Abstract
Legal and sociological theories of sovereignty disagree about the role of legal and social matters in grounding state power. This paper defends a constructivist view, according to which the constitution is a judgment of practical reason. The paper argues that a constitution sets out a comprehensive institutional architecture of social life in terms of principles and official roles that are necessary for any legitimate scheme of social cooperation to exist. It follows that legal and sociological theories of sovereignty capture only part of the truth of sovereignty. Legal reasoning engages with political power, but it is not determined by it. There is no causal chain between power and validity, as suggested by the legal positivists. The relation between power and law is interpretive, not causal. It follows that the circularity of law and the constitution, namely the fact that the law makes the constitution and the constitution makes the law, is not a vicious circle. It is part of an ordinary process of deliberation.