A nation is imagined because its members will never know most of their fellow members yet hold in their minds an image of communion with them. It is imagined as limited (bounded by finite borders beyond which lie other nations) and as sovereign, and as a community conceived as deep horizontal comradeship regardless of actual inequality.
The market-driven mass production of books and newspapers in vernacular languages created unified fields of exchange below Latin and above spoken dialects, letting readers who would never meet become aware of hundreds of thousands sharing their particular language. This fixed languages, gave them a new stability, and made it possible to imagine the nation.
Modern nationalism depends on conceiving time as homogeneous and empty, measured by clock and calendar, in which unrelated people perform parallel actions simultaneously. The novel and the newspaper are technical forms that embody this: readers absorb an image of many anonymous others acting at the same moment, producing the sense of a community moving steadily through history.
The earliest nationalisms arose not in Europe but among creole functionaries in the Spanish American and North American colonies, whose careers were capped at the colonial boundary and could not ascend to the metropole. These bounded administrative pilgrimages, combined with provincial newspapers, defined the territorial unit people came to imagine as their nation.
Late colonial states produced nationhood through three institutions: the census classifying people into bounded identity categories, the map rendering territory as a logo-like bounded shape, and the museum presenting a lineage of monuments as the nation's heritage. Together they taught populations to picture the state as a demarcated, countable, historically rooted entity.
When popular linguistic nationalisms threatened multi-ethnic empires, ruling dynasties adopted nationalism from above, stretching the tight skin of the nation over the gigantic body of the empire through compulsory state schooling, standardized language, and controlled migration. This conservative, state-led nationalism was a deliberate anticipatory strategy to retain power, not a grassroots awakening.