Ok, so is it rational to say/believe: No gods exist.
If it's not, is it rational to say/believe: No pink unicorns exist.
Is it rational to say / believe: ESP does not exist?
And for all three beliefs, if new evidence would emerge that suggests otherwise, then one's nonbelief would appropriately be re-examined.
To expand on what I just posted in response to Huh-What:
All three of those statements are the end state of a logical process. What we need to do is go back and figure out the root cause of those statements.
Let's pick on the "no pink unicorns" one.
I believe no pink unicorns exist.
Why do I believe that? Because I have never been exposed to any evidence that they exist.
What would constitute evidence of a pink unicorn? For me, it would be visual and tactile sensory input corresponding to the characteristics of a pink unicorn: a four-legged mammal, between the size of a small goat and a large horse, with naturally pink fur and a single straight horn growing naturally out of its forehead.
I have very clear, concise, objective expectations when it comes to evidence confirming contact with a pink unicorn.
Same with ESP. To me, evidence of ESP would be someone passing a carefully designed test, probably involving a safe deposit box.
But what about God?
What constitutes evidence of God?
Most people balk at this question, or they come back with an answer that they can be easily talked out of. "But a magician could do that" or "but that could happen by random chance" are good counterarguments to a lot of things that people consider evidence.
It's a hard question to answer.
But without coming up with an answer to it, I would say no, it is
not rational to say / believe "no gods exist".