24 Amongst these principles the main one lays down that as all men are alike by race and nature, so in like manner all are equal in the control of their life; that each one is so far his own master as to be in no sense under the rule of any other individual; that each is free to think on every subject just as he may choose, and to do whatever he may like to do; that no man has any right to rule over other men. In a society grounded upon such maxims all government is nothing more nor less than the will of the people, and the people, being under the power of itself alone, is alone its own ruler. It does choose, nevertheless, some to whose charge it may commit itself, but in such wise that it makes over to them not the right so much as the business of governing, to be exercised, however, in its name.
Source: Immortale Dei (Vatican.va)