1, nationalism has promoted the emergence of the nation-state. In medieval Europe, there were basically no concepts of nation and country. At that time, although there were various races in Europe, such as Germans, Celts, Slavs, Greeks, etc. This is just a broad geographical concept, just as they think people in the New World are Indians. They simply divided Europeans according to their geographical location through different names, but they did not form a sense of national belonging and honor. At that time, the so-called countries in Europe mainly emphasized territory. The duke has his own territory somewhere, so he is the ruler of that territory. He can divide his territory into several areas, and divide them as his own territory among Marquis and Ors, and Marquis and Ors will be responsible for him. In the territory, the Lord is the "king" and others have no right to ask about the affairs of his territory. Europe in Middle-earth is made up of such large or small territories. Until modern times, the development of commodity economy led to the rise of the civil class, which had no territory and was not a feudal Lord, but they needed to express their political demands. As a result, the civil classes with common interests in a certain area United to interfere with feudal lords and demanded political rights. In this way, the national consciousness in the modern sense led by the bourgeoisie began to awaken. At that time, this national consciousness was mainly manifested by the bourgeoisie with common interests in the same region and the bourgeoisie with conflicts of interests in the region. The bourgeoisie in the same region has formed a common sense of belonging, that is, a sense of national belonging. This modern nation is a nation with common interests, not a nation in a purely geographical sense. The bourgeoisie has no territory. In order to gain political rights, they had to confront feudal lords through representative system. Later, this representative system defeated the feudal Lord system, and a modern country based on social contract theory came into being. This modern country is a nation-state established by the bourgeoisie belonging to the same nation with a sense of national belonging.

2. Nationalism has promoted the development of capitalism. During the transition from Europe to modern times, feudal lords and the Catholic Church were two major obstacles. Nationalism promoted the birth of the nation-state, undoubtedly removed the obstacles of feudal lords in the early Qing Dynasty and laid the institutional foundation for the development of capitalism. At the same time, the love for our nation also inspires people to struggle to get rid of the Roman Catholic Church and establish their own Christianity. With the development of religious reform, this struggle gradually swept through western Europe. The development of religious reform undoubtedly lifted the ideological imprisonment of capitalist development, and also clarified the economic and political oppression of the Roman church. At the same time, nationalism makes the struggle between the bourgeoisie rise to the struggle between all ethnic groups, which inspires the sense of crisis and fighting spirit of all ethnic groups. All of the above have promoted the development of capitalism and the modernization of the world to a corresponding extent.

3. Nationalism has promoted the struggle of the oppressed nationalities for national liberation. Nationalism has promoted the formation of European and American nation-states and the development of capitalism, but at the same time, the unjust colonial expansion of European and American capitalist countries in the world has oppressed almost all ethnic groups in other parts of the world. American Indians and later immigrants, African blacks, China, Indians, etc. There is no doubt that these ethnic groups have suffered greatly from the collision of civilizations. The spread of European nationalism has undoubtedly had a great impact on the struggle for national independence of these ethnic groups. The national independence of the United States and the establishment of a nation-state, mainly the Latin American war of independence led by American independence and Bolí var, the great national uprising led by Indian Queen Zhang Xi, and the anti-imperialist movement of the Boxer Rebellion in China, are all struggles of the oppressed nations for national independence. Although some failed, they undoubtedly had a far-reaching impact on their nationalism.

4. The beneficial influence of nationalism on culture at the spiritual and cultural level. Nationalism emphasizes the sense of identity and belonging to the nation, which is conducive to stimulating national self-esteem and self-confidence, promoting national unity and enhancing national cohesion. It can form an upward, enterprising and self-reliant emotion within a nation, fully stimulate people's potential, and thus promote the development of this nation. At the same time, the recognition and sense of belonging to the nation will make people consciously protect their traditional culture, which is conducive to the inheritance of national culture and the development of cultural diversity in the world.

Disadvantages of nationalism:

1, nationalism can easily lead to ethnic division. Although nationalism promotes the development of nation-state, excessive nationalism can easily lead to ethnic separatism, and the direct consequence of ethnic separatism is ethnic division. The vast majority of countries in the world are multi-ethnic countries. There are many nationalities in a country, and each nationality has its own interests. When these interests are not satisfied, it is easy for these ethnic groups to use nationalism as an excuse to set off a national separation movement to split the country and form their own political power. Even in some countries, the government gives some ethnic groups many special rights that are superior to others, but the fanatical nationalists of these ethnic groups are still not satisfied. They engage in activities to split the country regardless of the consequences, and even collude with foreign countries at the expense of the interests of their own people.

Nationalism can easily lead to terrorism. It is good to love our nation, but when our nation is in a weak position and oppressed by a powerful nation, a strong nationalist complex may turn into terrorism. The first recognized terrorist incident in the world was the Sarajevo incident in 19 14. Despite Serbia's opposition, Austria-Hungary occupied Serbia in Bosnia and Herzegovina, and held a military exercise against Serbia in Bosnia and Herzegovina on Serbia's shame day (the day when Serbia was conquered by Turkey centuries ago), which completely angered the Serbs. However, Serbia was unable to confront Austria-Hungary at that time, and the strong national complex of the Serbs had nowhere to vent, which directly led to the Sarajevo incident and brought devastating disasters to the world. In addition to this pure terrorism, national separatism often uses terrorism to achieve the purpose of splitting the country. Nowadays, terrorism has become the number one threat to world peace.

Nationalism can easily lead to racial conflicts. Different nationalities have their own interests, so conflicts will inevitably arise between them. This is a normal phenomenon. However, in some countries and regions, this nationalism to safeguard national interests has evolved into racism, that is, it emphasizes that one's own nation is superior and other nations are inferior. The most typical examples are the discrimination of American whites against blacks and the slaughter of Indians. In addition to racism, simple racial conflicts are constantly staged all over the world, and the discord between France and Germany is a typical example.

Nationalism can easily lead to national tyranny. Nationalism emphasizes the absolute sovereignty of the nation-state and excludes individual autonomy, so it is very likely to suppress and deprive individuals of their rights and freedoms and form an unconstrained absolute autocratic political sovereignty at home and abroad. In the view of nationalism, the most important living unit of human beings is the nation and race, and all other living units, especially individuals, are insignificant. Even the personal sacrifice of national members at no cost can bring about the realization of national interests. In some countries, under the pretext of safeguarding the interests of the whole nation, governments or individuals have forcibly pursued autocracy at home and wantonly violated the rights and freedoms of their own people. This tyranny in the name of nationalism is typical of Japanese militarism. Japanese militarism began to appear after the Meiji Restoration, suppressing the working people at home and expanding wildly abroad. History has proved that militarism can only bring devastating disasters to the country in the end.

To sum up, nationalism has made great contributions to the modernization of the world, but in contemporary times, it has become the root of modern violence, and the problems it has caused have seriously threatened world peace and the common interests of people all over the world. How to solve the problems brought by nationalism has become a major topic in the world.