Socialism is an economic ideology and political philosophy encompassing diverse economic and social systems: "Socialism may be defined as movements for social ownership and control of the economy. It is this idea that is the common element found in the many forms of socialism." characterised by social ownership of the means of production,*: "Socialism may be defined as movements for social ownership and control of the economy. It is this idea that is the common element found in the many forms of socialism." : "What else does a socialist economic system involve? Those who favor socialism generally speak of social ownership, social control, or socialization of the means of production as the distinctive positive feature of a socialist economic system." : "Just as private ownership defines capitalism, social ownership defines socialism. The essential characteristic of socialism in theory is that it destroys social hierarchies, and therefore leads to a politically and economically egalitarian society. Two closely related consequences follow. First, every individual is entitled to an equal ownership share that earns an aliquot part of the total social dividend ... Second, in order to eliminate social hierarchy in the workplace, enterprises are run by those employed, and not by the representatives of private or state capital. Thus, the well-known historical tendency of the divorce between ownership and management is brought to an end. The society — i.e. every individual equally — owns capital and those who work are entitled to manage their own economic affairs." : "Socialism is an economic system characterised by state or collective ownership of the means of production, land, and capital."; : "Socialist systems are those regimes based on the economic and political theory of socialism, which advocates public ownership and cooperative management of the means of production and allocation of resources." : "Pure socialism is defined as a system wherein all of the means of production are owned and run by the government and/or cooperative, nonprofit groups." : "This alteration in the relationship between economy and politics is evident in the very definition of a socialist economic system. The basic characteristic of such a system is generally reckoned to be the predominance of the social ownership of the means of production." as opposed to private ownership. It describes the economic, political, and social theories and movements associated with the implementation of such systems. Social ownership can take various forms, including public, community, collective, cooperative,: "Socialist systems are those regimes based on the economic and political theory of socialism, which advocates public ownership and cooperative management of the means of production and allocation of resources." or employee.: "Just as private ownership defines capitalism, social ownership defines socialism. The essential characteristic of socialism in theory is that it destroys social hierarchies, and therefore leads to a politically and economically egalitarian society. Two closely related consequences follow. First, every individual is entitled to an equal ownership share that earns an aliquot part of the total social dividend ... Second, in order to eliminate social hierarchy in the workplace, enterprises are run by those employed, and not by the representatives of private or state capital. Thus, the well-known historical tendency of the divorce between ownership and management is brought to an end. The society — i.e. every individual equally — owns capital and those who work are entitled to manage their own economic affairs." As one of the main ideologies on the political spectrum, socialism is the standard left-wing ideology in most countries. Types of socialism vary based on the role of markets and planning in resource allocation, and the structure of management in organizations.
Socialist systems are divided into non-market and market forms.: "socialism would function without capitalist economic categories—such as money, prices, interest, profits and rent—and thus would function according to laws other than those described by current economic science. While some socialists recognised the need for money and prices at least during the transition from capitalism to socialism, socialists more commonly believed that the socialist economy would soon administratively mobilise the economy in physical units without the use of prices or money."; : "Especially before the 1930s, many socialists and anti-socialists implicitly accepted some form of the following for the incompatibility of state-owned industry and factor markets. A market transaction is an exchange of property titles between two independent transactors. Thus internal market exchanges cease when all of industry is brought into the ownership of a single entity, whether the state or some other organization, ... the discussion applies equally to any form of social or community ownership, where the owning entity is conceived as a single organization or administration."; : "Marxian socialism is often identified with the call to organize economic activity on a nonmarket basis."; : "More fundamentally, a socialist society must be one in which the economy is run on the principle of the direct satisfaction of human needs. ... Exchange-value, prices and so money are goals in themselves in a capitalist society or in any market. There is no necessary connection between the accumulation of capital or sums of money and human welfare. Under conditions of backwardness, the spur of money and the accumulation of wealth has led to a massive growth in industry and technology. ... It