Immanuel Kant's Perpetual Peace is widely recognized as a foundational International Relations text. My research has uncovered a variety of competing interpretations of the work since its initial publication in the late eighteenth century. This thesis examines English-language commentary on the treatise from the mid-nineteenth to the end of the twentieth century. It demonstrates the existence of two distinct patterns of interpretation. According to my analysis, interpretations from the mid-nineteenth to the mid-twentieth century assert that the text endorses peace proposals above the state level. This collection of interpretations constitutes Pattern One. Interpretations from the mid-twentieth century to its end, however, maintain that the text is in favor of peace proposals at the state level. This collection of interpretations constitutes Pattern Two. It is argued that the principal explanation for the existence of these patterns resides in the rise and decline of hopes for peace through international organization. A subsidiary explanation is that the patterns reflect the steady increase in the number of liberal states in the western hemisphere over the past century and one-half. These patterns and their explanations provide a comprehensive historical background and analytical framework for understanding Perpetual Peace which enables academics and students of International Relations to better understand and appreciate its complex meaning and to think beyond the conventionally accepted interpretations of the day.