David Cameron calls Isil an “existential threat” to the Western way of life. On the face of it, that seems ridiculous. How could a bunch of relatively poor, ill-armed fanatics and psychopaths conceivably topple what remains the most dominant civilisation since the Roman Empire?
In physical terms, they can’t (yet). We in the West have much more money, many more weapons (though here in Britain, we have been doing our best to weaken ourselves militarily) and greatly superior technology. While Islamist fanatics can murder 30 British tourists on a North African beach, we can probably intercept enough of them here to keep their activities below a certain level.