seems an odd argument to say that a capitalist will only be efficient in producing use-value of a good quality when trying to make more money than the next capitalist. It would seem easier to rely on the planning of use-values in a rational way, which because there is no duplication, would be produced more cheaply and be of a higher quality." A non-market socialist system seeks to eliminate the perceived inefficiencies, irrationalities, unpredictability, and crises that socialists traditionally associate with capital accumulation and the profit system.: "Under socialism, by definition, it (private property and factor markets) would be eliminated. There would then be something like 'scientific management', 'the science of socially organized production', but it would not be economics."; : "This understanding of socialism was held not just by revolutionary Marxist socialists but also by evolutionary socialists, Christian socialists, and even anarchists. At that time, there was also wide agreement about the basic institutions of the future socialist system: public ownership instead of private ownership of the means of production, economic planning instead of market forces, production for use instead of for profit."; : "Socialism has historically been committed to the improvement of people's material standards of living. Indeed, in earlier days many socialists saw the promotion of improving material living standards as the primary basis for socialism's claim to superiority over capitalism, for socialism was to overcome the irrationality and inefficiency seen as endemic to a capitalist system of economic organization."; : "Socialism is a system based upon de facto public or social ownership of the means of production, the abolition of a hierarchical division of labor in the enterprise, a consciously organized social division of labor. Under socialism, money, competitive pricing, and profit-loss accounting would be destroyed." Market socialism retains the use of monetary prices, factor markets and sometimes the profit motive. As a political force, socialist parties and ideas exercise varying degrees of power and influence, heading national governments in several countries. Socialist politics have been internationalist and nationalist; organised through political parties and opposed to party politics; at times overlapping with trade unions and other times independent and critical of them, and present in industrialised and developing nations.: "In fact, socialism has been both centralist and local; organized from above and built from below; visionary and pragmatic; revolutionary and reformist; anti-state and statist; internationalist and nationalist; harnessed to political parties and shunning them; an outgrowth of trade unionism and independent of it; a feature of rich industrialized countries and poor peasant-based communities." Social democracy originated within the socialist movement, supporting economic and social interventions to promote social justice. While retaining socialism as a long-term goal,: "The long term and the short term."; : "Over the long term, however, democratizing Sweden's political system was seen to be important not merely as a means but also as an end in itself. Achieving democracy was crucial not only because it would increase the power of the SAP in the Swedish political system but also because it was the form socialism would take once it arrived. Political, economic, and social equality went hand in hand, according to the SAP, and were all equally important characteristics of the future socialist society."; ; : "... Giorgio Napolitano launched a medium-term programme, 'which tended to justify the governmental deflationary policies, and asked for the understanding of the workers, since any economic recovery would be linked with the long-term goal of an advance towards democratic socialism'"; in the post-war period social democracy embraced a mixed economy based on Keynesianism within a predominantly developed capitalist market economy and liberal democratic polity that expands state intervention to include income redistribution, regulation, and a welfare state.: "Social democracy refers to a political tendency resting on three fundamental features: (1) democracy (e.g., equal rights to vote and form parties), (2) an economy partly regulated by the state (e.g., through Keynesianism), and (3) a welfare state offering social support to those in need (e.g., equal rights to education, health service, employment and pensions)."
The socialist political movement includes political philosophies that originated in the revolutionary movements of the mid-to-late 18th century and out of concern for the social problems that socialists associated with capitalism. By the late 19th century, after the work of Karl Marx and his collaborator Friedrich Engels, socialism had come to signify anti-capitalism and advocacy for a post-capitalist system based on some form of social ownership of the means of production. By the early 1920s, communism and social democracy had become the two dominant political tendencies within the international socialist movement,: "Chapter 1 looks at the foundations of the doctrine by examining the contribution made by various traditions of socialism in the period between the early 19th century and the aftermath of the First World War. The two forms that emerged as dominant by the early 1920s were social democracy and communism." with socialism itself becoming the most influential secular movement of the 20th century. Many socialists also adopted the causes of other social movements, such as feminism, environmentalism, and progressivism.