A person who believes that it is not possible to know whether God exists or not.
The belief that it is not possible to know whether God exists or not. (Uncountable)
Although he was raised a Catholic, he was an agnostic for most of his adult life.(Cambridge)
If you are skeptical of your religion, you might have become agnostic.
agnostic about religion or belief
skeptical to religion
Skeptic
Unbeliever
Believer
Agnosticism
Agnostic