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.
Orthodox Marxism
The philosophy of orthodox Marxism includes the understanding that material development (advances in technology in the productive forces) is the primary agent of change in the structure of society and of human social relations and that social systems and their relations (e.g. feudalism, capitalism and so on) become contradictory and inefficient as the productive forces develop, which results in some form of social revolution arising in response to the mounting contradictions. This revolutionary change is the vehicle for fundamental society-wide changes and ultimately leads to the emergence of new economic systems.