lynchburg.

Theological Contribution
De Regno Christi was not written as a theological treatise in the same sense as the works discussed elsewhere in the present volume, but rather as a call to implement what Bucer believed to be a desperately needed total reform of church and society and a plan of action to achieve this end. Yet the work did develop several important and interconnected doctrinal themes, central to which is his vision of the Kingdom of Christ, which he defines thus:
The Kingdom of our Savior Jesus Christ is the administration and care of the eternal life of God’s elect, by which this very Lord and King of Heaven by his doctrine and discipline, administered by suitable ministers chosen for this very purpose, gathers to himself his elect, those dispersed throughout the world who are his but whom he nonetheless wills to be subject to the powers of the world. He incorporates them into himself and his Church and so governs them in it that purged more fully day by day from sins, they live well and happily both here and in the time to come.
(Bucer 1955: 54; here, 1969: 225)
In other words, the Kingdom of Christ is the church, which Bucer seeks to restore; restoration is a concept that he repeats frequently in this work, by which he means
returning the church to its biblical and apostolic norms. In the passage quoted above, Bucer addresses himself to three major areas of theology which will serve to organize what follows. First, it is clear that the central focus in De Regno Christi concerns the church and its character in this world; second, he gives close attention to the mutually supportive relationship of the church and the governing powers of this world; and third, he devotes attention to what will be necessary for the subjects of the kingdom(s) to live well and rightly—the basic outline of the discipline of the Christian life.
The major theological contribution of De Regno Christi is ecclesiological. The vision and programme Bucer elaborates in this, his last book, points up the strong ecclesiological character of his thought found throughout his career, but especially in his final years (Hammann 1984; Van’t Spijker 1996). The church is identified as the body of Christ of which the faithful become members, and in whom the Holy Spirit dwells. The church is not a voluntary society, it is the creation of the Holy Spirit; citizenship in it is based on God’s election (Bucer 1955: 4; 1969: 177). In this respect, Bucer speaks of the fundamental necessity for its members to be born of the Spirit in order to enter the kingdom (Bucer 1955: 52; 1969: 222), and he argues that the Spirit informs every aspect of the life of the believer (Bucer 1955: 23; 1969: 194–5). The place of the Spirit in Bucer’s thought is, with the emphasis on the church, a major facet of his theology throughout his career (Stephens 1970).
However, Bucer’s doctrine of the church embraces more than the church, strictly speaking. It is true, as we have seen above, that he devotes a substantial portion of this
treatise to practical matters relating to the ministry of the church (its structures, the training and responsibilities of ministers, elders, deacons, its ceremonies, charitable
work), but his discussion of these matters is with an eye to the larger purpose of the treatise—advising on how to bring about restoration—and is set within a broader social and communal (if not cosmic) context. Christ’s Kingdom begins with and first becomes visible in the church, but through the church it will ultimately embrace, shape, and rule the world. Bucer has what can be termed a post-millennial eschatology, and thus an optimistic view of the spread of Christ’s Kingdom through preaching and teaching; it is a kingdom that comes by persuasion, not by edicts or conquest.
In expounding upon the Kingdom of Christ, Bucer also talks about the kingdoms of this world, specifically the kingdom of England, and the interrelationship of the two categories of kingdom in the present age, which raises theological questions concerning church and state. He does talk about the state, but it is mostly in reference to its relationship to the church; he develops no theology of the state to a degree that complements his ecclesiology, nor is he concerned about forms of government (though what he implicitly endorses could be termed a ‘monarchical republic’, to borrow a phrase from recent discussions of Elizabeth I’s reign (Ryrie 2009: 233)). It is, however, clear from De Regno Christi that Bucer’s view of the state has little of the darker hues one finds in Luther, on the one hand, or in those collectively designated as Anabaptists, on the other. In several respects, the state has many of the same functions with reference to its subjects/citizens as does the institutional church to its members, and it was the calling of both church and state to effect the reforms for which he called.
