This chapter completes the defense of constructivism. It explains why a problem-based approach to constructivism is not subject to the final criticism associated with the Euthyphro dilemma. The chapter argues that although the normative force of basic principles supports the normative purchase of substantive political principles, and although the normative purchase of substantive political principles grounds the normative authority of political institutions, it does not follow that basic principles ground the normative authority of political institutions. A constructed set of substantive political principles must serve as fundamental political principles for determining the normative authority of political institutions and their assigned powers.