For many, the prohibition of instrumentalization, which states that one must never treat other people merely as means, represents a fundamental moral truth. This book is an attempt to grasp and justify this view more closely. The prohibition of instrumentalization plays an important role not only in our everyday morality but also in moral theoretical discussions. Various practices are criticized as impermissible on the grounds that they instrumentalize people. But what does it mean to treat others merely as means? This book argues that there is a connection between impermissible instrumentalization and the violation of a person's dignity. The relationship is elaborated in the explication of the concept of dignity. In certain cases, the impermissible instrumentalization of individuals violates their dignity.