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.
Marxism
Marxism has developed into many different branches and schools of thought, though now there is no single definitive Marxist theory. Different Marxian schools place a greater emphasis on certain aspects of classical Marxism while rejecting or modifying other aspects. Many schools of thought have sought to combine Marxian concepts and non-Marxian concepts, which has then led to contradictory conclusions. However, lately there is movement toward the recognition that historical materialism and dialectical materialism remains the fundamental aspect of all Marxist schools of thought, which should result in more agreement between different schools.