44 Pope Leo XIII was aware of the need for a sound theory of the State in order to ensure the normal development of man's spiritual and temporal activities, both of which are indispensable. For this reason, in one passage of Rerum novarum he presents the organization of society according to the three powers — legislative, executive and judicial — , something which at the time represented a novelty in Church teaching. Such an ordering reflects a realistic vision of man's social nature, which calls for legislation capable of protecting the freedom of all. To that end, it is preferable that each power be balanced by other powers and by other spheres of responsibility which keep it within proper bounds. This is the principle of the "rule of law", in which the law is sovereign, and not the arbitrary will of individuals. In modern times, this concept has been opposed by totalitarianism, which, in its Marxist-Leninist form, maintains that some people, by virtue of a deeper knowledge of the laws of the development of society, or through membership of a particular class or through contact with the deeper sources of the collective consciousness, are exempt from error and can therefore arrogate to themselves the exercise of absolute power. It must be added that totalitarianism arises out of a denial of truth in the objective sense. If there is no transcendent truth, in obedience to which man achieves his full identity, then there is no sure principle for guaranteeing just relations between people. Their self-interest as a class, group or nation would inevitably set them in opposition to one another. If one does not acknowledge transcendent truth, then the force of power takes over, and each person tends to make full use of the means at his disposal in order to impose his own interests or his own opinion, with no regard for the rights of others. People are then respected only to the extent that they can be exploited for selfish ends. Thus, the root of modern totalitarianism is to be found in the denial of the transcendent dignity of the human person who, as the visible image of the invisible God, is therefore by his very nature the subject of rights which no one may violate — no individual, group, class, nation or State. Not even the majority of a social body may violate these rights, by going against the minority, by isolating, oppressing, or exploiting it, or by attempting to annihilate it.
Source: Centesimus Annus (Vatican.va)