Internationalism
Generally, internationalism is the belief that the peoples of the world should unite and connect across national boundaries, looking beyond what is best for individual nations to see what is best for the world.
Liberal nationalism is based on applying the core principles of liberal individualism to the nation. Nations have the right to self-determination as much as individuals have the right to individual autonomy and freedom. The liberal nationalist aim, therefore, is a world of independent nation-states. Liberal nationalists also assume that independent nation-states will seek to co-operate with each other as and when they need to - economically, educationally and culturally. This will create interdependence as they trade goods and services, share ideas and exchange cultures.
The key aim of this co-operation and interdependency is to secure an internationally stable and without resorting to violence. This led liberals to put their faith in supranational institutions - that exist above national institutions such as the EU or the UN, to help resolve conflicts between nations. Just as sovereign individuals need to be kept in check by a state, so sovereign nation -states need to be kept in check by supranational institutions.
Socialist internationalism
The other well known and more typical form of internationalism is Socialist Internationalism which is largely incompatible with nationalism. Socialist Internationalism is concerned with extending the idea of co-operation, community and humanity across the world believing that humans are not naturally divided into nations and are instead connected to the whole of humanity 'whatever country they happen to be living in. International socialism, is the perception of all communist revolutions as being part of a single global class struggle rather than separate localized events
It was Karl Marx who said, 'The working man has no country'. Marx and Engels believed that nationalism was a 'false consciousness' Socialism is an internationalist ideology and rejects the concept of nationalism. The point of 'false consciousness' was to stop the international proletariat from uniting and rising up against their (minority) bourgeoisie bosses.
For socialist internationalists, it is possible to build a better world based upon the twin goals of equality and social justice. Nations should work together to create a more peaceful world and finally bring an end to capitalist exploitation. As with other ideologies along the left of the political spectrum, socialist internationalists argue that there is a shared common interest amongst the working-class. Our identity is determined by economic forces rather than artificially-imposed national boundaries.
Later, Lenin re-visited nationalism in his writings on imperialism. In his 1917 booklet imperialism, the Highest Stage of Capitalism, Lenin's premise was that capitalism had avoided collapse (as predicted by Marx) by 'buying off' its indigenous population with proceeds made by exploiting the proletariats in its colonies. This gave the country's own workers improved wages and working conditions while ruthlessly exploiting workers in other countries it controlled. In this way Lenin extended Marx and Engels' analysis of nationalism as being a tool used by capitalism to prevent a proletarian revolution