This is an excerpt from Lee Harris's The Suicide of Reason: Radical Islam’s Threat to the West posted by Richard Landes at Augean Stables.
Both the tribal mind and fanaticism are rational adaptations to a world ruled by the Law of the Jungle – rational in the sense that they increase the odds of surviving. On the other hand, the rational actor doesn’t have a chance of survival in the jumgle. He who has neither tribe nor pack to defend him will perish. That is why the rational actor must be horrified at the very thought of a return to the Law of the Jungle – in order to exist at all, the rational actor must be living in an environment in which the Rule of Law has replaced the Law of the Jungle. Yet in the modern liberal West, the Rule of Law has been so successful in pushing back the jungle that many in the West have forgotten that we are the exceptions, and no the rule.
In short, today there are two great threats facing the survival of the modern liberal West. The first is its exaggerated confidence in the power of reason to alter the human condition; the second is its profound underestimation of the power of fanaticism to change the world.
Paul Berman's Terror and Liberalism makes the same point. Which needs making again and again.