skeptic

One who instinctively or habitually doubts, questions, or disagrees with assertions or generally accepted conclusions.

One inclined to skepticism in religious matters.

An adherent of a school of skepticism.

A member of an ancient Greek school of skepticism, especially that of Pyrrho of Elis (360?–272? BC).

Same as skeptical.

One who suspends his judgment, and holds that the known facts do not warrant a conclusion concerning a given fundamental question; a thinker distinguished for the length to which he carries his doubts; also, one who holds that the real truth of things cannot be known in any case; one who will not affirm or deny anything in regard to reality as opposed to appearance.

One who doubts or disbelieves the fundamental principles of the Christian religion.

An adherent of a philosophical school in ancient Greece.

One who doubts concerning the truth of any particular proposition; one who has a tendency to question the virtue and integrity of most persons.