Since ancient times, democratic politics has opposed the poor to the rich. This is the central theme of Aristotle's Politics, that of the Florentine History of Machiavelli where the popolo minuto faces the popolo grasso, that of Marx with the proletarians drawn up against the bourgeois. But for the past twenty years, the poor are no longer opposed to the rich but to the poorest of them, the migrants, although xenophobia is no worse than in the past and the differences in wealth are increasing. The seminar will question this strange change in which migration has become a major political issue in France and will look at similar cases abroad and at other times. Intervene heads of institutions dealing with migration, sociologists and political philosophers French and foreign.