The correct answer is: "he believed in the power of reason to improve human life"
The Enlightenment philosophers, such as Locke, Monstequieu or Rosseau. introduced ideas that challenged, and ended up derrocating, the power structures of the Old Regime. They promoted reason and the scientific method over religious dogmatism and superstititions.
The main principles developed were the following: and they are the following: definition of bills of citizens' rights, social contract (citizens electing political representatives to create goverment through suffrage, in opposition to the prevailing absolute monarchies), and the division of the powers of the state in order to avoid excessive power accumulation in certain sectors, and risks of authoritarism.
Benjamin Franklin shared these ideas and principles and tried to apply them in the United States.