Geerhardus Vos offers some thoughts on the reality of the Kingdom when he wrote this;
The first thing to be noticed in the synoptical passages above quoted is the absence of every attempt at a definition of what the kingdom of God means. Jesus occupies historic ground from the outset. It is the kingdom, the well-known kingdom with which he presupposes familiarity, not merely on his own part but also on the part of his hearers. Our Lord did not come to found a new religion, but simply to usher in the fulfilment of something promised long beforehand. In the Old Testament God is frequently represented as the King of the Universe not only, but also as the King of Israel in a special, redemptive sense. He became so at the time of the deliverance from Egypt and the organization of Israel on the basis of the covenant, Ex. 19:4–6, cpr. Deut. 33:4, 5. In this sense God's kingdom first meant a present, real relation between Himself and his people, not something whose realization was expected from the future. Through the supernatural giving of the law and its administration and his direction of the course of history Jehovah exercises the functions of King in Israel. Later on, however, the conception of the kingdom, without losing its older meaning, obtains a distinctly eschatological sense. This development coincided with the development of Messianic prophecy, and both took place in dependence on the institution and further development of the human kingdom, especially that of the Davidic line.
The most important question connected with this central idea of our Lord's preaching concerns the exact nature of the order of affairs designated by it. Did He mean by the kingdom a new state of things suddenly to be realized in external forms, more or less in harmony with the current Jewish expectations, or did He mean by it, primarily at least, a spiritual creation gradually realizing itself in invisible ways?
For convenience sake these two conceptions may be distinguished as the eschatological and the spiritual-organic conception, provided it be kept in mind that these two are not logically nor historically exclusive. It is necessary, however, to make the distinction, because in modern writings both have in turn been pushed to an extreme in which they become exclusive each of the other.
The tendency at present among those who believe that Jesus was conditioned by his age and environment is to make his conception of the kingdom largely eschatological. On the other hand, where the originality and uniqueness of Jesus' teaching as over against the Old Testament and Judaism and Apostolic doctrine, are strongly emphasized, the opposite tendency appears, viz.: to eliminate as much as possible the eschatological elements and to ascribe to Him the idea of a kingdom entirely spiritual and internal.
A careful review of the evidence shows that the organic and eschatological conceptions are both present in our Lord's teaching. In reference to the eschatological side it is almost superfluous to establish this in detail. Our Lord repeatedly speaks of the kingdom as a state of things lying altogether above the sphere of earthly and natural life, being so different from the natural conditions that it could not be evolved from the latter by any gradual process; compare Matth. 8:11; 13:43; Mk. 14:25; Lk. 13:20, 29; 22:16, 29, 30.
It is of more importance to collect the references to the kingdom as a present, spiritual reality. In Matth. 12:20, Lk. 11:19, our Lord appeals to his casting out of demons by the Spirit of God as proof of the advent of the kingdom. According to Lk. 17:20, He declared that the kingdom does not come with observation, but is among or within men. And Lk. 16:16, makes the kingdom begin from the days of John the Baptist and immediately succeed the law and the prophets as the comprehensive name for the Old Testament dispensation. Both the present reality and the organic-spiritual character of the kingdom are most clearly taught in the great kingdom parables, Matth. 13, Mk. 4, Lk. 8. In several of these parables the point of comparison is taken from vegetable life, for the express purpose of illustrating the organic mode of its coming.
According to all three Evangelists Jesus was aware of having revealed in these parables a relatively new thought concerning the kingdom, which He designates "the mystery of the kingdom," Mk. 4:11. This mystery, this new truth, we may find in the revelation that the kingdom is realized gradually, imperceptibly, spiritually, for in comparison with the Jewish exclusively eschatological expectations this was so novel and startling a thought that it might be fitly called a mystery. Some modern advocates of the eschatological view have tried to escape from this conclusion by assuming, that in the original form of the parables, as they were delivered by Jesus, not the kingdom of God but the preaching of the word, as preparatory for the establishment of the kingdom, was referred to, and that the introductory formulas, as they now stand, were added by the evangelists, but there is no critical evidence to support this view. These formulas are not all alike and in part so idiomatic that one can hardly fail to detect in them Jesus' own manner of speech; compare Mk. 4:30.
Both these aspects of the kingdom, thus represented in our Lord's teaching must be carefully guarded from current misconceptions. The doctrine of an eschatological kingdom must not be confounded with the ordinary Jewish expectations of the coming age. The latter were national, political, sensual. It was inevitable that these expectations should more or less color the understanding of what Jesus taught concerning the kingdom not merely among the people but even among his disciples. But we have no right to identify our Lord's own ideas with such misunderstandings.
The Kingdom of God
BY GEERHARDUS VOS