Debt is understood as occurring ‘in between,’ i.e. between past and future, trade and theft, and between two partners who put themselves in a position of voluntary inequality. Without ignoring financial debt, this study focusses on other types: moral debts owed between two individuals, social debts owed by different types of actors within a community, political debts owed between citizen and state, and between states. Definitions of justice in Plato’s Republic 1, and Aristotle’s EN5 demonstrate how corrective justice (arithmetical) mirrors Cephalus’ views of debt – repaid mechanically, without consideration of conditions, amounts, parties involved; whereas distributive justice (geometrical) recalls Polemarchus’ – the owing of what is ‘fitting’ to the parties involved (their nature, needs, etc.). Answers are proposed on whether creditor or debtor are culpable for the debt, how errant debtors should be handled (punished), and what kinds of debts are legitimate. Aristotle’s analysis is then transferred almost directly into the language of social debts. The examples of Thrasymachus and Solon demonstrate how a miscalculation of the repayment of these debts precipitates the dissolution of both the relationship and the polis-wide network of social relations. This abstract analysis of justice implicitly underlies Aristotle's subsequent analyses of relationships (1)of friendship and (2)within the household/oikos (husband-wife, master-slave, parent-child). Debt is also observed in the political and inter-political spheres, with dysfunctional debt relationships being the main precipitating factor in Plato’s account of morally declining political constitutions and characters. Thucydides, too, explores stasis and political decline through an economic lense, while his Pericles utilises debt relations in the establishment of political unity, and in depicting the ideal of political success, with the citizen as creditor to the city, and the city as creditor in inter-political policy. This feeds into an analysis of the merits of enacting inter-political policy via the debt-relationship of charis, versus coercion.