State socialism is a classification for any socialist political and economic perspective advocating state ownership of the means of production either as a temporary measure in the transition from capitalism to socialism, or as characteristic of socialism itself. It is often used, sometimes interchangeably with state capitalism in reference to the economic systems of Marxist–Leninist states such as the Soviet Union to highlight the role of state planning in these economies, with the critics of said system referring to it more commonly as "state capitalism".Libertarian and democratic socialists claim that these states had only a limited number of socialist characteristics. However, Marxists-Leninists maintain that workers in the Soviet Union and other Marxist-Leninist states had genuine control over the means of production through institutions such as trade unions.
State socialism is held in contrast with libertarian socialism, which rejects the view that socialism can be constructed by using existing state institutions or by governmental policies. By contrast, proponents of state socialism claim that the state, through practical considerations of governing, must play at least a temporary part in building socialism. It is possible to conceive of a democratic state that owns the means of production but is internally organized in a participatory, cooperative fashion, thereby achieving both social ownership of productive property and workplace democracy in day-to-day operations.
The philosophy of state socialism was first explicitly expounded by Ferdinand Lassalle. In contrast to Karl Marx's perspective, Lassalle rejected the concept of the state as a class-based power structure whose main function was to preserve existing class structures; therefore Lassalle also rejected the Marxist view that the state was destined to "wither away". Lassalle considered the state to be an entity independent of class allegiances and as an instrument of justice that would therefore be essential for the achievement of socialism.