1contemporary classical studies using archaeological research of the thousands of ostraka excavated in the Agora and Kerameikos. In the first part of this article, I describe the institution of ostracism and distinguish three procedural qualities-temporal, participatory, and inclusive requirements. These are crucial as they illustrate the self-limiting nature of the Athenian model of democratic self-defense. In the second part, I discuss the purpose of ostracism.Was it aimed at preventing the emergence of tyranny? Or are we justified in calling it an anti-aristocratic tool? I conclude this section by arguing that the goal of ostracism was positive; to protect and promote democratic stability, and negative only inasmuch as it excluded any person who acted against this end. In the conclusion, I draw on my findings to build a framework of democratic self-defense that challenges some of the most popular contemporary paradigms.Handing over to the demos the power to exile a prominent political figure was as generous as it was risky. It could result in stripping the city of its best leaders and leaving it at the mercy of mediocre demagogues: this has been indeed a widely held criticism against ostracism. The famous anecdote that had Aristides the Just being ostracized because the demos envied his virtues (Plutarch, Life of Aristides, 7.4. trans. 2008) betrays the pragmatic fear of subjecting Athenian day-to-day politics to the caprice of the demos. This controversial aspect of ostracism has led critics of ancient direct democracy from Plutarch to John Adams in the 18 th century and even today to use ostracism as an illustration of the irresponsible and illiberal aspect of Athenian democracy (Forsdyke, 2005, p. 144; Lane, 2014, pp. 115-127;Roberts, 1994). Yet in reality the procedure was designed in a careful and sophisticated manner so as to prevent its overuse or abuse.The Athenian historian Philochoros writing in the 3 rd century BCE offers a concise description of the practice:Ostracism takes place as follows. Before the eighth prytany, the people vote on whether it is necessary to hold an ostracism. If it is necessary, the agora is fenced in with boards, leaving ten entrances, through which the people enter in their tribes, and deposit their sherds [ostraca] with the writing facing downwards. The nine archons and the council oversee the process. When the sherds have been counted to determine who has the most votes (which must be not less than 6,000), then this person must, after settling his personal commitments, leave the city within ten days, for a period of ten years (this was later reduced to five years). He is allowed to receive income from his possessions, but he must not come nearer [to Athens] than Geraestum, the headland on [the coast of] Euboea. (Philochoros of Athens, Fragment 79b, trans. 2016) 1The procedure of ostracism thus involved several stages, rituals, and requirements. Some of its features were purposefully self-limiting. They included: (a) temporal restrictions, including an annual call for os...