In politics, left-wing, leftist, and the Left are terms applied to socially progressive and egalitarian positions. Originally, during the French Revolution, left-wing referred to seating arrangements in parliament; those who sat on the left opposed the monarchy and supported radical reform. The organizers of the First International saw themselves as the successors of the left wing of the French Revolution. In contemporary politics the term left is applied to social liberalism, social democracy, socialism, communism, and most forms of anarchism.
See also: Left-Right politics. In politics the term left wing derives 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 labelled as 'left' before Marxist ideas 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 now considered to be right-wing. A similar phenomenon exists in France, where it is known as sinistrisme.
From mid-19th century, 'left' would increasingly refer to various forms of socialism and communism. Particularly influential was the publication of the Communist Manifesto by Karl Marx and Friedrich Engels in 1848, which asserted that the history of all hitherto existing human society is the history of class struggle. It predicted that a proletarian revolution would eventually overthrow bourgeois society, and by abolishing private property create a classless and stateless and post-monetary society. In the International Workingmen's Association (1864-76), sometimes called the First International, delegates from many different countries, and from many different left-wing political groups and trade union organizations, met together.
The Second International (1888-1916) was eventually divided by the question of supporting or opposing the First World War. Those who opposed the war, such as Lenin and Rosa Luxemburg, saw themselves as further to the left (see Zimmerwald Left). Out of this conflict the socialist movement divided into Social Democrats and Communists, the latter being seen as further to the Left.
In the 1960s with the political upheavals of the Sino-Soviet split and May 1968 in France, thinkers of the 'New Left' viewed themselves as being more critical of Marxist and Marxist-Leninist discourse (labelled the 'Old Left'). Left-libertarian Roderick Long describes left-wing politics as including "concerns for worker empowerment, worry about plutocracy, concerns about feminism and various kinds of social equality.
The meaning of the political terms left, right and centre are relative to a specific context, but in general terms, Left-Wing ranges from communism to social democrat. Center left means a position close to the political mainstream. In several European countries, it describes alliances that encompass both leftist and centrist elements. In French politics, a distinction is made between the left (Socialists and Communists) and the far left (Trotskyists, Maoists, Anarchists). In China, the Chinese New Left denotes a tendency which opposes economic reforms and favours the restoration of socialist policies along Maoist lines. In the Western context, New Left refers to cultural politics, sometimes referred to as identity politics.
Ultra-leftism is a general reference to the politics of the far left. The term hard left is associated with British politicians such as Tony Benn and the Campaign Group and Labour Briefing , as well as Trotskyist groups such as Militant Tendency and Socialist Organiser. While the hard left is strongly influenced by revolutionary Marxism, the soft left has a more gradualist approach to building socialism.
Although specific economic means are not agreed upon by different leftists, almost all of them agree that some form of government or social intervention in the economy is necessary, ranging from Keynesian economics and the welfare state through industrial democracy and the social market to nationalization of the economy and central planning. During the industrial revolution, left-wingers became associated with trade union movements. More recently, leftists have criticized what they perceive as the exploitative nature of globalization, such as sweatshops, the race to the bottom and unjust lay-offs.
Some leftists believe in Marxian economics, which are based on the economic theories of Karl Marx. Some distinguish Marx's economic theories from his political philosophy, arguing that Marx's approach to understanding the economy is intellectually independent of his advocacy of revolutionary socialism or his belief in the inevitability of proletarian revolution.  Marxian economics does not lean entirely upon the works of Marx and other widely known Marxists; it draws from a range of Marxist and non-Marxist sources. Marx defined the proletariat as salaried workers, in contrast to the lumpen proletariat, who he defined as the poorest and outcasts of society, such as beggars, tricksters, entertainers, buskers, criminals and prostitutes. . The political relevance of farmers has divided the left. In Das Kapital, Marx scarcely mentioned the subject.
The question of nationality and nationalism have been central features of political debates on the left. The Marxist social class theory of proletarian internationalism asserts that members of the working class should act in solidarity with working people in other countries due to common class interest, rather than only focusing on their own countries. Proletarian internationalism is summed up in the slogan, "Workers of all countries, unite!", the last line of The Communist Manifesto. Union members learned that more members meant more bargaining power, and taken to an international level, leftists argued that workers ought to act in solidarity to further increase the power of the working class. Proletarian internationalism saw itself as a deterrent against war, because people with a common interest are less likely to take up arms against one another, instead focusing on fighting the ruling class. According to Marxist theory, the antonym of proletarian internationalism is bourgeois nationalism. Left-wing movements therefore have often taken up anti-imperialist positions.
On the other hand, there are strong elements of left-wing nationalism, political tendencies which some link to the pressure generated by economic integration with other countries encouraged by free-trade agreements. This view is sometimes used to justify hostility towards supranational organizations such as the European Union. Left-wing nationalism can also refer to any nationalism emphasizing a working-class populist agenda attempting to overcome perceived exploitation or oppression by other nations. Many Third World anti-colonial movements adopted left-wing and socialist ideas.
