The institution of group ownership has rarely been studied in political philosophy. Instead, most property theories in this discipline focus on arguments for and against individual ownership. When group ownership is discussed at all, moreover, this is often in the specific context of workplace governance. What is lacking is a general normative justification of group ownership that explains when and why it is valuable that individuals share a resource. This dissertation provides such a justification. The particular conception of group ownership that it defends is the institutional realisation of a sharing practice, called sharing in common. In this practice, members of a private group determine collectively and democratically how their share...