Why do people bond with each other and with systems of authority? To understand the social contract's specific meaning and current relevance, it is necessary to return to its origins and bring out elements often passed over in more general discussions. A thematic analysis process is used to identify the social contract’s key themes from the social contract theories by Hobbes, Locke, Rousseau, and Rawls to conceptualize a social contract’s key elements and sources of legitimacy. This analysis identifies the social contract’s dual nature consisting of two equally relevant pacts—a societal pact and a governance pact. Drawing on the thematic analysis of this social contract theory literature, the sources of legitimacy that correspond with the social contract’s key elements are identified, noting that these are unique to specific geopolitical, historical, and cultural contexts. Perceptions of legitimacy form the intangible glue that bonds people together as a society and with a political authority to form a social contract, leading to consent, political obligations, and societal and political trust. Differences between political social contracts and political orders, and between political and non-political social contracts are explored.