This book presents a new constitutional argument for the legitimacy of evolutive interpretation of the ECHR. It constructs a model, in which evolutive and static constitutional principles are balanced with each other. The author argues that there are three possible interpretive approaches in time-sensitive interpretations of the ECHR, but that only one of them is justifiable by reference to the constitutional principles of the ECHR in every single case. The ECHR's constitutional principles either require an evolutive or static interpretation or they do not establish a preference relation at all, which leads to a margin of appreciation of the member states in the interpretation of the Convention. The balancing model requires the determination of the weights of the competing evolutive and static constitutional principles. For this purpose, the author defines weighting factors for determining the importance of evolutive or static interpretation in a concrete case.