They wanted to form a government that did not allow one person to have too much authority or control. The Articles of Confederation taught them that there was a need for a strong centralized government.
The answer is reason.
Philosophers of the Enlightenment believed that answer can be found
through reasoning. There were two types
of reasoning during that time. You have
rationalism that relies on deduction and Empiricism which deals with
experience. It took root due to the liberal atmosphere at the time.