campaign for Brexit. Suddenly, as the liberal thinker Michael Ignatieff recently wrote: Enlightenment humanism and rationalism can no longer adequately explain the world were living in.The largely Anglo-American intellectual assumptions forged by the cold war and its jubilant aftermath are an unreliable guide to todays chaos and so we must turn to the ideas of an earlier era of volatility. It is a moment for thinkers such as Sigmund Freud, who warned in 1915 that the primitive, savage and evil impulses of mankind have not vanished in any individual, but are simply waiting for the opportunity to show themselves again. Certainly, the current conflagration has brought to the surface what Friedrich Nietzsche called ressentiment a whole tremulous realm of subterranean revenge, inexhaustible and insatiable in outbursts.By contrast, the fundamental premise of our existing intellectual frameworks is the assumption that humans are essentially rational and motivated by the pursuit of their own interests; that they principally act to maximise personal happiness, rather than on the basis of fear, envy or resentment.Trump, Brexit and the age of popular revolt: 2016 in Long Reads Read moreThe bestseller Freakonomics is a perfect text of our time in its belief that incentives are the cornerstone of modern life, and the key to solving just about any riddle. From this view, the current crisis is an irruption of the irrational and confusion and bewilderment are widespread among political, business and media elites. The ordinarily stolid Economist has lately lurched from dubious indignation over post-Truth politics to the Rip Van Winkle-ish declaration of The New Nationalism. Many other mainstream periodicals now read like parodies of New Left Review, as they attend belatedly to the failings of global capitalism most egregiously, its failure to fulfil its own promise of general prosperity.We can now see, all too clearly, a widening abyss of race, class and education in Britain and the US. But as explanations proliferate, how it might be bridged is more unclear than ever. Well-worn pairs of rhetorical opposites, often corresponding to the bitter divisions in our societies, have once again been put to work: progressive v reactionary, open v closed, liberalism v fascism, rational v irrational. But as a polarised intellectual industry plays catch-up with fast-moving events that it completely failed to anticipate, it is hard to avoid the suspicion that our search for rational political explanations for the current disorder is doomed. All of the opponents of the new irrationalism whether left, centre, or right are united by the presumption that individuals are rational actors, motivated by material self-interest, enraged when their desires are thwarted, and, therefore, likely to be appeased by their fulfilment.This notion of human motivation deepened during the Enlightenment, whose leading thinkers, despising tradition and religion, sought to replace them with the human capacity to rationally identify individual and collective interests. The dream of the late 18th century, to rebuild the world along secular and rational lines, was further elaborated in the 19th century by the utilitarian theorists of the greatest happiness for the greatest number of people and this notion of progress was embraced