Today, the ideology that best identifies with the notion of the left is socialism, even if this general concept generates, in turn, a galaxy of thought, some of which gravitate decidedly to the right. The saddest example, German National Socialism, is the most extreme form of the right known today.
In that political vision, socialist collectivism was used as a form of extreme defense and exaltation of a national community, defined by racist and exclusionist criteria, in stark contrast with various forms of internationalism, real or presumed: from the Jewish community, accused of acting against the interests of the national community with their capitalist activities, to the socialists, characterized by the struggle of the working class since the age of Karl Marx, according to whom the interests of the working class are not the interests of the nation it lives in, as within the nation is also the enemy, the capitalist owners of the means of production. The interest of the working class is, instead, solidarity with all those who suffer under the same conditions, beyond national boundaries, the proletariat of the world.
From the very beginning, the workers’ movement attempted to create an international representation and to coordinate the policy of all the affiliated parties with a central body. Founded in 1951, the Socialist International fulfills this role, even if some of the world’s most important affiliate parties (from England, Germany and France) left in 2013, founding the Progressive Alliance. However, problems in defining a common voice for the cause of the working class existed far before the SI, starting with the First International, the Workingmen's Association, that in 1872, divided into two groups, authoritarian Marxists and anarchic libertarians, disbanding four years later.
The most significant experience was that of the Second International, established in 1889, bringing together forces of Marxist and Labourist inspiration. In contrast with Marxists – the dominant force in the new organization – who aimed to overthrow the old political order through revolution or reform, Labourists (mostly English) and Possibilists (in France) aimed to obtain concrete results for the working man through unions, without necessarily entering in the political sphere.