When it comes to social progress — hang on, where are my scare quotes? — social "progress" — that's better. Anyway, when it comes to it, Britain and America often wind up at similar destinations but by two very different routes. In the US, big changes — on abortion, gay marriage — are ushered in by judges claiming to have discovered a hitherto unknown right to them lurking in the "emanations" of the "penumbra" of the constitution: the "right to privacy", for example, under which abortion was legalised coast to coast. In Britain, everything's much more incremental and utilitarian: there...