Everybody has that wonderful feeling of "I'm certain this is true." Everybody. I blogged about this neuroscientific fact in I know I'm right about uncertainty.
I included an Amazon summary of "On Being Certain: Believing You are Right Even When You're Not."
You recognize when you know something for certain, right? You "know" the sky is blue, or that the traffic light had turned green, or where you were on the morning of September 11, 2001--you know these things, well, because you just do.
In On Being Certain, neurologist Robert Burton challenges the notions of how we think about what we know. He shows that the feeling of certainty we have when we "know" something comes from sources beyond our control and knowledge. In fact, certainty is a mental sensation, rather than evidence of fact.
Because this "feeling of knowing" seems like confirmation of knowledge, we tend to think of it as a product of reason. But an increasing body of evidence suggests that feelings such as certainty stem from primitive areas of the brain, and are independent of active, conscious reflection and reasoning. The feeling of knowing happens to us; we cannot make it happen.
This is the source of religious faith: primitive areas in the brain. Evolution apparently has selected for feelings of certainty. Which makes sense.
Could be a tiger in the bushes... or maybe not... could be a rabbit... not sure what to do... maybe wait and see what emerges..., anyone who carries around that gene in prehistoric days probably wasn't going to live long enough to reproduce.
Doing something confidently, even if it's wrong, seems to be a better recipe for survival. So a feeling of certainty in the absence of conclusive evidence is part of being human.
Religions, though, elevate this commonplace sensation into a divine virtue: faith. Now, though, certainty is applied to a supernatural realm where God and other invisible entities are believed to exist.
The brain's Certainty Producing Machine cranks up a pleasurable feeling of "i'm right because I feel that I'm right, and that's all there is to it. I know God exists. Don't ask me why. There's no why. I just know it. For sure."
Lack of evidence? No problem. Here's how Julian Baggini describes the belief delusion in his nicely-argued little book, Atheism: A Very Short Introduction.
As a matter of fact, it seems that most religious believers justify their faith by an inner conviction. As Russell Stannard said, for the believer, it is as though they know God exists and no further arguments are required.
...Grounding religious belief in this kind of conviction, which feels to the believer like the direct apprehension of absolute truth, can utterly negate the power of all the arguments for atheism I have advanced so far. We can compare this to the force of argument against the existence of the self.
...Skepticism dissolves when confronted with the phenomenological certainty -- the indubitable feeling -- of our own existence. For many religious believers, their belief in God's existence is of comparable strength. They feel the truth of God's existence so strongly that they can no more doubt it than they can doubt the existence of their own selves.
...I would, however, say two things about this which are of interest to believers who are prepared to at least question their convictions and to atheists striving to understand religious belief.
The first is that we should be very careful about what we say cannot be doubted. 'Cannot be doubted' can really mean 'don't want to doubt' or 'cannot imagine the thing being doubted not being true.'
It may seem to the religious that they can no more doubt God's existence than their own, but this cannot be universally true, since plenty of people lose their belief in God and yet no psychologically healthy person loses her belief in herself (although plenty, after philosophical reflection, lose their belief in what they thought the self was.)
To those who say they cannot imagine the possibility of God not existing, I say try a little harder. Imagine what it is like for atheists. You must be able to see that they can not only live, but live with purpose and values. Try and imagine what it is like for such a person to live without God, and then try and imagine yourself living such a life.
The second point is to recognize that this reliance on faith -- an inner conviction which is not based on reason or evidence but is seen as a source of knowledge -- has to be viewed honestly as a risky strategy. What needs to be acknowledged is that around the world people have the same kind of conviction but with very different specific content.
As an extreme example, people have felt convinced that God was calling them to commit acts such as the 11 September 2001 attacks on the United States. On a more everyday level, people tend to understand the God they feel the presence of in terms of the image of God presented to them by their local religion.
People in Muslim countries, for instance, do not feel the presence of Jesus. Indeed, even within Christian cultures, what people report to know the existence of changes over time and across denominations.
...For many atheists, the mere fact that people use the same grounds -- personal conviction -- to justify belief in different, incompatible religions is enough to show that such convictions cannot be the proper basis for religious belief. This is because these convictions support all religions equally, yet not all can be true.