Given that there are no absolutes,
Are you
absolutely sure about that?

When an atheist states he is a strong/hard/gnostic atheist, I.E. Is he claiming that he can absolute know that gods do not exist? Or does he qualify it with the preset that absolute knowledge of anything cannot really be known?
What's a "god?" Until a coherent definition can be provided, it's a meaningless sound, like "blark" or "unie." How can you be certain that blarks don't exist? Do gods exist?
1. God: Anything that's a lot more intelligent and/or more powerful than us, e.g. Arthur C. Clarke's Monolith Builders (2001: A Space Odyssey) Sure, or at least I hope so. That would mean that there's hope for us to be able to keep growing.
2. God: A memetic brain-virus that employs myth, archetypes, and symbolism for purposes of software compression, enabling it to infect human brains and periodically take over their "personality hardware" to "run" the god persona as dominant, so that the god virus can be perpetuated, spread, and empowered. *Points at Bible* Yep.
3. God: "The synergetic integration of all known and unknown generalized operating principles of eternally regenerative scenario Universe" (R. Buckminster Fuller). Well, I don't see why not, but it's not something to pray to, and it won't stamp a "purpose and meaning for your life" on your forehead for you.
4. God: The character(s) of Yahweh/Jesus/the Holy Spirit as described in the Bible, as (a) real, externally-existent person(s) who authored the Bible as an infallible testament to his/their existence, nature, and activity. No. The Bible contradicts itself and reality on numerous points. "But how do you know God isn't hiding in the center of Arcturus? You'd have to know everything!" No I don't. It's enough to know that there was no Exodus as described in the Bible, that the Cosmos is not a few thousand years old, that Yahweh is not enthroned above the (flat) circle of the Earth, that the heavens are not his throne and the Earth is not his footstool, Jesus did not simultaneously uphold and abolish the Torah law before unleashing a zombie invasion of Jerusalem, and so on. If there's some creature hiding in the center of Arcturus that decides to come over here and represent itself as Yahweh/Jesus/the Holy Spirit, then it's a "god" of the first type above, not this type. If that. The Biblical "god" as portrayed therein is not very bright, and he did get his ass handed to him by people with iron chariots (Judges 1:15).
4. God: An omnipotent, omniscient, omnipresent, and omnibenevolent Being as described in Christian theology No. The "omni-" attributes logically contradict one another. An omnipresent being can't get lost (hence, not omnipotent), an omniscient being knows all of its own choices, thoughts, etc. and thus can't change its mind (not omnipotent), cannot experience surprise (not omnipotent), cannot commit an evil act (no free will, thus not omnipotent, and arguably not omnibenevolent either).
[1] And so on.
God: The Ground of Being, the object of ultimate concern, [insert "sophisticated" theological bafflegab here] Uh, what are you even
talking about? Can you specify any anticipated consequences we would expect to see if it exists, vs. if it does not exist? Provide a coherent definition of "god" and we'll talk.
So (as has also been demonstrated in the other posts above), the whole thing is a semantic game. Not just any game though: it's a theological/philosophical equivalent of a carnival barker's shell game. It goes like this:
ATHEIST: [Unleashes a brutal gang of facts on the Theist's claims, reducing their theological construct to a forlorn pile of tiny broken pieces]
THEIST: Well, yeah...but you can't
know there is no God! ["God" = definitional blank screen on which anything at all can be projected; the more vague the better] How do you know God isn't hiding at the center of Arcturus, eh, smart girl/guy? The only way you could know God doesn't exist is if you knew everything about every corner of the universe, but then you'd
be God! OH YEAAH! *does victory dance*
ATHEIST: OK, sure, I'm an agnostic atheist. I don't
know there is no god, but you haven't provided any reason to believe in one.
THEIST: [*Switcheroo engaged* "God" = character in their preferred Holy Book as understood and worshiped by their particular sect] Aha! Since you can't
know that God does not exist, then you've at least got to admit that it's
possible. *Steals the appearance of a degree of credibility for their ridiculous beliefs*
The "God" word is really just a con artist's prop, unless the theist can be made to specify at the outset
exactly how they define the term, in a way that doesn't let them use it as Silly Putty. This is one of the reasons I almost always use "Yahweh" instead of "God" in my posts. Yahweh (or Allah, or Sita, etc.) is is much harder to shape-shift in this manner.