“So are you an atheist, or an agnostic?”

Both. I am an agnostic atheist.

Theism is a belief in a god (or gods). Atheism is a lack of belief in a god (or gods). Consider the question: “do you believe in any gods?” If your answer is “no”, “I don’t know”, silence, or anything except “yes”… you’re an atheist. That’s the first dimension.

Gnosticism is knowingness or certainty. Agnosticism is non-knowingness, or uncertainty. Consider the question: “Do you know for certain that a god exists or doesn’t exist?” If your answer is “no”, “I don’t know”, silence, or anything except “yes”… you’re agnostic.

You can be an agnostic theist, a gnostic theist, an agnostic atheist, or a gnostic atheist. Though, in practice, gnostic atheists tend not to exist. The sort of person who is skeptical about supernatural claims tends not to express absolute knowledge of something for which they have no evidence. Most people who say “God does not exist” or “no gods exist”, when pressed, would be shown to be technically agnostic, even if they only give an infinitesimally small bit of consideration to their uncertainty.

It’s true, I will sometimes say “God does not exist” or “there is no god”. But this is little more than a colloquial shortcut. What would you say if a child asked you if monsters hide under their bed? Would you say “I don’t know… maybe…”? I sure hope not. You’d say “no”. Even though the concept of monsters existing and being under a child’s bed is not unfathomable and you cannot say for sure that it never happens, you say “no”, because this is how we talk casually about things for which there is no evidence. It is an artifact of being asked a yes or no question to something which is neither “yes” nor “no” — it is simply unknown.

Now that I’ve made things clear, let’s complicate them. I am an agnostic atheist in general. What I mean, is, I cannot say for sure that no conceptions of “God” exist. You could always come up with a conception of a god that could never be disproven. You could make complete undetectability one of this god’s attributes. But you could also attribute very specific attributes or even interference in specific worldly events to this god. That changes the game. If you say, for example, that God exists because rain is his tears, falling from heaven, then I could say for sure that your idea of God is false, and that god doesn’t exist. I could be a gnostic atheist about that god, because the conditions of his existence are testable, and the idea of this god doesn’t past the test.

So while in general I am an agnostic atheist, with regards to specific ideas of gods that have been shown to be false, I may express more certainty about their non-existence.