Skeptic

One who is yet undecided as to what is true; one who is looking or inquiring for what is true; an inquirer after facts or reasons.

A doubter as to whether any fact or truth can be certainly known; a universal doubter; a Pyrrhonist; hence, in modern usage, occasionally, a person who questions whether any truth or fact can be established on philosophical grounds; sometimes, a critical inquirer, in opposition to a dogmatist.

A person who doubts the existence and perfections of God, or the truth of revelation; one who disbelieves the divine origin of the Christian religion.

Alt. of Skeptical