I cannot
But why should I worry about what no one even defines?

Am I to worry about the idea in your mind, or a Muslims, a Hindus, someone else? Since those internal models do not match person to person even inside religion the term God holds no meaning other than what YOU assign to it.

I do not assign any meaning to it, instead I insist believers define it, and they universally fail.

So there is no need to be 100% certain there is no God (whatever the hell that means).

Can we be 100% certain that there are no round squares? Yes, because it creates logical contradictions. Most definitions of God have the same dilemma, though not all. So I can be 100% certain that most definitions of God do not exist.

An Agnostic is someone who believes we can't be sure there is no god. Also it is a person who does not follow an organized religion.

In it's literal sense, there is nothing that humans can be certain of. We can only be certain of anything in a practical sense.

Beg, plead, cry, for gawds help in some horrible situation...then hold yer breath!

God is just such a silly thing to argue about.

Pretty easy.

We can all agree there is no such thing as magic. Religion is pure super naturalistic magic. There is absolutely no reason, logic or true workings of the universe in it. It is totally ego centric and self-serving especially for the hierarchy. Religion goes against all the workings of the natural world and principles of the universe. How can one (albeit pretty stupid) life form be paramount in the vastness of the universe? Fear, ignorance, selfishness, greed and arrogance are the central tenants of all religions!!

Unless and until there is credible, verifiable EVIDENCE to prove the existence of any deity,
I will maintain that there are NONE.
Prove to me that there is a god, or are gods, and I'll consider changing my mind.
I am completely sure of my position. The burden of proof is always on the person who
claims something exists. I don't have to prove there is no "there" there.

I am an agnostic - anti-theist.

I'm with Penn Jellette on this:
Agnostic and atheist answer two different questions:
We cannot know fur shur how our universe started: agnostic (without knowledge)
There ain't no all powerful invisible critters fucking with humans on the earth: atheist (there is no reliable proof of such a being.)

And I agree with Sam and Christropher,... I am an anti-theist because I oppose religionists imposing their mental illness on all us good folks.

Take A Look Around You, The World.

I'm not 100% sure. I'm 99.99% sure. In other words I acknowledge that it is impossible to prove the non-existence of something.

If there was a god we allowed on this s*** that happens

What do you mean by god?

I am intrigued by “Spinoza’s god” and monist approaches to explaining consciousness but I’m pretty sure most believers, faithists, and most people in general would consider those to be atheist concepts if they took time to think about it

How can we be certain Bertrand Russell's teapot is not orbiting our unverse in some outer shell of the unverse the encapsulates the many universes one of which we live in?

The thought that there's any kind of more powerful being in this universe running things or being involved with its development is completely insane. When I think that it's true I feel insane, when I remember what it was like to believe that I was insane. End of story.

I would be careful to say I am 100% certain about anything so ambiguous

Can you be certain there isn't an invisible, untouchable monkey's ass circling all our heads? (Perhaps I should have said "unsmellable" ). Belief in god is the same thing except god has been perpetuated because power structures have an investment in the concept. But it's just as verifiable as an invisible orbiting monkey ass.

Smells like bullshit, is bullshit - that's my rationale

The keyword being "certain". We cannot prove with certainty what may not even be there. We just logically conclude that a god or gods were not necessary to get to where we are now, and therefore, for lack of evidence, they never existed.

If there is a God, I believe all the religulous have it wrong. Particularly if they are killing each other over what they believe god really is...