The diagnosis, surprisingly, is more complex than the cure. There are numerous viruses attacking the Western body politic, but only one medicine. To face the future unflinchingly, we must return to the past: listen to the patriarchs and prophets, the ancestral voices of our literature, break open the arsenal of our intellectual history, and mobilise the resources of righteous indignation against the dominions, principalities and powers of darkness that threaten to overwhelm us. The great books, from Homer to Shakespeare, from Plato to Pascal, from Dante to Bellow, must once again not only be assigned to every student, but learned where possible by heart. The music of the masters, from Gregorian chant to George Gershwin, from Sebastian Bach to James MacMillan, from Palestrina to Arvo Pärt, must not only float across the courts and quads of our colleges, but fill our airwaves and headsets. The art and architecture of the West must not only fill our galleries and screens, but be protected from the vandals who threaten antiquities from Leptis Magna to Palmyra.

In short, we must celebrate Western civilisation as the living, breathing, flourishing organism that it is. Unless the coming generations embrace its treasures and make them their own, we will forfeit all that the children of Abraham have created to give glory to God, all that has ennobled the West and enabled the rest of humanity to be more humane. But a robust, self-confident culture alone is not enough: there must also be foreign and defence policies muscular enough, not only to support the democratic, liberating and civilising mission of Western civilisation, but also to keep that civilisation safe from predators. Just as the Chinese Communists and others have embraced the market, not to dismantle their totalitarian power structures, but only to reinforce them, so they are now adopting the cultural habits and artistic tastes of the West, while ignoring the religious roots of the laws and liberties that made such a civilisation possible. And while the Islamists in general fear and abominate Western culture, or even wish to extirpate it, because they sense its power, there is always a danger that our political will may be insufficient to resist the demographic pressures now being brought to bear in Europe. I am speaking of France, in which a quarter of teenagers are already Muslims, or England, which within a generation may have followed the example of its capital. Europe’s “migration crisis” is not a crisis; it is, as Lionel Shriver aptly puts it, the new normal. One does not need to have an iota of sympathy for Donald Trump’s crude discrimination against Muslims, or even advocate the mass repatriation of illegal migrants — by the time he leaves office Barack Obama will have deported nearly three million of them, more than all other presidents since 1892 combined — to see that the numbers now entering Europe and America are impossible to integrate. If Western civilisation is to survive the mobilisation of mankind in pursuit of prosperity on a scale that dwarfs anything seen before, we shall have to restore the borders we have been striving to abolish for decades. It is not illiberal to make secure borders the quid pro quo for generous treatment of refugees. Israel, which has no choice but to keep its borders secure, is a nation of immigrants. Maybe in this respect, as in others, Jews can be a light for the Gentiles.