This book, calling on the Weberian idea of rational law and by drawing on the renowned Protestant Ethic and the Spirit of Capitalism, seeks to demonstrate that formal legal rationality, proper to European continental law of the late nineteenth century and early twentieth century, has a distinct “protestant ethic” component, more precisely of Calvinistic values—which, as we know, were also present at the English Revolution of 1688 (the Glorious Revolution) and, soon after, were at the basis for the creation of the Constitution of the United States. The religious values that determined the protestant way of life, which led to the development of capitalism, demanded a rational and predictable law, expressed by the scope and clarity that were peculiar to scientific positivism or the German conceptualism of the beginning of the twentieth century.