Ostracism was adopted as a safety valve in the democratic process since, according to Aristotle, the aim (of this new institution) was to give the people the power to neutralize those who were dominating or exerting undue influence by virtue of their wealth or some other political strength. Aristotle, Politics, 1284a, 20.
Ah Ha!, that's a good idea. Probably more socially acceptable than the old French Solution (much later).
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From @biodiversitybush