St. Thomas's purpose in writing the De Regno is to provide practical guidance for a Christian king on how he should exercise his authority. The king, imitating God, will lead his subjects to the end they deserve, and this will be nothing other than community virtue. This implementation of the practice of citizen virtue is the intrinsic purpose of political society and, for St. Thomas, it is the king's genuine concern to guide and direct citizens towards the common good. However, before dealing with the precise content of the common good of political society, and the specific means through which the king should realize it, St. Thomas will present two fundamental principles for his treatise: 1) that man is naturally a political animal; and 2) the common good is the proper purpose of political society. Before establishing the first principle, that man is political by nature, St. Thomas tells us that "in all things which are ordered to an end, in which this or that course may be adopted, some guiding principle is necessary through the which the intended purpose can be achieved by the most direct route". Since man is a being who has an end towards which his life and actions are ordered, it is necessary that he have some directing principle that leads him towards this end. This guiding principle for man is none other than reason. This guiding principle of reason, if it is good for man, is however not sufficient to reach his goal: «if man were destined to live alone, as many animals do, he would need no other guide to reach his goal. end, but every man would be a king in himself, under God, the supreme King, inasmuch as he directed himself in his actions with the light of reason given to him from above". It is true that man, for St. Thomas, more than any other animal will try to live in a group, because he is by his nature social and political. After these initial observations, St. Thomas will then proceed to argue dialectically to establish the truth of his first principle. Man has been given reason to provide for everything that is necessary for his life, but the individual man is incapable of providing for all these necessary things on his own. Furthermore, unlike other animals, every single man is not capable of creating all the things necessary for his life. Considering these two points together, Thomas arrived at his first principle: «It is therefore necessary for man to live in multitude, so that each can assist his fellow men, and different men are busy trying, with their reason, to make different discoveries , for example one in medicine, one in this and another in that”. Note that this statement of man's natural orientation to live in political society is not a fully developed explanation; Thomas has not yet underlined the unique difference of political society compared to all other associations. He will return to this point later, in chapter 3 of book 2, where he deals with the purpose of political society. After having established that man is political by nature, St. Thomas goes on to defend the reason why it is necessary for there to be a political authority that governs a multitude: “F...... middle of paper ......d the polis. Indeed, this hierarchical order allows Aquinas to articulate and defend the perfection of man as it exists within political society, and to show that it is ultimately inferior to that supernatural perfection attainable only through grace. Furthermore, this natural perfection is not opposed to the supernatural happiness of man, since grace presupposes and is based on the implementation of those virtues which are the common good of political society. Thomas concludes this section by reiterating a fundamental component of Catholicism, namely that ultimate happiness.