Answer by Sabarish Bharadwaj:
Actually, you can prove the non-existence of deities, depending on how they are defined.
For instance, suppose I define a god 'Airakea', and claim that she instantly turns any person into Hulk (green colored, super-human strength, etc.) when he/she kicks a kitten. No other conditions apply. You kick a kitten, you get freakishly strong, simple as that.
Now, would you say it is impossible to prove that 'Airakea' does not exist? No. You just go kick a kitten and see if you turn into Hulk. If you don't, then Airakea doesn't exist.
You can do that with any god- if the god is properly defined with testable claims, then you can easily verify its existence. One must wonder, is it just coincidence that almost all gods deal with 'sinners' in the afterlife, but never manage to strike someone down whenever they blaspheme?