This chapter introduces a set of tools from the social sciences, including social capital theory, the theory of networks, and the sociology of hierarchies. It explains how the mechanisms designed to evaluate reputations function and what makes them reliable. It also focuses on the assessment and reliability of reputations. People emit signals meant to convince others of the genuineness of their reputations. Similarly, all things, objects, ideas, and indeed everything that points beyond appearances to hidden qualities, emit signals that inform people more or less credibly that certain qualities really exist. The chapter also explains that reputation is the result not only of strategic positioning but also of the way in which such positioning is perceived by others.