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
There have been a number of criticisms of orthodox Marxism from within the socialist movement. From the 1890s during the Second International, Eduard Bernstein and others developed a position known as revisionism, which sought to revise Marx's views based on the idea that the progressive development of capitalism and the extension of democracy meant that gradual, parliamentary reform could achieve socialism. This view was contested by orthodox Marxists such as Kautsky as well as by the young Georg Lukacs, who in 1919 clarified the definition of orthodox Marxism as thus: [O]rthodoxy refers exclusively to method. It is the scientific conviction that dialectical materialism is the road to truth and that its methods can be developed, expanded and deepened only along the lines laid down by its founders. It is the conviction, moreover, that all attempts to surpass or 'improve' it have led and must lead to over-simplification, triviality and eclecticism.