At its heart, this book is about the difference between faith and reason. Faith is blind. It is not based on evidence or reason, and therefore offering evidence or reasons will not shake the faithful from their beliefs. Harris thinks that is very, very dangerous. It will come as no surprise to anyone that he began writing this book on September 12, 2001.
Harris argues that relying on faith instead of reason is a bad way to lead your life. It leads to all sorts of weird and dangerous beliefs, prevents important scientific discoveries, and stirs hatred between people who hold mutually inconsistent faith-based beliefs. Of course, people make mistakes when they rely on evidence and reason, but at least if we rely on reason and evidence, we are moving in the right direction and we are open to changing our minds when we are wrong. If our beliefs are based on faith, we are stuck forever.
This book will make religious people uncomfortable. Harris says exactly what he thinks, without making an attempt to spare the feelings of the religious. He does not, however, call anyone names or say anything in order to be mean or offensive. He simply states that facts as he sees them.
Some reviewers claim that Harris is "intolerant" or a "fundamentalist." They are wrong. Harris, unlike many religious leaders, fully supports the right to think, say and believe as you wish. He opposes any form of oppression. On other hand, Harris also reserves the right to think some beliefs are foolish. You probably do not respect the belief that Elvis is alive. Harris feels the same way about religious beliefs. He certainly would not want to see Elvis believers put in jail or denied rights, but he feels free to say that belief in Elvis is just plain wrong.