Yet it was not in the 19th but in the 20th century that the mythology of decline really took hold. The era of the world wars and the Cold War, which witnessed the rise and fall of Mussolini's Roman Empire, Hitler's thousand-year Reich and Lenin's dictatorship of the proletariat, was bound to generate theories of decline. But the most influential of them all was the one that embraced "the West", a concept that was just becoming fashionable as the European empires reached their zenith in the years before 1914. Exactly a century ago, an obscure Prussian schoolmaster by the name of Oswald Spengler had a revelation. 1911 was the year of the Agadir crisis, the Kaiser's clumsy attempt to emulate Bismarck's Ems telegram, the ingenious ruse that had tempted Napoleon III into the Franco-Prussian War. Agadir was the crisis that gave "gunboat diplomacy" its name. It turned out badly for the Germans and especially for the Kaiser, who lost his nerve and with it his influence over the political and military elite, who would take matters into their own hands three years later after the assassination at Sarajevo, with catastrophic consequences not only for Germany but for Western civilisation. (It is curious that Israel's enemies —Iran, Egypt and Turkey — have all been playing at gunboat diplomacy lately, sending warships through the Suez Canal or threatening to break the naval blockade of Gaza. My guess is that they will back down as soon as they encounter firm resistance, just as the dispatch of the German gunboat Panther to Agadir, which forced the French and British to react forcefully, ended in humiliation for the Kaiser and his High Seas Fleet.)

The spectacle of that humiliation, however, prompted intimations of civilisational mortality in Spengler. Two decades later, on the eve of Hitler's seizure of power, Spengler looked back on that moment when his big idea came to him: 

I was disgusted by the idiocy of our policy, which calmly acquiesced in the completion of the encirclement of Germany, by the blindness of all the elites that did not believe in a war that in reality had already broken out, by the criminal and suicidal optimism, which boasted of our rise since 1870, our assumed but in reality long since squandered power base, our seeming wealth, which was actually only for the shop window, and which dismissed any notion that all this might fundamentally change. And behind this I saw the unavoidable revolution, which both Metternich and Bismarck had clearly foreseen, and had to come and not only for Germany, whether or not we came home victorious. 

He saw Marx as an Englishman and Marxism as a perversion of Manchester (what we would call free-market) liberalism. This would have surprised Marx as much as his critics, but perhaps Spengler was on to something: the evolution of China into a market economy run by a one-party state, still based on the dictatorship of the proletariat, shows that Marxism is in an important sense ideologically parasitical on capitalism. Only the free market can generate the wealth necessary to sustain a party apparatus and its sprawling system of political patronage. It makes little difference whether the party in question calls itself Communist, fascist or national socialist: in all three cases, the party has a monopoly on access to the market which enables it to enrich its leaders and enforce obedience from capitalists. Spengler himself favoured what he called "Prussianism" (Preussentum), an idealised version of Frederick the Great's enlightened despotism. As Frederick's favourite philosopher Voltaire remarked, Prussia was "Sparta in the morning and Athens in the afternoon". But as Voltaire discovered when he fell from grace, "Old Fritz" was in practice more despotic than enlightened. That is why his militaristic brand of absolutism appealed so much to Carlyle, to Spengler and to Hitler. 

Seven years and one world war after Spengler's premonition, his book appeared in 1918, just in time for the dissolution of the German Empire. Der Untergang des Abendlandes was translated as The Decline of the West, but the German word Untergang is much more drastic than "decline": something like "downfall" would be closer. It was an apocalyptic vision for an apocalyptic time. Yet the war itself does not figure in the book, even indirectly. Spengler's "morphological" method, which he claimed to have taken from Goethe, treated civilisations as organisms. Western civilisation had long since passed its creative zenith and, like others before it, had now entered an era of "Caesars" —empire-builders such as Cecil Rhodes, for whom Spengler harboured boundless admiration. Spengler was an extreme historicist, i.e. historical relativist: he believed that Western science, philosophy and art (not to mention religion and morality) had no objective validity, but merely expressed the peculiar products of our time and place, the ephemera of a transient culture already in the grip of dissolution.

Spengler is no longer much read today, but the influence of his mythology of decline persists. Take, for example, the eminent sociologist Robert Bellah's new book, Religion in Human Evolution: From the Paleolithic to the Axial Age. This is a work of comparable range to The Decline of the West, and its scholarship is indubitably sounder. Indeed, such luminaries as Jüergen Habermas and Charles Taylor enthused about Bellah's magnum opus, which has been hailed as the greatest contribution to the sociology of religion since Max Weber a century ago. Yet Bellah's conclusion is pure Spengler: "If there is one primary practical intent in a work like this that deals with the broadest sweep of biological and cultural evolution, it is that the hour is late: it is imperative that humans wake up to what is happening and take the necessarily dramatic steps that are so clearly needed but also at present so clearly ignored by the powers of this earth." For Bellah, then, the threat of climate change serves the same function that the threat of world war did for Spengler. Bellah also shares Spengler's historicism, only with an anti-Western bias: "To assume that ‘we', particularly if we mean by that the modern West, have universal truths based on revelation, philosophy, or science that we can enforce on others, is the ideological aspect of racism, imperialism, and colonialism."