Ostracism (Gr., a fragment of tile, a shell), in Athenian history, the banishing from the state for a limited period of a person deemed dangerous to the republic. Grote defends ostracism as a wise measure devised by Clisthenes for removing quietly from the state a powerful party leader, before he could carry out any plot against the government. At first the banishment was for ten years, but it was afterward reduced to five. It involved no dishonor, nor any loss of property. The senate and public assembly determined whether ostracism was advisable; a day was then appointed, and a space in the agora enclosed, having ten entrances for the ten tribes, through which the citizens passed, each depositing in a prepared receptaele an oyster shell or potsherd inscribed with the name of the person whom he wished banished. The archons counted the votes, and if there were 0,000 votes against any one person, that person had to withdraw from the city within ten days. Among distinguished men ostracized were Aristides, Themistocles, and Cimon.