The Founding Fathers were heavily influenced by the Enlightenment philosophies from their time. This is visible in the Constitution on the separation of powers and on the rights it establishes.
The government created by the Constitution is separated between three powers: Executive, Legislative, and Judiciary. This is evidence of the influence of Montesquieu (1689-1755), an important French philosopher who affirmed this was the better form to distribute power in a government because this way power stops power. This is the basis of the checks and balances system.
The presumption of all humans being equal and the right to freedom is a classic Enlightenment idea, where all men should be equal and free through the use of reason.