By assessing the impact of norms on decision making, this book argues that norms influence choices by providing reasons rather than by being causes for action. It approaches the problem via an investigation of the reasoning process in which norms play a decisive role. Professor Kratochwil argues that depending on the strictness of the guidance that norms provide in arriving at a decision, different styles of reasoning with norms can be distinguished. To that extent, Kratochwil argues that "law" is characterized by a particular mode of reasoning that is a subset of "practical reasoning." While the focus in this book is largely analytical, the argument is developed through the interpretation of the classic thinkers in international law such as Grotius, Vattel, Pufendorf, Rousseau, Hume, and Habermas.