Are not mutually exclusive.

Four categories of belief.

1. Gnostic Theism
2. Gnostic Atheism
3. Agnostic Theism
4. Agnostic Atheism

1 - "I know there is divinity personified and hence believe in it."
2 - "I know there is not divinity personified and hence don't believe in it."
3 - "I don't know whether some personifiction of divinity exists but I believe in one."
4 - "I don't know whether some personification of divinity exists but don't believe in one."

Gnostic here doesn't mean gnostic in the sense of gnostic christianity, it's taken as meaning "with knowledge."

So when this kind of discourse happens:

"Do you believe in God?"
"...I'm agnostic."

Don't let them back out of the damn query.