The term 'left' has been used to identify a wide range of political movements, tendencies and thinkers. Ideologies considered part of the left include Progressivism, Social liberalism, Social democracy, Socialism, Syndicalism, Marxism, Communism, Autonomism and most forms of Anarchism.
The term originates from the French Revolution, when radical Montagnard deputies from the Third Estate generally sat to the left of the president's chair, a habit which began in the Estates General of 1789. The moderate Feuillants generally sat to the right. It is still the tradition in the French Assemblée Nationale for the representatives to be seated left-to-right (relative to the Assemblée president) according to their political alignment. In some European countries classical liberals were labeled as 'left' before Marxist thoughts came to define the left. In the case of Denmark and Norway the historical liberal parties still carry the name Venstre (literally meaning 'Left') even though they are right-wing.
From mid-19th century, 'left' would increasingly refer to ideologies advocating various forms of socialism and communism. Particularly influential event was the publication of the Communist Manifesto by Karl Marx and Frederick Engels in 1848. The Manifesto suggested a course of action for a proletarian revolution to overthrow the bourgeois society and abolish private property, which was believed to lead to a classless and stateless society.
Socialist movements emerged across Europe and some countries outside of Europe. The International Workingmen's Association (commonly named the 'Second International') gathered labour parties with a combined membership of millions. During the First World War, the Second International was divided on the question of supporting or opposing the war. The dissident tendency, which included the Russian Bolsheviks of Lenin, Rosa Luxemburg in Germany amongst others, considered themselves as further to the left that the other labour parties (see Zimmerwald Left). Out of this conflict the socialist movement was divided into Social Democrats and Communists, the former category either seen as left or center-left in most countries today whilst the latter are generally seen as leftists in most cases.
In the 1960s with the political upheavals of the Sino-Soviet split and the May 1968 revolt in France, there was an emergence of the 'New Left'. political movements and thinkers that were highly critical of the established Communist movement and traditional Marxist discourse (labelled the 'Old Left').
The terms 'left', 'right' and 'centre' are however contextual terms, relative to the political situation of individual countries and regions. In an article on the 2001 general election in the United Kingdom, the U.S. Washington Post newspaper observed that the healthcare and welfare policies of the British Conservative Party would be on "the far left-wing fringe of American politics".
Center left is a term used to describe refers to a political position that is close to the center of the political mainstream in a particular country. The usage of the term differs widely from country to country. In several European countries, it is a term used for alliances that encompass both leftist and centrist elements.
In France, differentiation is generally made between the 'left' (Socialists and Communists) on one side and the 'far-left' (Trotskyists, Maoists, Anarchists) on the other. Whilst this dichotomy is largely uncontroversial in French politics, the term 'far-left' is used as a pejorative term in Anglo-Saxon politics. In British politics, 'soft left' refers to the moderate sectors of the Labour Party, whereas 'hard left' is a term used to describe the more radical sectors of the party.
The 'New Left' came to embrace egalitarian approaches to cultural politics, including "New Social Movements" based on anti-racism, feminism, environmentalism and LGBT rights. This turn to so-called identity politics has however been decried by organizations of the 'Old Left' as deviations from Marxist understandings of society. In comtemporary Chinese politics, however, the term 'New Left' is used somewhat differently. The Chinese New Left denotes a tendency which opposes economic reforms and in favours of the restoration of socialist policies along Maoist lines.
Some, such as Roger Scruton, reject the notion that green politics is inherently "on the left" arguing (with reference to damage to the environment which occurred in communist regimes such as the USSR) that conservatism is the natural home of conservation. Libertarians argue that people with property rights are more likely to take care of property they own than they are of property held in common. Many Greens however associate the right with free market exploitation of natural resources. When Green politicians have formed political coalitions (most notably in Germany, but also in local governments elsewhere), it has almost always been with groups that classify themselves as on the left. Notable exceptions include Green Parties participating in center-right governments in Mexico, with the National Action Party (PAN); in the 4-party "green-blue" coalition in Finland; and, on March 9 2004 Indulis Emsis of Latvia's Union of Greens and Farmers became the first Green Prime Minister in the world, at the head of a minority center-right coalition.
