Two new books, Mark Lilla’s The Stillborn God and Lee Harris’s The Suicide of Reason, argue that religious extremism imperils the liberal – and, as they see it, fragile – traditions of the West. Both books base much of their analysis on the writings of Thomas Hobbes, the seventeenth-century English philosopher of public order. But they see the extremist danger coming from dramatically different religious directions. For Lilla, it radiates from unresolved tensions in Christianity, which can burst forth at any moment into millenarian madness. Harris, on the other hand, sees the threat coming from an Islamic fanaticism that the rationalist West is unable to comprehend, much less counter. Matthias Kuntzel shares Harris’s fears. His Jihad and Jew-Hatred is a compelling historical account of how modern Islamic extremism has been informed by the anti-Semitism of the Third Reich.