The Global Justice Movement, also known as the anti-globalisation or alter-globalization movement, protests against global trade agreements and the negative consequences they perceive them to have for the poor and the environment. This movement is generally characterised as left-wing, though some activists within it reject association with the traditional left. There are also those on the right, Pat Buchanan for example, who oppose globalization on nationalistic grounds. The Global Justice Movement does not oppose globalisation per se, on the contrary, it supports some forms of internationalism). The main themes of the movement are the reforms (or abolition) of international institutions such as the World Bank and the International Monetary Fund, and the creation of an international social and environmental justice movement. It rejects the leadership of any political party, defining itself as a "movement of movements."
See also: List of socialist countries and List of left-wing internationals. The Leninist branch of Marxism argues that a proletarian revolution must be led by a vanguard of professional revolutionaries, men and women who are fully dedicated to the communist cause and who form the nucleus of the communist revolutionary movement. The dictatorship of the proletariat or workers' state are terms used by Marxists to describe what they see as a temporary state between the capitalist and communist society.
Left-wing internationals include dozens of historic and current organizations such as the First International, the Second International, or the Socialist International, World Socialist Movement, and the Revolutionary Internationalist Movement, and the International Conference of Marxist-Leninist Parties and Organizations (Unity & Struggle).
Many early feminists and advocates of women's rights were considered politically radical left-wing by their contemporaries. Feminist pioneers such as Mary Wollstonecraft were influenced by radical thinkers such as Thomas Paine. Many notable leftists have been feminists, such as: Marxists Clara Zetkin and Alexandra Kollontai, Communist Helen Keller, anarchist Emma Goldman and Annie Besant, who was involved in various socialist groups.  
In more recent times the women's liberation movement is closely connected to the New Left and other new social movements that challenged the orthodoxies of the Old Left. Socialist feminism (e.g.Freedom Socialist Party, Radical Women) and Marxist feminism (e.g. Selma James) saw themselves as very much within the left, even though they challenge its male-dominated and sexist structures. Liberal feminism is closely connected with left-liberalism, and the left-wing of mainstream American politics. (e.g. the National Organization for Women). Radical feminism (e.g. Mary Daly) is harder to place on a left-right spectrum; it has more in common with deep ecology, which rejects this axis.
Social progressivism is another common feature of the Left, particularly in the United States, where social progressives advocated the abolition of slavery, women's suffrage, civil rights, and multiculturalism. Progressives have both advocated prohibition legislation and worked towards its repeal. Current positions associated with social progressivism in the West include opposition to the death penalty, legal recognition of same-sex marriage, distribution of contraceptives, public funding of embryonic stem-cell research, and that a woman has the right to undergo an abortion. Public education is a subject of great interest to social progressives, who support higher standards in science and mathematics education, comprehensive sex education, and making condoms available to high school students. Social progressives are also anti-racist.
Third-worldism regards the inequality between developed, or First World countries, and the developing, or Third World countries as of key political importance. It supports national liberation movements against what it takes to be imperialism by capitalist nations. Key figures associated with Third-worldism include Frantz Fanon, Ahmed Ben Bella, Andre Gunder Frank, Samir Amin and Simon Malley. Among the New Left groups associated with Third Worldism were Monthly Review and the New Communist Movement.
Third worldism is closely connected with Pan-Africanism, Pan-Arabism, Maoism, African socialism and Latin American socialist trends. The Palestine Liberation Organization and the Sandinistas are or have been particular causes célèbres. Some left-wing groups in the developing world, such as the Zapatista Army of National Liberation in Mexico, the Abahlali baseMjondolo in South Africa, and the Naxalites in India, argue that the First-World left takes a racist and paternalistic attitude towards liberation movements in the Third-World. There is particular criticism of the role played by NGOs and the assumption by the Western Anti-globalization movement that they should seek to influence the politics of the Third World.
Left-wing postmodernism opposes attempts to supply universal explanatory theories, including Marxism, deriding them as grand narratives. It embraces culture as the battleground for change, rejecting traditional ways of organising, such as political parties and trade unions, and focusing instead upon critiquing or deconstruction. Left-wing critics of post-modernism assert that cultural studies inflates the importance of culture by denying the existence of an independent reality. 
The most famous critique of post-modernism from within the Left was the 1996 prank by physicist 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", in which a mix of mis-stated and mis-used terms from physics are used to support the claim that physical reality does not objectively exist, but is psychologically and politically constructed. Sokal composed a nonsensical article entitled "Transgressing the Boundaries: Toward a Transformative Hermeneutics of Quantum Gravity", The journal Social Text published the paper in its Spring/Summer 1996 issue, whereupon Sokal publicly revealed his hoax. While this action was interpreted as an attack upon leftism, Sokal intended it 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.
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."