The Left has traditionally identified itself with the lower classes and with combating oppression. Thus the industrial revolution saw left-wing politics become associated with the conditions and worker's rights in the new industries. This led to build-up of trade union movements. More recently, the left has criticized what it perceives as the exploitative nature by current forms of globalization, e.g. the rise of sweatshops and the "race to the bottom", and either has sought to promote more just forms of globalization, such as fair trade, or has sought to allow nation-states to "delink" or break free of the global economy.
Although specific means of achieving these ends are not agreed upon by different left-wing groups, almost all those on the left agree that some form of government or social intervention in economics is necessary, ranging from Keynesian economics and the welfare state through industrial democracy or the social market to nationalization of the economy and central planning.
Proletarian internationalism also claims itself to be a deterrent against wars amongst nations, because people with a common interest are less likely to take up arms against one another, however they are more likely to do so against the ruling class that Marxists believe oppress workers. According to Marxist theory the antonym of proletarian internationalism is bourgeois nationalism. Leftwing movements have often taken up anti-imperialist positions.
On the other there are strong elements of left-wing nationalism, political tendencies geared to overcoming the losses and disadvantages experienced by a country due to economic pressure or deep integration with another country, often also referring to hostility towards supranational organizations such as the European Union, and free-trade agreements. Left-wing nationalism can also refer to any nationalism emphasizing a working-class populist agenda attempting to overcome economic exploitation or national oppression claimed to be imposed by other nations. During the decolonialization of the Third World countries, many anti-colonial movements adopted leftwing and socialist ideas.
Key figures in the Third Worldist movement include Frantz Fanon, Ahmed Ben Bella, Andre Gunder Frank, Samir Amin and Simon Malley. The New Left led to an explosion of support for Third Worldism, especially after the failure of revolutionary movements in the First World, such as Paris 1968. Among the New Left groups and movements associated with Third Worldism were Monthly Review and the New Communist Movement.
Third worldism is also closely connected to movements such as Pan-Africanism, Pan-Arabism, Maoism, African socialism and Latin American socialist trends. National liberation movements such as the Palestine Liberation Organization, Sandinistas and African National Congress have been causes célèbres of the movement.
Some left-wing groups in the developing world, such as the Zapatista Army of National Liberation in Mexico, Abahlali baseMjondolo in South Africa and the Naxalites in India, argue that the Western left usually takes a racist and paternalistic attitude towards popular movements in dominated countries. There is particular criticism of the role played by NGOs and the assumption by the Anti-globalization movement in Europe and North America that it is a global movement with an automatic right to lead movements in the South.
The most famous critique of post-modernism from within the left came in the form of a 1996 prank by physicist and self-described leftist Alan Sokal. Concerned about what he saw as the increasing prevalence on the left of "a particular kind of nonsense and sloppy thinking… that denies the existence of objective realities, or…downplays their practical relevance…", Sokal composed a nonsensical article entitled "Transgressing the Boundaries: Toward a Transformative Hermeneutics of Quantum Gravity", in which a mix of mis-stated and mis-used terms from physics, postmodernism, literary analysis, and political theory are used to claim that physical reality, and especially gravitation, do not objectively exist, but are psychologically and politically constructed.
The journal Social Text published the paper in its Spring/Summer 1996 issue, whereupon Sokal publicly revealed his hoax. While some saw Sokal as attacking leftism in general, he was very clear that this was intended as a critique from within:
Politically, I'm angered because most (though not all) of this silliness is emanating from the self-proclaimed Left. We're witnessing here a profound historical volte-face. For most of the past two centuries, the Left has been identified with science and against obscurantism… epistemic relativism betrays this worthy heritage and undermines the already fragile prospects for progressive social critique. Theorizing about "the social construction of reality" won't help us find an effective treatment for AIDS or devise strategies for preventing global warming. Nor can we combat false ideas in history, sociology, economics and politics if we reject the notions of truth and falsity.… The results of my little experiment demonstrate, at the very least, that some fashionable sectors of the American academic Left have been getting intellectually lazy.
Traditionalist thinking (conservative) scholar/critics view post-modernism as nihilistic. Gary Jason claims that "The failure of socialism, both empirically and theoretically, ... brought about a crisis of faith among socialists, and Post-modernism is their response.