Vatican II: "Gaudium et Spes" on the Church in the modern world

All human activity is to find its purification in the Paschal mystery
Holy Scripture, with which the experience of the ages is in agreement, teaches the human family that human progress, though it is a great blessing for man, brings with it a great temptation. When the scale of values is disturbed and evil becomes mixed with good, individuals and groups consider only their own interests, not those of others.
The result is that the world is not yet a home of true brotherhood, while the increased power of mankind already threatens to destroy the human race itself.
If it is asked how this unhappy state of affairs can be set right, Christians state their belief that all human activity, in daily jeopardy through pride and inordinate self-love, is to find its purification and its perfection in the cross and resurrection of Christ.
Man, redeemed by Christ and made a new creation in the Holy Spirit, can and must love the very things created by God. For he receives them from God, and sees and reveres them as coming from the hand of God,
As he gives thanks for them to his Benefactor, and uses and enjoys them in a spirit of poverty and freedom, he enters into true possession of the world, as one having nothing and possessing all things. For all things are yours, and you are Christ’s, and Christ is God’s.
The Word of God, through whom all things were made, himself became man and lived in the world of men. As perfect man he has entered into the history of the world, taking it up into himself and bringing it into unity as its head. He reveals to us that God is love, and at the same time teaches us that the fundamental law of human perfection, and therefore of the transformation of the world, is the new commandment of love.
He assures those who have faith in God’s love that the way of love is open to all men, and that the effort to restore universal brotherhood is not in vain. At the same time he warns us that this love is not to be sought after only in great things but also, and above all, in the ordinary circumstances of life.
He suffered death for us all, sinners as we are, and by his example he teaches us that we also have to carry that cross which the flesh and the world lay on the shoulders of those who strive for peace and justice.
Constituted as the Lord by his resurrection, Christ, to whom all power in heaven and on earth has been given, is still at work in the hearts of men through the power of his Spirit. Not only does he awaken in them a longing for the world to come, but by that very fact he also inspires, purifies and strengthens those generous desires by which the human family seeks to make its own life more human and to achieve the same goal for the whole world.
The gifts of the Spirit are manifold. He calls some to bear open witness to the longing for a dwelling place in heaven, and to keep this fresh in the minds of all mankind; he calls others to dedicate themselves to the service of men here on earth, preparing by this ministry the material for the kingdom of heaven.
Yet he makes all free, so that, by denying their love of self and taking up all earth’s resources into the life of man, all may reach out to the future, when humanity itself will become an offering acceptable to God.