17 Reading the Encyclical within the context of Pope Leo's whole magisterium, we see how it points essentially to the socio-economic consequences of an error which has even greater implications. As has been mentioned, this error consists in an understanding of human freedom which detaches it from obedience to the truth, and consequently from the duty to respect the rights of others. The essence of freedom then becomes self-love carried to the point of contempt for God and neighbour, a self-love which leads to an unbridled affirmation of self-interest and which refuses to be limited by any demand of justice. This very error had extreme consequences in the tragic series of wars which ravaged Europe and the world between 1914 and 1945. Some of these resulted from militarism and exaggerated nationalism, and from related forms of totalitarianism; some derived from the class struggle; still others were civil wars or wars of an ideological nature. Without the terrible burden of hatred and resentment which had built up as a result of so many injustices both on the international level and within individual States, such cruel wars would not have been possible, in which great nations invested their energies and in which there was no hesitation to violate the most sacred human rights, with the extermination of entire peoples and social groups being planned and carried out. Here we recall the Jewish people in particular, whose terrible fate has become a symbol of the aberration of which man is capable when he turns against God. However, it is only when hatred and injustice are sanctioned and organized by the ideologies based on them, rather than on the truth about man, that they take possession of entire nations and drive them to act. Rerum novarum opposed ideologies of hatred and showed how violence and resentment could be overcome by justice. May the memory of those terrible events guide the actions of everyone, particularly the leaders of nations in our own time, when other forms of injustice are fuelling new hatreds and when new ideologies which exalt violence are appearing on the horizon.
Source: Centesimus Annus (Vatican.va)