In the fourth volume of the Vienna Lectures on Legal Philosophy, scholars in contemporary jurisprudence and constitutional theory discuss who gets to decide and who gets to act when constitutional law is silent or fundamentally controversial. It is the very purpose of Constitutions to settle disagreements: to determine who gets to decide and who gets to act when it comes to the polity and its members. But what if, instead of settling disagreements among those subjected to it, the Constitution itself, its end, its functions, its meaning, its existence, becomes the subject of disagreements? What if the Constitution raises issues it is unable to address from the very outset? Who gets to decide then and who gets to act?In a time in which constitutional crises seem to be too ubiquitous to still count as exceptions, questions such as these are asked with ever-increasing urgency. The answers to these questions cannot be found in arguments based on contingent legal stipulations but have to reach beyond the vague and fleeting instructions of positive law.