Why is Jesus Christ the Lord of the whole world?
Jesus Christ is Lord of the world and Lord of history because everything was made for his sake. All men were redeemed by him and will be judged by him.
He is over us, and the only One to whom we bend the knee in worship; he is with us as Head of his Church, in which the kingdom of God begins even now; he is ahead of us as Lord of history, in whom the powers of darkness are definitively overcome and the destinies of the world are brought to perfection according to God's plan; he comes to meet us in glory, on a day we do not know, to renew and perfect the world. We can experience his nearness especially in God's Word, in the reception of the sacraments, in caring for the poor, and wherever "two or three are gathered in my name" (see Mt 18:20). (YOUCAT question 110)
Dig Deeper: CCC section (668-674) and other references here.
Part 1: The Profession of Faith (26 - 1065)
Section 2: The Profession of the Christian Faith (185 - 1065)
Chapter 2: I Believe in Jesus Christ, the Only Son of God (422 - 682)
Article 7: "From thence He will come again to judge the living and the dead" (668 - 682)
I. HE WILL COME AGAIN IN GLORY ⇡
Christ already reigns through the Church... ⇡
"Christ died and lived again, that he might be Lord both of the dead and of the living."549 Christ's Ascension into heaven signifies his participation, in his humanity, in God's power and authority. Jesus Christ is Lord: he possesses all power in heaven and on earth. He is "far above all rule and authority and power and dominion", for the Father "has put all things under his feet."550 Christ is Lord of the cosmos and of history. In him human history and indeed all creation are "set forth" and transcendently fulfilled.551
549.
550.
551.
Eph 1:10; cf. 4:10; 1 Cor 15:24,27-28.
As Lord, Christ is also head of the Church, which is his Body.552 Taken up to heaven and glorified after he had thus fully accomplished his mission, Christ dwells on earth in his Church. The redemption is the source of the authority that Christ, by virtue of the Holy Spirit, exercises over the Church. "The kingdom of Christ [is] already present in mystery", "on earth, the seed and the beginning of the kingdom".553
552.
Cf. Eph 1:22.
553.
LG 3; 5; cf. Eph 4:11-13.
Since the Ascension God's plan has entered into its fulfillment. We are already at "the last hour".554 "Already the final age of the world is with us, and the renewal of the world is irrevocably under way; it is even now anticipated in a certain real way, for the Church on earth is endowed already with a sanctity that is real but imperfect."555 Christ's kingdom already manifests its presence through the miraculous signs that attend its proclamation by the Church.556
554.
555.
LG 48 § 3; cf. 1 Cor 10:11.
556.
Cf. Mk 16:17-18,20.
... until all things are subjected to him ⇡
Though already present in his Church, Christ's reign is nevertheless yet to be fulfilled "with power and great glory" by the King's return to earth.557 This reign is still under attack by the evil powers, even though they have been defeated definitively by Christ's Passover.558 Until everything is subject to him, "until there be realized new heavens and a new earth in which justice dwells, the pilgrim Church, in her sacraments and institutions, which belong to this present age, carries the mark of this world which will pass, and she herself takes her place among the creatures which groan and travail yet and await the revelation of the sons of God."559 That is why Christians pray, above all in the Eucharist, to hasten Christ's return by saying to him:560 Marana tha! "Our Lord, come!"561
557.
558.
Cf. 2 Thes 2:7.
559.
LG 48 § 3; cf. 2 Pet 3:13; Rom 8:19-22; 1 Cor 15:28.
560.
Cf. 1 Cor 11:26; 2 Pet 3:11-12.
561.
Before his Ascension Christ affirmed that the hour had not yet come for the glorious establishment of the messianic kingdom awaited by Israel562 which, according to the prophets, was to bring all men the definitive order of justice, love and peace.563 According to the Lord, the present time is the time of the Spirit and of witness, but also a time still marked by "distress" and the trial of evil which does not spare the Church564 and ushers in the struggles of the last days. It is a time of waiting and watching.565
562.
Cf. Acts 1:6-7.
563.
Cf. Isa 11:1-9.
564.
Cf. Acts 1:8; 1 Cor 7:26; Eph 5:16; 1 Pet 4:17.
565.
Cf. Mt 25:1, 13; Mk 13:33-37; 1 Jn 2:18; 4:3; 1 Tim 4:1.
The glorious advent of Christ, the hope of Israel ⇡
Since the Ascension Christ's coming in glory has been imminent,566 even though "it is not for you to know times or seasons which the Father has fixed by his own authority."567. This eschatological coming could be accomplished at any moment, even if both it and the final trial that will precede it are "delayed".568
566.
Cf. Rev 22:20.
567.
568.
Cf. Mt 24:44; 1 Thes 5:2; 2 Thes 2:3-12.
The glorious Messiah's coming is suspended at every moment of history until his recognition by "all Israel", for "a hardening has come upon part of Israel" in their "unbelief" toward Jesus.569 St. Peter says to the Jews of Jerusalem after Pentecost: "Repent therefore, and turn again, that your sins may be blotted out, that times of refreshing may come from the presence of the Lord, and that he may send the Christ appointed for you, Jesus, whom heaven must receive until the time for establishing all that God spoke by the mouth of his holy prophets from of old."570 St. Paul echoes him: "For if their rejection means the reconciliation of the world, what will their acceptance mean but life from the dead?"571 The "full inclusion" of the Jews in the Messiah's salvation, in the wake of "the full number of the Gentiles",572 will enable the People of God to achieve "the measure of the stature of the fullness of Christ", in which "God may be all in all".573
569.
Rom 11:20-26; cf. Mt 23:39.
570.
571.
572.
Rom 11:12, 25; cf. Lk 21:24.
573.