In the 17th century, a vision arose which was to captivate the Western imagination for the next 300 years: the vision of Cosmopolis, a society as rationally ordered as the Newtonian view of nature. While fueling extraordinary advances in all fields of human endeavour, this vision perpetuated a hidden yet persistent agenda: the delusion that human nature and society could be fitted into precise and manageable rational categories. Stephen Toulmin confronts that agenda - its illusions and its consequences for our present and future world.