Since the late 1950s the concept of human capital, understood as the stock of knowledge, skills, and abilities that determine individual productivity, has become one of the central tools with which economists explain both individual success and economic growth. During the latter half of the 20th century complementing concepts such as social capital, meaning the value of social networks and norms of reciprocity, and intangible capital, meaning the investments in knowledge and innovation generation, have emerged. The term intellectual capital is sometimes used as a major concept to bind different forms of intangible capital. This study focuses on the conceptual equivalents of these ideas in 19th century English, French, and German economic thought in order to show that most of the phenomena now connected to human capital, intangible capital, intellectual capital, and social capital were already extensively discussed as capital in different phases of the long 19th century (1789-1914). Equally, many of the arguments presented since the late 1950s against the extension of the concept of capital to human beings, human attributes, knowledge, reputation, social norms, or social relations after the new emergence of these ideas were also part of the earlier discussion. A better understanding of past debates about the definitional scope and functional role of capital in economic theory should help to avoid unintentionally circular or repetitive argumentation which presents what were in fact once solid arguments of political economy as previously unattainable insights made in the past five decades.