The twenty-two papers collected in this volume illustrate the itinerary of Henry Tulkens, an applied theorist, on the occasion of his retirement from teaching. The collection is structured in four parts: decentralized resource allocation processes for public and private goods; environment, public goods and externalities; efficiency analysis; and fiscal competition and optimality. The four pictures above evoke a key concept, method or model used in each of these four parts: MDP-type processes to determine feasible paths to efficiency and coalitional stability; climneg world simulation model to explore alternative environmental scenarios for the planet; free disposal hull efficiency analysis to drop convexity and help deal with outliers; and non cooperative fiscal equilbria to characterize the outcomes of fiscal competition.