Political rule is so natural and necessary to the human race that it cannot be withdrawn without destroying nature itself; for the nature of man is such that he is a social animal; for indeed brutes are so endowed by nature that each is sufficient to himself, but man needs so many things that he can in no way live alone. For brutes are born clothed and armed, and they have an instinct so determined toward all those things which are beneficial for them that by nature, without any teacher, they know at once how to build nests, to seek for food, and even to make medicine for themselves; but man is born without clothing, without a home, without food, lacking all necessities, and although he has hands, and reason, by which he can prepare all instruments, nevertheless each one needs a long time to develop, and so long that it is impossible for one man to be sufficient to himself for all necessities, especially since we are born unskilled, and the arts are learned rather by instruction than by experience; therefore it is necessary that we should live in society, and that one should aid the other.
Besides, even were each one sufficient to himself for the necessities of life, yet he would never, unaided, be able to protect himself from the attacks of wild beasts and robbers, but for this purpose it is necessary for men to assemble and to ward off attacks with their combined strength. And granted that one man might prevail against an enemy, yet he would always remain ignorant, and destitute of wisdom and of justice and of many other virtues, although, indeed, we are born for this very purpose, expressly to cultivate our mind and our will, for the arts and sciences were developed after a long time and by many men, and without a teacher they cannot be learned; it is impossible, moreover, to exercise justice except in society, since it is the virtue determining equity among many.
St. Roberto Bellarmino, De Laicis, Chapter 5