This volume collects papers from Hugo Sonnenschein's students with the aim of demonstrating his tremendous impact as an advisor. The papers span decades, with the earliest coming from his advisees in the first years of his career and the most recent coming in the last two years after his return to research and advising that followed his adventures as a university administrator. Each paper is accompanied with a preface by the student that provides background on the paper and indicates Hugo's influence on its genesis. The papers all lie in microeconomic theory, and moreover all make fundamental contributions to the foundations of the theory.