“As regards the conception of the kingdom of heaven in theology, this has been powerfully subjected to all kinds of influences and viewpoints during the various periods and trends of theological thought. In Roman Catholic theology a distinctive feature is the identification of the kingdom of God and the church in the earthly dispensation, an identification which is principally due to Augustine’s influence. Through the ecclesiastical hierarchy Christ is actualized as King of the kingdom of God. The area of the kingdom is coterminous with the frontiers of the church’s power and authority. The kingdom of heaven is extended by the mission and advance of the church in the world.
In their resistance to the Roman Catholic hierarchy, the Reformers laid chief emphasis on the spiritual and invisible significance of the kingdom and readily (and wrongly) invoked Lk. 17:20f. in support of this. The kingdom of heaven, that is to say, is a spiritual sovereignty which Christ exercises through the preaching of his word and the operation of the Holy Spirit. While the Reformation in its earliest days did not lose sight of the kingdom’s great dimensions of saving history, the kingdom of God, under the influence of the Enlightenment and pietism, came to be increasingly conceived in an individualistic sense; it is the sovereignty of grace and peace in the hearts of men. In later liberal theology this conception developed in a moralistic direction (especially under the influence of Kant): the kingdom of God is the kingdom of peace, love and righteousness. At first, even in pietism and sectarian circles, the expectation of the coming kingdom of God was maintained, without, however, making allowance for a positive significance of the kingdom for life in this world. Over against this more or less dualistic understanding of the kingdom we must distinguish the social conception of the kingdom which lays all the stress on its visible and communal significance. This conception is distinguished in some writers by a social radicalism (the ‘Sermon on the Mount’ Christianity of Tolstoy and others, or the ‘religious-social’ interpretation of, e.g., Kutter and Ragaz in Switzerland), in others by the evolutionary belief in progress (the ‘social gospel’ in America). The coming of the kingdom consists in the forward march of social righteousness and communal development.
In contrast to these spiritualizing, moralistic and evolutionary interpretations of the kingdom, NT scholarship is rightly laying stress again on the original significance of the kingdom in Jesus’ preaching—a significance bound up with the history of salvation and eschatology. While the founders of this newer eschatological direction gave an extreme interpretation to the idea of the kingdom of heaven, so that there was no room left for the kingdom’s penetration of the present world-order (Johannes Weiss, Albert Schweitzer, the so-called ‘thoroughgoing’ eschatology), more attention has been paid latterly to the unmistakable present significance of the kingdom, while this significance has been brought within the perspective of the history of salvation, the perspective of the progress of God’s dynamic activity in history, which has the final consummation as its goal.”