Nationalism as an ideology is modern. Throughout history, people have had an attachment to their kin group and traditions, to territorial authorities and to their homeland, but nationalism did not become a widely-recognized concept until the 18th century. There are three paradigms for understanding the origins and basis of nationalism. Primordialism (perennialism) proposes that there have always been nations and that nationalism is a natural phenomenon. Ethnosymbolism explains nationalism as a dynamic, evolutionary phenomenon and stresses the importance of symbols, myths and traditions in the development of nations and nationalism. Modernism proposes that nationalism is a recent social phenomenon that needs the socio-economic structures of modern society to exist.
There are various definitions of a "nation", however, which leads to different strands of nationalism. Ethnic nationalism defines the nation in terms of shared ethnicity, heritage and culture, while civic nationalism defines the nation in terms of shared citizenship, values and institutions, and is linked to constitutional patriotism. The adoption of national identity in terms of historical development has often been a response by influential groups unsatisfied with traditional identities due to mismatch between their defined social order and the experience of that social order by its members, resulting in an anomie that nationalists seek to resolve. This anomie results in a society reinterpreting identity, retaining elements deemed acceptable and removing elements deemed unacceptable, to create a unified community. This development may be the result of internal structural issues or the result of resentment by an existing group or groups towards other communities, especially foreign powers that are (or are deemed to be) controlling them.National symbols and flags, national anthems, national languages, national myths and other symbols of national identity are highly important in nationalism.
Title page from the second edition (Amsterdam 1631) of De jure belli ac pacis
The terminological use of 'nations', 'sovereignty' and associated concepts was significantly refined with the writing by Hugo Grotius of De Jure Belli ac Pacis in the early 17th century. Living in the times of the Eighty Years' War between Spain and the Netherlands and the Thirty Years' War between Catholic and Protestant European nations (Catholic France being in the otherwise Protestant camp), it is not surprising that Grotius was deeply concerned with matters of conflicts between nations in the context of oppositions stemming from religious differences. The word nation was also usefully applied before 1800 in Europe to refer to the inhabitants of a country as well as to collective identities that could include shared history, law, language, political rights, religion and traditions, in a sense more akin to the modern conception.
Nationalism as derived from the noun designating 'nations' is a newer word; in English the term dates from 1844, although the concept is older. It became important in the 19th century. The term increasingly became negative in its connotations after 1914. Glenda Sluga notes that "The twentieth century, a time of profound disillusionment with nationalism, was also the great age of globalism."