FYI: the use of "Gnostic" to describe absolutely anyone who claims knowledge annoys me. The Gnostics were a specific religious movement. Etymology is not definition. Calling anyone who claims to know something "Gnostic" makes no more sense than calling anything that's supposed to be universal "Catholic." It just creates confusion.
Yet when we have the term
Agnostic, it's well understood. I'm using the term gnostic (rather than Gnostic, not the lack of capitalization) to mean something which I have clearly defined. If you don't like it, then that's okay, but it doesn't invalidate my point. I'm perfectly happy to use a different word. Perhaps you'd be more comfortable with shnerffly and a-shnerffly atheists?
But anybody who has put some thought into the matter knows that all human knowledge is imperfect... and that the existence of a grocery store is subject to uncertainties even beyond that. Still, even people who realize all this don't go around saying that they're "agnostic" about these sorts of claims.
And yet I am completely gnostic about the existence of the grocery store down the street. I've been there many times. I was there yesterday. I know for a fact that it is there. Sure, it may have burnt down overnight, but that would imply things like loud sirens of firetrucks driving past that simply didn't happen. So the grocery store existing is so likely that I can be certain of it.
Do you regularly assign uncertainty to this sort of thing? When your significant other asks you to pick up some bread and milk on the way home, do you respond with "sure" or "I hope I can?"
You seem to be spending a lot of effort to quibble about this despite the fact that the meaning is clear. In such a case I would say sure, but that is not a guarantee that I definitely will. I could get hit by a car and be taken to hospital with many broken bones, in which case there will be no bread or milk. But such an event is so unlikely to happen that I can treat it as certain that I will be able to get the milk and bread.
Of course, if you know some way to make a promise that will render one invulnerable to things which would prevent the fulfillment of that promise, please let me know.
Wherever you put your personal line on the "certainty scale" where anything above it is certain enough that you don't feel the need to say you're "agnostic," if you call yourself "agnostic" about gods but not about other routine things still subject to uncertainties because of the limits of human knowledge, you're saying to the world that the existence of gods is uncertain to a higher degree than all those other things.
Given that I've gone grocery shopping many times and yet never seen any evidence for God, I doubt the two are very comparable. Extraordinary claims require extraordinary evidence, after all.