A New Statesman Book of the Year A critical analysis of the transformation of constitutionalism from an increasingly irrelevant theory of limited government into the most influential philosophy of governance in the world today. Constitutionalism is universally commended because it has never been precisely defined. Martin Loughlin argues that it is not some vague amalgam of liberal aspirations but a specific and deeply contentious governing philosophy. An Enlightenment idea that in the nineteenth century became America’s unique contribution to the philosophy of government, constitutionalism was by the mid-twentieth century widely regarded as an anachronism. Advocating separated powers and limited government, it was singularly unsuited to the political challenges of the times. But constitutionalism has since undergone a remarkable transformation, giving the Constitution an unprecedented role in society. Once treated as a practical instrument to regulate government, the Constitution has