This is typical conventional wisdom these days: “Atheists tend more intelligent than religious people because they are able to rise above the natural instinct to believe in a god or gods, scientists have said.”
I once understood this to be true also. After all, there's much positive self-regard to being so intelligent in the secular world. Like most in this sophisticated tribe, I believed reason trumps unreasoning.
But during the western Enlightenment, reason became more limited than originally intended. Kant said we can't know the thing-in-itself, so he made reason all about epistemology in a narrow sense. Reason was no longer rooted in ontology, and anything beyond its boundaries were seen as speculative belief (or an unreasoned faith).
This view is quite contrary to John Henry Newman's quote that “Faith is a reasoning of a religious mind.”
The atheist would most likely retort: “that's the problem: the religious mind is less than adequate.”
And yet, Newman was pointing to a mind that was not dogmatic, but more integrated and whole. Behind all the tools and machinations we do with the mind, there is a pure, unencumbered intelligence (also known as nous) that is in accord with reason, and more than reason. Micheal Polanyi would also call it a tacit knowing.
We can be presented with all the facts about something, but at some point we need to make a choice about things that can't be supported purely by facts. And if we are really thinking and non-thinking for ourselves (as opposed to being indoctrinated), we will eventually intuit something more than pure reason can offer. This deeper unveiling that leads to a choice, is not opposed to reason, but a trusting response to its revelation. We found faith.
It doesn't necessarily mean faith will point us to the Truth, as it can be quite incomplete and distorted. Let's not forget that human psychology is rather complicated. As such, it ultimately depends how awake, coherent, and conforming we are to all the dimensions of the nous. For some, it is latent and for others not so much. While faith can influence our reasoning, reasoning alone will not give us authentic faith.
In a sort of irony, some recent reasoned research is confirming the limits to reason. I'm currently reading this great book by Jonathan Haidt, where he notes that French cognitive scientists reviewed the vast research literature on motivated reasoning. They concluded, “skilled arguers ... are not after the truth but after arguments supporting their views.” Without the privilege of such research, just a few hundred years earlier Jonathan Swift said, “reasoning will never make a man correct of an ill opinion, which by reason he never acquired.”
The western Enlightenment's version of reason makes no room for the things we know more than we can say reasonably. Such influences also include our sentiments, observations, experience, traditions, imagination, and instincts. While reason can refine our views, we are often rooted in the leaps we make beyond (or below) it.
Either intelligence is in principle unlimited, or else it is arbitrary, relative, and illusory, incapable of saying anything with certitude. But the shallow contemporary thinker wants it both ways: the omnipotent ability to know where to place an absolute line between what is knowable and what is not. — Robert Godwin