In this context, nationalism is the feeling of identification with one’s country. Before modern times in Europe, people typically did not identify with a country. A person in what is now France would not have thought of themselves as French. Instead, they would have identified with their locality or, at most, their region. They would have seen themselves, for example, as Bretons more than as French people. With the coming of nationalism, they would have come to identify themselves as French.
Nationalism arose from two main sources. These sources were romanticism and liberalism. Romantic nationalism emphasized a sort of spiritual connection between the country and the individual. It emphasized the importance of whatever it was that people of the country felt that they had in common. For example, it could emphasize the importance of language or of ethnicity. Alternatively, it could arise, as with Revolutionary France, from dedication to a given set of ideals.
Liberal nationalism emphasized the consent of the governed. Liberal ideas, like those of John Locke, held that government was only legitimate if the people gave their consent to be governed. In nations where liberal political systems took hold, people were nationalistic because they felt that they had agreed to be part of a national political system. Both liberal and romantic nationalism came about largely because of the rising numbers and power of the middle class.
The two kinds of nationalism are at least somewhat compatible. Romantic ideals can cause people to be more likely to consent to be governed by a government that shares their ethnicity or their views. However, the two can also be incompatible. This is particularly the case when nationalism causes people to hate outsiders. The extreme example of this is Nazi Germany. There, extreme nationalism caused people to have no tolerance for dissenters or for outsiders like Jews. When nationalism is taken to extremes, it destroys liberal democracy. It does this because it does not respect the political and human rights of outsiders, rights which are fundamental to liberal democracy.