What essential person, according to Machiavelli, is needed to form a republic? What must that person do to protect the republic as it ages?

The first Brutus helps to found the Roman Republic by overthrowing the old ruler and administering an oath to the people. Whom did he overthrow, what did the oath promise, and why is such an oath vital to the founding of the Republic?

Machiavelli says there are six forms of government, three bad and three good. The bad are tyranny, oligarchy (“government of the few”) and anarchy. Briefly name and define the corresponding three good forms of government.