Important social capital definitions focus on relationships, how people are connected. Relationships depend on commonalities, what people share. Commonalities may be earned or inherited and include shared emotions. Empathy is an important shared emotion because it enables us to internalize each other's well-being, the motivation for important economic outcomes. This article supports the definition of social capital as the empathy one person or group has another person or group, the object(s) of their social capital. Because Adam Smith emphasized the importance of sympathy (what we now call empathy), we recognize him as contributing to the social capital definition supported here. Members of social capital-rich networks, compared to nonmembers, are more likely to produce and exchange relational goods (intangible signals that satisfy our socio-emotional needs). They are also more likely to exchange commodities (things that satisfy our physical needs) on preferential terms, more likely to cooperate, more likely to invest in public goods, more likely to support institutions, more likely to enjoy equal commodities incomes, more likely to limit negative externalities, and more likely to be happy. Social capital, however, has a dark side. It is that the benefits enjoyed by members of social capital-rich networks are often denied or not