Value-form
The Western Left academics are nowadays very happy to talk about "varieties of capitalism", but talking about "varieties of socialism" remains almost an absolute "no-no". Most Marxists continue to believe in "only one" (Marxian) socialism: either that, or nothing at all. "Either" a society or movement conforms to the true concept of socialism, "or" it does not; and if it does not, it "cannot be" socialism. However, precisely "because" there are many different Marxist beliefs about socialism, Marxists cannot agree among themselves whether Soviet-type societies were socialist, capitalist, or something else. Some countries meet with the moral expectations which Marxists have, and others do not.Originally Marx and Engels themselves had heckled the advocates of "true socialism", but later Friedrich Engels and Karl Kautsky promoted Marxist socialism as the one and true "scientific socialism" within the Socialist International. When he was 43 years old, Lenin stated: "The Marxist doctrine is omnipotent because it is true". Lenin's Communist International (a deliberate split with the social democrats) adopted Marxist socialism as its official political doctrine.
Marxian economics
Marx employed a labour theory of value, which holds that the value of a commodity is the socially necessary labour time invested in it. In this model, capitalists do not pay workers the full value of the commodities they produce; rather, they compensate the worker for the necessary labor only (the worker's wage, which cover only the necessary means of subsistence in order to maintain him working in the present and his family in the future as a group). This necessary labor is necessarily only a fraction of a full working day - the rest, surplus-labor, would be pocketed by the capitalist as profit.