Like Aristotle and Polybius, Adams feared that pure forms, especially democracies, were unstable and inevitably led to tyranny, because of man’s lust for power due to his fallen nature. Classic republics fared little better, because they, too, relied on human virtue to sustain them. Adams doubted that Americans possessed sufficient virtue, though strong government direction through support of religion and morality might have a positive influence. The “mixed government” of the Massachusetts Constitution of 1787 became the system of “checks and balances” of the United States Constitution which would augment reliance on the people’s virtue in sustaining liberty. As Madison wrote in The Federalist No. 51, to preserve liberty while allowing government to function, “A dependence on the people is, no doubt, the primary control on the government; but experience has taught mankind the necessity of auxiliary precautions.”