Book I, Chapter VII

Further, the whole human race is a whole with reference to certain parts, and, with reference to another whole, it is a part. For it is a whole with reference to particular kingdoms and nations, as we have shown; and it is a part with reference to the whole universe, as is manifest without argument. Therefore, as the lower portions of the whole system of humanity are well adapted to that whole, so that whole is said to be well adapted to the whole which is above it. It is only under the rule of one prince that the parts of humanity are well adapted to their whole, as may easily be collected from what we have said; therefore it is only by being under one Princedom, or the rule of a single Prince, that humanity as a whole is well adapted to the Universe, or its Prince, who is the One God. And it therefore follows that Monarchy is necessary for the welfare of the world.