The patricians' oppression of the plebeians after the restoration of Junius Brutus and the struggles and resistance caused by it constitute the soul of the new development and contain the secret of the greatness of Rome, the "key to universal Roman history," _clavis historiae Romanae universae._ Polybius's explanation of this greatness is too vague. He describes it as due to the virtue or the religion of the patricians and relates the facts of this virtue rather than their cause. Vico also criticises Machiavelli, at one time because he adduces certain civil and military institutions as the cause of Rome's greatness without investigating the cause of those institutions, that is to say the character of Roman society: at another time for adducing what was only a partial cause, the high spirit of the plebeians. He thinks Plutarch worst of all, since envy of the virtue and wisdom of Rome leads him to ascribe her greatness to fortune. The fact was that Rome subjugated the other cities of Latium and then Italy and the world because her heroism was still young, while among the other Latin peoples it had begun to decay. Thanks to this youthful vigour the patricians were strong enough to preserve their order and the religion which formed its foundation and safeguard (the nobles, Vico observes at this point, were always and everywhere religious, so that the first sign of contempt for religion among them is a symptom of national decadence); the plebeians were spirited enough to demand a share in religion, auspices and all civil rights; the lawyers, lastly, were wise enough to interpret the old laws and apply them to any new case that might arise, and strove with all their might to alter the text of these laws as little and as slowly as possible. These were the chief causes of the growth and permanence of the Roman empire; for in all its political changes it contrived to remain faithful to its principles. Prowess in war was another result of the rivalry of the orders; since the nobles were naturally consecrated to the safety of their country, as the only means of preserving the civil privileges of their order, and the plebeians accomplished brilliant deeds in order to prove themselves worthy of patrician honours. And when the Romans extended their conquests and their victories over the whole world, they made use of four rules which they had already applied to the plebeians within Rome itself. They reduced barbarian provinces to the position of clients by planting colonies in them: they granted civilised provinces bonitary tenure of their land: to Italy they gave the quiritary tenure: and to the municipia, the towns which had earned better treatment, they accorded the same equality with themselves which the plebs had finally won.