freethinker.
http://www.ffrf.org/nontracts/freethinker.php
free-think-er n. A person who forms opinions about religion on the basis of reason, independently of tradition, authority, or established belief. Freethinkers include atheists, agnostics and rationalists.
No one can be a freethinker who demands conformity to a bible, creed, or messiah. To the freethinker, revelation and faith are invalid, and orthodoxy is no guarantee of truth.
How do freethinkers know what is true?
Clarence Darrow once noted, "I don't believe in God because I don't believe in Mother Goose."
Freethinkers are naturalistic. Truth is the degree to which a statement corresponds with reality. Reality is limited to that which is directly perceivable through our natural senses or indirectly ascertained through the proper use of reason.
Reason is a tool of critical thought that limits the truth of a statement according to the strict tests of the scientific method. For a statement to be considered true it must be testable (what evidence or repeatable experiments confirm it?), falsifiable (what, in theory, would disconfirm it, and have all attempts to disprove it failed?), parsimonious (is it the simplest explanation, requiring the fewest assumptions?), and logical (is it free of contradictions, non sequiturs, or irrelevant ad hominem character attacks?).