In reference to the role of the state in caring for religion, Bucer, like Calvin and unlike Luther, developed a theology of the Christian magistrate. The magistrate has a high calling in respect of his duty towards religion, and he must pursue the restoration of true religion with all he has, even if it meant exile or death (Bucer 1955: 7–8; 1969: 180). Bucer regarded the magistrate as a shepherd, and many of the exhortations directed towards Edward VI urged him to take up this role by means of actively promoting the restoration of a truly biblical form of the church. In some respects, this would have resonated with the Tudor concept of the royal supremacy, though one suspects Bucer’s emphasis on the mutual submission of the kingdoms of this world and the Kingdom of Christ (Bucer 1955: 14; 1969: 186–7) would have cut across the grain. However, Bucer does hold up Constantine and his ‘pious successors’ as a model for Edward to follow (Bucer 1955: 36–7; 1969: 207–9), which would fit well with the argument advanced in the 1530s that the realm of England was an empire. Indeed, it has been argued that Bucer regarded Constantine’s reign as the golden age to which Christendom should return (Dandelet 2007).
While Bucer argues that the church and the state are distinct, he also argues that they must act in concert, with the mutual submission noted above, a joint activity that is fundamental for the full manifestation of Christ’s kingdom in this world. The aim of this concerted action was to promote the rule of Christ in such a way that church and society become two ways of speaking of the same reality. The corpus Christi, the body of Christ as the body of believers, becomes the corpus Christianum, the Christian society, where the ecclesiastical and spiritual on the one hand and the secular and political on the other are combined into one under the rule of Christ. Bucer does not expect that everyone within a given realm (such as England) will be intentional Christians. He does recognize that there will continue to be a few who reject the Gospel, and he maintains they should receive a measure of toleration unless their impiety becomes manifest in open rebellion (Bucer 1955: 18, 50; 1969: 190, 221). However, he proceeds on the assumption that the Kingdom of Christ will have authority over all members of society.
In addition to promoting the spread of the Kingdom of Christ, it is the role of the ministers and the magistrates to cultivate and encourage among believers their fundamental vocation, which is to serve others. The doctrine of the Christian life, the life of the Kingdom, is thus another major area of theology that is developed in De Regno Christi. The Christian life is a life of mutual service in which the principle of brotherly love is to be supreme. In words taken from the title of one of Bucer’s earliest works (Bucer 1523), believers do not live for themselves, but for others (Bucer 1955: 10–11; 1969: 182–3)—a principle that is repeated throughout De Regno Christi. Bucer advances a view of the Christian life as corporate, not individualistic (Bucer 1955: 10–11; 1969: 182–3). Each person is to have a regard for others, and to submit to the needs of others, seeking their well-being (Bucer 1955: 21, 22, 25; 1969: 193, 194, 196). He strongly affirms the cardinal Protestant doctrine of justification by faith, but equally he argues that it should result in service to others as faith works through love (Bucer 1955: 26–7; 1969: 198). In this respect, we see again his emphasis on the role of the Spirit, for the gift of the Spirit precedes all, and the works that Bucer argues should be manifest in the lives of believers must be in and through the activity of the Spirit. Works apart from the Spirit are of no use; the Spirit is essential, and likewise works following from the gift of the Spirit are essential (Bucer 1955: 27; 1969: 199).
What was also essential to the Christian life was the practice of discipline. In De Regno Christi, Bucer maintained that discipline was the third function of the ministry, following the preaching of the Word and the administration of the sacraments. Discipline included, first, attention to each believer’s life and manners; here his emphasis on discipline was connected to the obligation of everyone (not just ministers and elders, though these individuals retained primary responsibility) to demonstrate a care for others, to watch out for others, to aid them when they stumble or fall (Bucer 1955: 70–73; 1969: 240–42). Discipline also included what Bucer terms penance, administered by ministers and elders towards those who have fallen into serious sin, and which is exercised through prayer and private confession; in serious instances, excommunication is to be used against the stubbornly rebellious, though rarely and with the aim of restoration to full communion (Bucer 1955: 73–8; 1969: 242–7). Discipline is an area of Christian teaching to which Bucer is recognized as having made a major contribution (Burnett 1994), and he makes very clear his firm conviction that it is essential to achieving all for which he calls in this book (Bucer 1955: 78; 1969: 247).
From The Oxford Handbook of Reformed Theology edited by Michael Allen and Scott R. Swain. Copyright © 2020 by Michael Allen and Scott R. Swain and published by Oxford University Press. All rights reserved.