The End of Faith by Sam Harris (2004) is a disturbing and important book. It's a basic tenet of nearly every religion that "ours" is certainly the true faith, while "theirs" is at best wrong, and at worst a threat to people of the "right" religion. What action one may take on the basis of this certainty varies considerably over time and between religions. Many religions coexist peacefully with others, while some label non-believers as "enemies of God" who are worthy of discrimination, abuse, and even torture and death. Examples abound, from the Inquisition to the Salem Witch Trials to the 9/11 attacks and daily suicide bombings in Iraq.-The End of Faith (page 134)
Harris argues that with the modern availability of "user friendly" weapons of local and even mass destruction, faith itself has become a danger. This does not apply only to Islam (the obvious modern example of the dangers of certainty). Religious based "reasoning" and influence on government leaders threatens scientific education and potentially life-saving medical research even in the U.S., where religious freedom allows one to follow the religion of one's choice (or more likely one's parents' choice), but where it is politically unwise to question the importance of some sort of religious faith, or to suggest that religious faith itself is dangerous.
Terrorism by Islamic "extremists" is the most dangerous example of faith run amok. The strange thing is, the extremists are not all that extreme. They are pretty much going by the book, truly doing what they believe to be best for their people, their God, and themselves (as martyrs, immediately bound for paradise). As Harris says,
The men who committed the atrocities of September 11 were certainly not "cowards," as they were repeatedly described in the Western media, nor were they lunatics in any ordinary sense. They were men of faith - perfect faith, as it turns out - and this, it must finally be acknowledged, is a terrible thing to be.Amen. Please read this book.