This chapter for the forthcoming book, The Law and Economics of Possession (Yun-chien Chang, ed), explores the law of possession as an application of a heuristic (a simple decision making strategy devised to solve complex problems, part of System 1 thinking in Daniel Kahneman’s famous formulation). Since the law of property is essentially the law of belongings, its first task is to determine to whom things belong. There are all sorts of complicated inquiries that could be undertaken to figure out and justify an incredible range of answers to this question. Alternatively, there is a simple inquiry that provides a simple answer: A thing belongs to its possessor. This is the possession heuristic. The chapter canvases possession doctrines and ultimately argues that some current controversies in property, about the centrality of exclusion versus a social obligation norm in property, can be at least partly reconciled by viewing possession as a heuristic.