This is a book about what people imagine it means to live in a world where private property is dominant, and their fears - and sometimes hopes - about living in a future world where private property has disappeared. In the propertied imagination, private property is a fragile thing, an institution beset by terrifying enemies and racialised and gendered mobs: Levellers and Diggers, socialists and anarchists, fervent religious radicals, abolitionists, feminists, and haughty welfare-state bureaucrats. The history of private property is the history of a recurring nightmare that one or another of these groups would storm the castle and take control. That threatened social chaos is the central unifying story of this book. Private property and the fear of social chaos starts by charting the thinkers who laid the foundations for how we understand private property, including Locke, Burke, Marx and Engels. The book looks at how their ideas have been put into practice in ways that continue to shape the modern world, from Harry Truman's housing policies and the anti-abolitionist George Fitzhugh to Margaret Thatcher and Elon Musk. Arguing that the spectre of 'the mob' has been intimately interconnected with the idea of private property throughout capitalist modernity, the book ambitiously narrates this history from the early colonisation of the Americas to Silicon Valley, and the future of human colonisation in space.