What can make tens of millions of people -- who are in their daily lives peaceful and compassionate and caring -- suddenly want to physically dismember a man for drawing a cartoon, or make excuses for an international criminal conspiracy to protect child-rapists?
Not reason. Not evidence. No.
But it can happen when people choose their polar opposite -- religion. In the past week we have seen two examples of how people can begin to behave in bizarre ways when they decide it is a good thing to abandon any commitment to fact and instead act on faith.
It has led some to regard people accused of the attempted murders of the Mohammad cartoonists as victims, and to demand "respect" for the Pope, when he should be in a police station being quizzed about his Church's role in the past in covering up the rape of children.
In 2005, 12 men in a small secular European democracy decided to draw a quasi-mythical figure who had been dead for 1400 years. They were trying to make a point. They knew that in many Muslim cultures, it is considered offensive to draw Mohammad.
But they have a culture too -- a European culture that believes it is important to be allowed to mock and ridicule religion. It is because Europeans have been doing this for centuries now that we can no longer be tyrannised into feeling bad about perfectly natural impulses.
Some of the cartoons were witty. Some were stupid. If you disagree with the drawings, you should write a letter, or draw a better cartoon, this time mocking the cartoonists. But some people did not react this way.
Instead, Islamist plots to hunt the artists down and slaughter them began. One otherwise liberal newspaper ran an article saying that the cartoonists had engaged in an "aggressive act" and shown "prejudice... against religion per se".
Let's state some principles that -- if religion wasn't involved -- would be so obvious it would seem ludicrous to have to say them out loud.
Drawing a cartoon is not an act of aggression. Trying to kill somebody with an axe is. Yet we have to say this because we have allowed religious people to claim their ideas belong to a different, exalted category, and it is abusive or violent merely to verbally question them.
This enforced "respect" soon extends beyond religious ideas to institutions. It is indisputable that the Catholic Church systematically covered up the rape of children across the globe, and knowingly put paedophiles in charge of more kids. Joseph Ratzinger -- who claims to be "infallible" -- is the head of this Church.
By 1962, it was becoming clear to the Vatican that a significant number of its priests were raping children. Rather than root it out, they issued a secret order called "Crimen Sollicitationis"' ordering bishops to swear the victims to secrecy and move the offending priest on to another parish.
Imagine if this happened at your company. Imagine you discover there was a paedophile ring running your creche, and the company boss issued a stern order that it should be investigated internally with "the strictest secrecy". You would both -- rightly -- go to prison. Yet because the word "religion" is whispered, the rules change.
If you can't bear to hear your religious figures criticised, a sane society should have only one sentence for you. Tell it to the judge.