Human beings are social beings. They form societies and manage to combine their individual skills for the advantage of the whole group. However, given a specific society, individuals have an incentive to free-ride on the effort provided by others and not contribute to the collective interests. Even more so, without restrictions, each individual has an interest to take from others what is not his. Social Organization offers a collection of four papers dealing with different aspects of how societies may deal with the problem of free-riding. The papers constitute four parts. Broadly speaking, the first part is interpreted as showing the need for social institutions. In line with the scholars of classical economics, the remaining three parts offer an investigation of the design of three distinct forms of institutions, namely morality, social norms, and the law. The latter three papers take Adam Smith's moral and legal philosophy as starting point.