As an atheist, it is easy to view those with traditional religious beliefs in a condescending manner. We atheists are very bright, scientific, rigorous, and advanced; those who believe in silly things like god(s) are primitive, dumb, and bigoted! Or so We like to tell ourselves.
However, the relatively new field of cognitive anthropology has shown this view to be absolutely false. Most works in this field are turgid, slow moving, and difficult. (cf. works by Scott Atran and Pascal Boyer) This book is not. It is terse, to the point, and lucid. All jargon is explained in the text and it contains a glossary so you can refresh your memory if need be.
Barrett's basic idea is that our minds have evolved in a way that makes religious belief natural. It is so natural because it fits nicely with many unreflective beliefs that our mind has. For example, all people have mental equipment which makes them hypersensitive to detecting agency, they also have mental equipment which makes them view other things as having minds.
On top of this, people have intuitive moral concerns that are universal. Therefore, they easily view these morals as coming from somewhere.
In short, as a hypersocial species, humans find it quite natural to posit minimally counterintuitive God concepts. These concepts are satisfying and spread easily among others.
Here is an example of Barrett's mode of analysis.
Suppose you talked to a guy named John a few days ago. John tells you that your house is known to be haunted. He recounts some tales that were told to him by the last owners of the home. You don't really believe it, but you do tuck it away in your memory.
Now you are in your home alone at night. Suddenly the radio turns on in the other room. You get a little scared. Then you here creeks coming from the basement. Now your blood is getting hot and your palms are sweating. You don't believe in superstitious nonsense. All the same, you can't help the fear. Then you remember what John told you. What if it were true, you think to yourself.
Why does this seem so plausible?
According to Barrett this would occur for many reasons.
1) Humans gain social information from others and assume that non-interested parties are not purposefully decieving us. Therefore, John's tale is percieved as being relevant, even if it is first construed as nonsense.
2) Humans have artifact detection devices in their brains. We know that a radio is created for a specific function.
3) Humans have a hypersensitive agency detection device. We are always looking for evidence of agency, even where none exists.
4) Humans have a Theory of Mind (ToM). We are always trying to interpret things mentally. For example, my computer IS STUPID!
5) Combining 2-5, You know that your radio is turned on only when someone purposefully turns it on to listen to music. That it might turn on accidentally, or due to mechanical failure is not intuitive. Thus, your unreflective thought is: Who turned my radio on and why? If nobody is in your house, you can reflectively compensate for your intuitions, but it is tough. Once your mind starts churning, it is tough to shut off. Now that your agency detection device is working in high gear, you hear the creeking from the basement. Your mind interprets this as movement from somebody attempting to do something. After this, you remember what John told you. Think about how intuitively satisfying such implicit reasoning is! It makes sense of everything around you in a parsimonious manner. To deny this and concoct reflective explanations that deny agency and ToM requires that you get very non-intuitive. It is possible. For example, you can reason that a mechanical fluke caused the radio to turn on, and that the creeks in the basement are nothing more than the water heater. My guess is this explanation will not provide total comfort. Nor will you be certain that it is true. It is just not that intuitive. Although your reflective explanation, in this case, is almost certainly the correct one, the mind does not think so.
Why not?
Error management Theory. Suppose you are in the woods and hear a twig snap. Was it the wind or a predator? Your brain can go either way. From the point of view of natural selection, defaulting in either direction has costs and benefits. If you remain calm assuming it was the wind and are wrong, you end up as lunch. If you get nervous, assuming a predator is lurking after you, your body uses up some metabolic energy. After eons of rigorous selection, it clearly pays to error on the side of caution.
This applies, mutatis mutandis, to the haunted house. Suppose you remain calm and believe the events have been caused by non-agents- What if you are wrong? What if it is a ghost or intruder? (BTW, as Barrett explains, a haunted house is even more intuitive because we view houses as having territorial owners. If the ghost owners view you as a trespasser, that is a good reason for getting angry. Your mind intuitively knows this, thus you do not break into homes.)
EMT theory makes it more likely that you will posit the ghost or agent based explanation. My guess is that most of us would consciously believe the mechanistic explanation, since it is rational, while our bodies would believe the agent theory and fire up the fight or flight system.
It is not hard to go from this situation to Monotheism. In fact, as Barrett shows, children seem to be intuitively wired to believe in some sort of all knowing, immortal being.
I recommend this book to all theists and atheists. It is not an apologetic for belief, nor is it an atheist manifesto. It is, rather, an objective look at why so many people believe in God. For an atheist such as myself, Barrett's book gives much food for thought.
Are atheists really superior to theists? Should we discriminate against the religious? Should we try to eradicate religion?
After reading Barrett my view on these questions has changed.
However, I will let the reader draw their own conclusions from this diamond of a book.