The founders had a view of human nature. They wanted to use their views of freedom and equality to shape this country. The founders believed that as created beings we all have god endowed rights and a duty to protect and use them. And all humans have rational choice to do this and through rational capacity humans can create a government to help them protect and use their rights. The only powers government has are those powers consented by the people. A constitution is the superior law for making government laws. Government laws are the rules, consented through the constitution for daily living. .
According to early founding father James Madison, "Ambition must be made to counteract ambition. The interest of the man must be connected with constitutional rights of the place. It may be a reflection on human nature, that such devices should be necessary to control the abuses of government. But what is government itself, but the greatest of all reflections on human nature? If angels were to govern men, neither external nor internal controls on government would be necessary. In framing a government which is to be administered by men over men, the great difficulty lies in this: you must first enable the government to control the governed; and in the next place oblige it to control itself. A dependence on the people is, no doubt, the primary control on the government; but experience has taught mankind the necessity of auxiliary precautions." .
To check the power of government, arrange the government so that it would check it self. Use the inherent selfishness of man to work to control the government by giving the three branches of government shared powers so they can check each other's action. The constitution arranged for each branch to be selected from a different source at a different time. This way no one group could suddenly rise in power and trample on the rights of the minority.