Wallerstein starts with an intellectual autobiography, describing how fieldwork in colonial and newly independent Africa convinced him that tribes, communities and nation states are fragments of something larger. His proposed unit is the world-system, a zone held together by an extensive division of labour and containing many cultures, and he argues that one such zone, a capitalist world-economy, formed in Europe across the long sixteenth century and has lasted five hundred years without consolidating into an empire. That refusal to become an empire is the source of its strength, since capital operates in an arena wider than any single state can control, and political entities absorb losses while gains stay in private hands. Regions are sorted into core, periphery and a semiperiphery that he insists is structurally necessary rather than a residual category, with the most skilled and capitalised tasks reserved for the top. Market forces widen these gaps as the system develops.