Federalism is a very familiar form of government. It characterises the first modern constitution-that of the United States-and has been deployed by constitution-makers to manage large and internally diverse polities at various key stages in the history of the modern state. Despite its pervasiveness in practice, this book argues that federalism has been strangely neglected by constitutional theory. It has tended either to be subsumed within one default account of modern constitutionalism, or it has been treated as an exotic outlier - a sui generis model of the state, rather than a form of...