Viewed retrospectively, the most influential thinkers of the nineteenth century were Karl Marx (1818–83) and Charles Darwin (1809–82). Two of their central concepts, class struggle and evolution, both focused on the idea of ‘struggle’, and clearly had some common origin, as Marx at least recognised. Together they provided a definitive leitmotif for fin de siècle Europe and America, whose inheritance was bequeathed to the twentieth century, at least to 1945 (for Social Darwinism), and to 1991 (for Marxism).