Between them the Arab Spring and Boko Haram of northern Nigeria are doing a good job of putting Sharia law on the map. These two extremes in fact show dramatically how Sharia interpretations can vary from destructive madness as in Nigeria to calm accommodation, even liberalism, as in Tunisia. Sharia law is not only a legacy of Mohammed – he only devoted a handful of pages in the Koran to the dos and don’ts of moral life. Much comes from the Hadith, the collection of thoughts and sayings from the first couple of centuries after Mohammed’s death. Much of the Hadith is even more remote from the central text and Mohammed than some of the reflections of St Paul and the final chapter of the New Testament, the Apocalypse of John, are from Jesus and the Gospels. Boko Haram, with its bombings, appears to be causing mayhem, drawing support in...