Do constitutional changes take place only through legislative amendment of the Consti-tution or judicial overruling? Or Constitutions change even in contact with facts? Is there a normative power of the factual, or the legal system is exclusively made by formal acts? The paper tries to provide an answer to these questions, and proposes the concept of ‘constitutional mutation’ (Verfassungswandel) elaborated by German scholars by the end of XIX Century as a tool to focus on otherwise invisible alterations of the constitu-tional document.
Keywords: Constitution, interpretation, constitutional amendment, constitutional mutation