Empirical - Based on or relating to observational evidence. Thus an empirical fact would be a fact substantiated by evidence.
Enlightenment - A period in European intellectual history from the later seventeenth century to the early nineteenth characterized by confidence in reason and a willingness to challenge traditional assumptions.
Reason - The capacity for logical analysis and argument. "Reason" in this sense is related to the term "reasoning," which refers to logical deliberation or argument, and to the notion of giving "reasons" for one's beliefs. Enlightenment thinkers like Kant believed that reason could provide clear answers to basic philosophical, scientific, and political questions.
Will - The faculty that enables us to pursue a course of action and influence events in the world, as in "freewill," "an act of will," "impose your will on someone."