Another crucial theme in the Gospel of Mark that cannot be missed even by the most cursory of introductions is Jesus’ emphasis on the Kingdom of God. The first thing to a proper understanding of this theme is that the word kingdom doesn’t necessarily mean kingdom in the sense of a nation but in the sense of rule of God. The old Catholic Encyclopedia describes the expression as signifying “not so much the actual kingdom as the sway of the king”. In the Gospel of Mark, the first thing that Jesus preaches to inaugurate his ministry upon the death of John the Baptist is the imminence of the Kingdom of God: “The time is fulfilled, and the kingdom of God is at hand; repent, and believe in the gospel” (Mk 1:15). I can offer no surer explanation than the one described in the catechism, #2816:
“The Kingdom of God lies ahead of us. It is brought near in the Word incarnate, it is proclaimed throughout the whole Gospel, and it has come in Christ’s death and Resurrection. The Kingdom of God has been coming since the Last Supper and, in the Eucharist, it is in our midst. The kingdom will come in glory when Christ hands it over to his Father”.
The above paragraph highlights the historical, present and future eschatological aspect of the Kingdom. Historical, since already started by Jesus’ coming at a certain moment in time, and proclaimed by him throughout his ministry. This proclamation is continued by the apostles and their successors throughout history, and is made present for us in the Eucharist. It will be fulfilled at the end of times with Jesus’ second coming.