Does atheism guarantee disbelief in anything unproven?

[Tempus]

While atheists seem to tend toward being smarter, more rational people, there's nothing that guarantees that each individual will be.

The rejection of the man-made concept of god is not a sufficient condition for intellectual or moral emancipation. Atheists have no right to go around looking superior. They have only fulfilled the necessary condition by throwing off the infancy of the species and disclaiming a special place in the natural scheme.

--Christopher Hitchens (Introduction to The Portable Atheist)

Sounds like a good premise for a scientific study. Defining the parameters would be highly subjective. On second thought your opinion does not appear to be falsifiable.

Just to be clear, I wasn't suggesting being an atheist automatically makes you smarter, merely that atheism has been correlated to higher levels of intelligence. There's been at least a few studies done on the subject. Still, as I said before, there's no reason why there wouldn't be stupid atheists. There's stupid people of every persuasion.

I would speculate that the causes of (or perhaps it's better to say 'the significant contributor to') a person's high intelligence and their atheism is a questioning attitude. Someone who is inquisitive about the world and themselves / their own beliefs will become more intelligent than someone with a dogmatic belief structure because they'll change and modify incorrect beliefs where the dogmatist won't. This would make inquisitiveness the root cause of atheism and higher-intelligence. But again, that's just speculation.