During the long nineteenth century 'civilization' was the highest-order concept through which European empire was imagined and justified. It divided the world into a hierarchical space of identity and difference on the basis of the idea of progress. It posited a constitutive identity among societies by assimilating them to a universal timeline of development, and a historical difference among societies by assigning them to different stages of development, and different velocities of progress, along that timeline. Modern Europe was a singular civilization at the crest of world history; other societies were shadows of its 'savage' and 'barbarian' past. Scholars have done an enormous amount to excavate this discourse, but their narratives invariably draw to a close with the fading of the naked language of civilizational superiority after the First World War. I argue that this is a mistake, confusing the transformation of the concept of civilization for its disappearance. Successive crises within Europe - fratricidal barbarism, imperial disintegration, fascism and Bolshevism - and the simultaneous rise of anti-colonial resistance and non-European powers, led during the interwar years to what Paul Valery diagnosed as Europe's 'deminutio capitis'. Europe's status as a singular civilization at the head of a linear process of asymptomatic progress was shattered, replaced with the aporetic possibility of decline, and the looming threat of global pluralisation. What followed over the subsequent century, I contend, were a long series of attempts to reinvent the concept of civilization to reimagine a post-European world order in the shadow of this 'deminutio capitis'. I analyse this discourse on two planes. First, I examine what I call the 'problem-space' of Europe's deminutio capitis. Western theorists of world order have repeatedly confronted the problem of civilization as that of, first, interpreting the nature and trajectory of the crisis of Europe's deminutio capitis, and second, reformulating the concept of civilization to both take into account that crisis, and to restore Europe - or 'the West' - to its status as the seat of world history. I call this a problem-space because the relative diminution of Europe on the world stage is only a peculiarly theoretical problem relative to the assumptions about historical time built into the traditional concept of civilization. It is only when fixed on this terrain, the terrain of Europe's imperial modernity, that Europe appears in need of rehabilitation, and that rehabilitation must take the form of a vindication of its modernity. Theorists have, I contend, been trapped within this matrix of assumptions. Second, I trace the genealogical mutations of the concept of civilization as it has been successively reappropriated to imagine and legitimate new world-ordering projects, from a German imperial mundi and a revivified British Empire (interwar), to the North Atlantic alliance and a dominative American empire (high Cold War), to the expansionist liberal interventionism that succeeded it (1990s). I chart three transformations in the concept of civilization, corresponding to each of these periods: its 'pluralisation', 'liberalisation', and 'deterritorialization'. I combine these two planes of analysis in a single narrative through a version of what David Armitage calls 'serial contextualism'. I string together synchronic portraits of theorists who have grappled with and responded to Europe's deminutio capitis, while stringing these portraits together into a diachronic picture of the genealogical metamorphoses of the concept of civilization. Oswald Spengler, Arnold Toynbee, Karl Popper, James Burnham, Frances Fukuyama and John Rawls are all given starring roles in this narrative, though in each case, cast within the context of a wider ensemble.