Federici's best known work, Caliban and the Witch: Women, the Body and Primitive Accumulation, expands on the work of Leopoldina Fortunati investigating the reasons for the witch hunts[6][7][8][9] of the early modern period, but giving a feminist interpretation. In it, she argues against Karl Marx's claim that primitive accumulation is a necessary precursor for capitalism. Instead, she posits that primitive accumulation is a fundamental characteristic of capitalism itself—that capitalism, in order to perpetuate itself, requires a constant infusion of expropriated capital.