... the temptation to use political force to establish a utopian state in this life:
Nevertheless, it cannot be forgotten that the manner in which the individual exercises his freedom is conditioned in innumerable ways. While these certainly have an influence on freedom, they do not determine it; they make the exercise of freedom more difficult or less difficult, but they cannot destroy it. Not only is it wrong from the ethical point of view to disregard human nature, which is made for freedom, but in practice it is impossible to do so. Where society is so organized as to reduce arbitrarily or even suppress the sphere in which freedom is legitimately exercised, the result is that the life of society becomes progressively disorganized and goes into decline.
Moreover, man, who was created for freedom, bears within himself the wound of original sin, which constantly draws him towards evil and puts him in need of redemption. Not only is this doctrine an integral part of Christian revelation; it also has great hermeneutical value insofar as it helps one to understand human reality. Man tends towards good, but he is also capable of evil. He can transcend his immediate interest and still remain bound to it. The social order will be all the more stable, the more it takes this fact into account and does not place in opposition personal interest and the interests of society as a whole, but rather seeks ways to bring them into fruitful harmony. In fact, where self-interest is violently suppressed, it is replaced by a burdensome system of bureaucratic control which dries up the wellsprings of initiative and creativity. When people think they possess the secret of a perfect social organization which makes evil impossible, they also think that they can use any means, including violence and deceit, in order to bring that organization into being. Politics then becomes a "secular religion" which operates under the illusion of creating paradise in this world. But no political society — which possesses its own autonomy and laws — can ever be confused with the Kingdom of God. The Gospel parable of the weeds among the wheat (cf. Mt 13:24-30; 36-43) teaches that it is for God alone to separate the subjects of the Kingdom from the subjects of the Evil One, and that this judgment will take place at the end of time. By presuming to anticipate judgment here and now, man puts himself in the place of God and sets himself against the patience of God.
Through Christ's sacrifice on the Cross, the victory of the Kingdom of God has been achieved once and for all. Nevertheless, the Christian life involves a struggle against temptation and the forces of evil. Only at the end of history will the Lord return in glory for the final judgment (cf. Mt 25:31) with the establishment of a new heaven and a new earth (cf. 2 Pt 3:13; Rev 21:1); but as long as time lasts the struggle between good and evil continues even in the human heart itself.
What Sacred Scripture teaches us about the prospects of the Kingdom of God is not without consequences for the life of temporal societies, which, as the adjective indicates, belong to the realm of time, with all that this implies of imperfection and impermanence. The Kingdom of God, being in the world without being of the world, throws light on the order of human society, while the power of grace penetrates that order and gives it life. In this way the requirements of a society worthy of man are better perceived, deviations are corrected, the courage to work for what is good is reinforced. In union with all people of good will, Christians, especially the laity, are called to this task of imbuing human realities with the Gospel.
From the May 1, 1991 encyclical, Centesimus annus.