Along with the renewed interest in the Austrian school of economics over the last two decades, important advances have been made in applying its princples to concrete issues that typically face market economics. However, very little has been done in the area of externalities and the concept of social efficiency. The overarching purpose of this book is to establish a sound theoretical basis for further empirical and public policy analysis in the area of externalities. In order to do this, a general theory of welfare economics is required. The author offers an alternative to the conventional neoclassical welfare paradigm -- his construct does not include perfect competition or general equilibrium. After the author develops his theory of welfare economics, he interprets externalities in light of the theory and discusses policy remedies and directions for further research.