A bit about the author
Richard Dawkins has authored many popular science books, especially about biology and the theory of Evolution. He's also one of the most vocal atheist voices around today. Some of his books contain numerous mentions of religion, largely because it is religious fundamentalists who oppose the theory of evolution. Many of his books explain Darwinian concepts and biology in a way that most readers can understand.
One of the books he authored was The Blind Watchmaker. The book could be seen as "Evolution/Natural selection definitively explained to layfolk." The title of the book comes from the idea that when you see a watch, you know it had a designer because it's such a complex object. Ergo, life must have had a similar designer because life, too, is so complex. So the argument goes, natural selection is just "chance" and would be like a "blind watchmaker." Dawkins sought to destroy that misconception about natural selection. According to Dawkins, a frequent (straw man) argument lobbied against natural selection is that one wouldn't expect a hurricane to sweep through a junkyard and assemble a Boeing 747; likewise with chemical compounds randomly reacting and forming, say, a human, or even an amoeba. However, natural processes might favor the survival and replication of certain compounds, allowing simpler compounds to grow more and more complex, and eventually evolving into life (hence, complexity arises from simplicity). One of the overarching arguments in the book was that God is not a necessary force in the development of life, a point made very clear throughout the book.
The God Delusion could be seen as perhaps a spiritual continuation of many of his earlier books, synthesizing some of the bigger concepts and explanations (especially from The Selfish Gene and The Blind Watchmaker) to ultimately denounce religion as not only unnecessary, but harmful to society. The book is aimed largely at atheists, and those who (as he says in the preface) don't realize that "atheism is an option."
The God Hypothesis and why it's wrong
One of the things Dawkins does at the outset is distinguish between religiosity, which can be seen in Einstein's views about the world, and religion, which he defines as the belief in a supernatural being or beings. The number and the nature of this being or these beings is irrelevant. What he actually does is formulate this as a hypothesis about the world, the "God Hypothesis":
There exists a supernatural, superhuman intelligence who deliberately designed and created the universe and everything in it, including us.
Though it's not falsifiable
in the Popperian
sense, it is a statement about the world, which we could theoretically find evidence for (for example: God comes down and says "HEY, HERE I AM!
" to everyone).
Dawkins systematically goes through many of the famous (and infamous) proofs of God's existence and points out the flaws in the argument. Even though doing so doesn't disprove God's existence, it at least addresses many of the reasons people believe that it is NECESSARY for God to exist (albeit, not the reasons for which people may WANT him to exist). "Arguments from Personal Experience" he attributes to various psychological phenomenon (albeit, he doesn't give much of an explanation for The Miracle of the Sun; I found one later on Wikipedia).
He then argues that God "Almost certainly does not exist" because it would be improbable, making an argument from Occam's razor effectively. Long story short, we know how to explain most things in the world, or know a method for explaining what we don't know. He gives some speculations about knowledge which science has yet to make an accepted theory for (e.g. how the universe began). With sufficiently powerful explanations, at least in theory, if God existed, where would he fit in? Why would the universe need him? And, of course, "who designed the designer"?
Why is there religion? What about morality?
Some of the strongest and most interesting arguments in the book dealt with why religion even exists, and how we can have morality without religion.
For explaining why religion persists in cultures, almost ubiquitously, today, he considers the question in Darwinian terms. Yet instead of belief in religion being a trait favored by natural selection, religion is the by-product of some other trait of humans that natural selection favored. Religion just sort of spawned and grabbed on for the ride.
For example, natural selection might favor individuals who listen to and believe their elders at a very young age. Parents give their kids important instructions like "Don't go swimming in the crocodile infested waters" and "Don't eat this particular kind of red berry, it's poisonous." Of course, the catch is that there may not be a "filter" for good ideas and bad ideas. Children would also believe "You must sacrifice a goat to the rain god on every full moon so there isn't a drought." Being far from beneficial, this is just a waste of a goat.
He also considers religion in terms of very basic meme theory (e.g. does religion have ideas which "perpetuate" its own survival?) There are some interesting ideas here: for example, the idea of immortality after death is (obviously) appealing. Add it to the vehicle of religion, and it easily stays with a people.
Dawkins attributes the origin of religion to various psychological aspects of our mind which were clearly helpful for survival. For one, we have a "dualistic mind" in that we tend to think of a division between our physical selves (the body, brain, &c.) and our actual "self," our "consciousness" if you will. Such a mentality gives rise to free will, but also facilitates the idea of a soul, obviously.
Likewise, we usually subconsciously have three modes of thinking about things: the "physical stance" (how does something work?), the "design stance" (what is the purpose of this thing?), and the "intentional stance" (what does this thing intend to do?). These modes helped our ancestors sort objects in the physical world very quickly, even if they may have been, say, a "scientifically incorrect" way of thinking about something (for example: This stick is made for hitting things. this fruit is designed for being eaten. These feet are made for running.) Perhaps, then, a natural byproduct of this is using the "design stance" on things in nature; and thus, there must be a designer. So while such psychological traits are beneficial to social interaction and survival and so on, they can foster some "bogus" ideas.
And finally, the question of morality. He cites some interesting case studies which showed that, broadly, most humans have the same morality and would make similar decisions in most circumstances. The case studies gave a group of people a situation, and asked if a particular decision was "Obligatory," "Permissible," or "Not Permissible." For example, two spins on the dilemma were: a woman sees a trolley with five people on it, and the tracks lead for a cliff. She can pull a switch and the trolley will take a different path to safety, but on this alternate path is a man who is stuck to the tracks. Most people (90-something percent) considering saving the five people in exchange for the one man to be "permissible." In a similar situation, only a large weight could stop the trolley from killing the five. The only large weight in sight, though, is an obese man away from the tracks. The decision was whether she should force the man (against his will) to stop the trolley, and most people considered this "not permissible." When similar questions were posed to other groups (including to some African tribes, only the questions were reformulated in more locally understandable situations), they had mostly similar agreements.
The idea here is that basic morality could easily come from natural selection, since moral behavior seems to cross cultures. Hence religion is not needed to act as a moral guide. (More often than not, Dawkins argues, religion provides a lot of extraneous morals which foster "Benefit our group, damn all others." However such mentalities can change over time as social interaction between groups becomes more beneficial to survival).
What about the human need or desire for god?
Dawkins answers that question by saying that even though we may want God to exist (perhaps as consolation that we'll live on after death, or acting as a personal "best friend," or whatever), it doesn't make it any more likely that he actually does. Likewise, he discusses numerous other outlets for finding such consolation (noting, of course, that most atheists find themselves comfortable with the idea of dying. One might argue, they find life more precious because they know this is the only life they have).
Finally, the argument that God and religion have served as the inspiration for art and music and so on, he dismisses with a very moving, "OMG Isn't the world so beautiful and epic through the eyes of science?" type of piece (a la Sagan). It's basically a rhetorical appeal to how science adds to the beauty of nature by letting us see behind the mystery of it all.
For the most part, Dawkins' arguments are very well reasoned, scientific, and in a lot of cases, interesting lines of thought. Atheists would probably enjoy it. However, he does make numerous snarky remarks about religion (as should be expected from Dawkins' endearingly pompous personality). Likewise, he sometimes comes off as a "bitter old atheist" near the end. But even so, I would still highly recommend this book. If not for anything else, it has a very interesting interpretation of religion from a Darwinian perspective. If you're religious, but think you can take a few punches (or agnostic, or questioning), definitely consider this book.