Do atheists and theists agree that it is impossible to decide whether or not God exists? I would suggest that the answer is emphatically No. A consensus can be reached as follows:
Atheists know what God is (imaginary) but theists do not (inexplicable supernatural) which is the opposite of what you would expect.
Scientific research about the mind and God strongly suggests that our conception of God is personal, reflects or own prejudices and although it is irrational, it persists because it is reinforced in churches by people who think like us and support us. But it is impossible to reconcile the diversity of human beings and their cultures, each of which is right in their own belief with the prevailing concept/s of a single God. We cannot all simultaneously disagree on principles and be right about them. Consequently, one of two things must be true.
The first part: God/Gods exist but our conception of Him/Them is false
OR the second part: No Gods exist.
Most theists and all atheists (that's nearly everyone) agree that many Gods do not exist. Church dogma is inflexible and cannot adapt to new data therefore ruling out by fiat, the possibility that the nature of God is mistaken. Therefore (by consensus if not proof we dismiss the first part (above)) and are left to conclude that no God exists.
Having reached this conclusion we can now explain the whole of the natural world including the image of God that exists in out imagination. And be comforted by the thought that although we all die, we are never dead. (I do not mean that we survive our own death, just that you can never correctly utter the words "I am dead.")
The only excuse for not accepting this consensus is lack of education - and that is not an excuse.
I wish to add that it is important to appreciate what is going on when a religious faction insists that they and they alone hold the correct view of a certain matter, the sort that leads to the notion that the in-group adherents are saved and going to heaven, while all the others are sinners bound for hell.
If several such groups can co-exist an external observer can see symmetry in the situation while the in-group adherent is exposed to amplification of a particular view and therefore the symmetry is lost in his reference frame.
This amplification means that the consensus argument is less apparent or even invisible to in-group adherents.
"Do atheists and theists agree that it is impossible to decide whether or not God exists?"
We can't even agree that we don't agree.. I was often told that subconsciously i am actually a believer and at some point in my life i will turn "back" to Jesus or Allah or the easter bunny's evil twin.. or something among those lines.
An atheist doesn't need to prove it, for us its enough to not believe it.
For a theist to prove that god exists he would have to KNOW that a god exists, but they are called believers because they don't know it, they just believe it. Yet they don't say "i don't know if god exists but i believe he does" most of them say "i know god exists, my proof is that the bible says it" or "who else did -input alleged miracle- if not god?!" etc and to back it up some often pull out the *undeniable* "and you will burn in hell/jahannam/Detroit's sewers for eternity if you don't believe it"- argument.
I can't agree with somebody who claims he knows something that he just believes.. At least not on related topics, so no, we apparently can't agree that its impossible to decide. They already decided it almost irreversibly so their brain shuts off and will ignore even obvious and undeniable proof that their teaching is disproven by itself, no need for us to add anything.
However to actually be able to be disproved, you would have to allow some input to be able to process it, and since the brain shuts off at that point it won't allow any input. They even deny facts straight from the Qur'an or Bible or the Mianus phone book (if thats where they got their belief from), because they cling to their own (often very flexible) version and not the actual teachings.
In rare cases you manage to smuggle in a tiny ray of light into the darkness but sadly, mostly it isn't enough to illuminate anything.
Also you said:
"The only excuse for not accepting this consensus is lack of education - and that is not an excuse."
Did lack or education or rationality ever stop a "true believer" or an idiot from sticking to any claim/statement no matter how absurd? Not that i knew.
ps. in THIS case i am not refering to believers as idiots althogh i am tempted.. knowing they prefere their saddistic omnipotent imaginary friend over logic reason and humanity.