by definition of what God is used to represent.
if God means the highest level of All things, all knowledge, all energy, all events, all laws,
and/or the creation/cause of all these things,
then this goes beyond man's finite physical perception into a higher level beyond what
we can PROVE is in our IMMEDIATE physical world.
The minute something is beyond our IMMEDIATE empirical perception,
it is outside the physical level and on a level of abstract perception.
Well just don't expect any thinking person to swallow what you are trying to sell reverend.
A particular standard of evidence is required to prove any claim. Since godÂ’s existence is an extraordinary claim, perhaps the most extraordinary claim, proving it requires equally extraordinary evidence.
The standard of evidence required to prove a god’s existence is immediately more than any personal anecdote, witness testimony, ancient book or reported miracle – none of which can be considered extraordinarily reliable. The human mind is also highly susceptible to being fooled and even fooling itself. One could be suffering from an hallucination or a form of undiagnosed schizophrenia, hysteria or psychosis, ruling out even our own senses as reliable evidence gathering mechanisms in this case. As strange as it sounds, misunderstood aliens might even be attempting to interact with us using extremely advanced technology. In fact, reality itself could be a computer simulation which we unknowingly inhabit.
Every conceivable argument, every imaginable piece of evidence for god is not without some fatal flaw or more likely explanation which precludes it from being used as definitive proof.
There is, however, a simple answer to the question what proof would an atheist accept and the answer is: God is what it would take to convince an atheist. An omniscient god would know the exact standard of evidence required to convince any atheist of its existence and, being omnipotent, it would also be able to immediately produce this evidence. If it wanted to, a god could conceivably change the brain chemistry of any individual in order to compel them to believe. It could even restructure the entire universe in such a way as to make non-belief impossible.
In short, a god actually proving its own existence is what would convince any atheist of said godÂ’s existence.