Created by the eternal Father, redeemed by the Word made flesh, and offered the gift of their Holy Spirit, we human beings are related to the members of the divine family not only as creatures to creator but as persons to persons. We are called to share in the intimate life of this family, to join its members in an eternal wedding feast (see Mt 22.2; Rv 19.7–9), to know them in fulfilling union even as we are known by them (1 Cor 13.12; 1 Jn 3.2). Communion in heaven will include the enjoyment of divine life itself (Rv 21.6–7); the present gift of the Holy Spirit is, as it were, only the first payment from the inheritance promised us as God’s children (see Eph 1.14).
We shall also enjoy fulfillment precisely as human persons. We are not souls only, but human, living bodies. Nor are we only intellects. We have intellects for knowing, but we also have wills for loving the goods we understand, senses for experiencing, emotions for feeling, and hands for making useful and beautiful things for human enjoyment and the praise of the Trinity. We shall give over to the Lord Jesus, our brother, the good fruits of our nature and our work done in the Spirit. In and through him we shall return to the Father all the gifts we have received (see Eph 1.10; 1 Cor 15.24).
Vatican II teaches: “. . . after we have obeyed the Lord, and in his Spirit nurtured on earth the values of human dignity, brotherhood and freedom, and indeed all the good fruits of our nature and enterprise, we will find them again, but freed of stain, burnished and transfigured. This will be so when Christ hands over to the Father a kingdom eternal and universal: "a kingdom of truth and life, of holiness and grace, of justice, love and peace’ [Preface of the Feast of Christ the King]. On this earth that kingdom is already present in mystery. When the Lord returns, it will be brought into full flower” (GS 39). The goods of the kingdom—truth, life, holiness, grace, justice, love, and peace—are divine blessings, but they are also fulfillments of aspects of what human beings can be. Insofar as they are good fruits of our nature and effort, they are created and redeemed; insofar as we who share in them share also in divine life, they are sanctified.
The kingdom will be brought to fulfillment only when the Lord comes. Without him we can do nothing (see Jn 15.5). But with him and with the grace of the Holy Spirit, we can and ought to contribute here and now to the building up of Christ in whose fullness we shall share in the kingdom (see LG 36). We can do this by respecting and defending the human goods of the kingdom insofar as they are goods of our nature, and pursuing and promoting them insofar as they can be good fruits of our work. It is God’s wish that our daily contribution to the building up of Christ, made in obedience to him and in the power of his Spirit, have eternal worth. Every morally good act of Christian living through the grace of the Spirit is therefore an act of cooperation in the work of the Trinity.
Here is a central and profound principle of Catholic life. The creative, salvific, and sanctifying love of the divine persons bears directly upon the goods proper to us as human persons; and our love for the divine persons, which is a gift of the Spirit (see Rom 5.5), also bears directly upon our own fulfillment and that of all humanity. As a man, the Lord Jesus has but one human heart to love his heavenly Father and his human fellows. Precisely because we are called to share in his divine life, we ought to strive to realize the fullness of human life in ourselves and others.
The rest of this book will be devoted to explicating this fundamental principle of a human life centered upon the Lord Jesus and embracing all things: “For all things are yours . . . and you are Christ’s; and Christ is God’s” (1 Cor 3.21, 23).