Three families of social capital concepts are discussed: (fa1) trust, (fa2) ease of cooperation, and (fa3) network. In the language of game theory, social capital is the excess propensity to play cooperative solutions in prisoners’ dilemma games. The three families lead to different definitions, and thus to different measurement methods. Some measures are theory‐near, while others are easy‐to‐use proxies. It is shown that all definitions and measures are related. The ‘social capital dream’ is that all definitions try to catch aspects of the same phenomenon, so that all measures tap the same latent variable. It is discussed whether this dream is likely to come true.