The prophets of the Old Testament pondered the thought that God is the supreme king and that, by Him alone, all other kings rule. In that vision, the ruling power over all the forces of evil is given to the Son of Man.
In the New Testament, the advent of this kingdom has the one theme: do penance, for the kingdom of heaven is at hand. At every stage in Christ’s teaching, the advent of this kingdom, its various aspects, its precise meaning and the way in which it is to be attained, form the staple of His discourses; so much so that His discourse is called “the gospel of the kingdom.”
In Christ the kingdom is not so much a goal or a place to be attained; it is rather a state of mind; it stands for an influence that must permeate our minds, if we would be one with Christ and aspire to His ideals.