This article seeks to contribute to the history of the idea of 'middle class', an idea that was fundamental to Aristotle's philosophy but disappeared from the repertoire of political thinking for centuries, re-emerging shortly before the French Revolution to be developed by Diderot and other French liberals. The modern notion of 'middle class' is compared with that of Aristotle, and the similarities between the two contexts of emergence -- the crisis of Ancient Greek democracy and that of the French Ancien (...) Régime -- are explored to cast new light on the meaning and political function of that idea, and on the metaphorical operations it performs. (shrink)