(Original post by Jay Riall)
My question is this - when and where does this differentiation between the two words come from? The books I have read on the history of Marxism do not seem to make this distinction anywhere, some of them also say that Marx and Engels used the words socialism and communism almost interchangeably. What am I missing?
It'd be helpful to know which books you've read which lead you to this conclusion as I'll be able to better explain why they've failed to do so if I appreciate what foundation you've got...
However, to try and tackle this question without that knowledge. As I pointed out in reference to the distinction in the Marxist and Leninist conceptualisations of the "dictatorship of the proletariat", you also have to begin to make distinctions in the influences upon Marx's thought. And so, ladies and gentlemen, let us go back to the beginning.
In the aftermath of the Thermidorian Reaction in 1794 and the death of Maximillien Robespierre, thousands of political prisoners in the gaols of revolutionary France were let out. Amongst them three important gentlemen for our little tale: Babeuf, Saint-Simon, and Fourier. Now these three, in their different ways, exemplify the three competing strands in Marxism and explain also why Marx and Engels settled on the term "communism" for their utopian vision instead of socialism and formulated socialism as a 'lesser' stage.
Babeuf in the aftermath of Thermidor condemned Robespierre for his betrayal of the aims of the revolution and particularly the revolutionaries - the artisans and peasants of France who had helped to make the revolution. Babeuf became one of the very first communists and it is from his reaction to Robespierre that we get the notion of a 'proletarian' revolution.
Saint-Simon, who was much more conservative than his compatriots, considered it to be the neglect of the needs of production and modernity that had let down the revolution. He was, as some historians have called him, the 'heir to the Techno-Jacobins'. From his though Marx garnered the importance of production and economic necessity.
From Fourier, however, he got his Romantic soul. The beating Romantic heart of Communism comes from the reaction of Fourier who felt that the important thing was neither equality nor productivity but pleasure.
Marx, as you can imagine, combined all three of these strands: egalitarian, scientific, and Romantic into a grand theory which is about as coherent as the Liberal Democrats. However, part of the problem of their indifferent use of socialism and communism, I think, lies in what I have to say next.
In someways, from reading the works of Marx, one gets the impression that he considers socialism to be at best a faux-proletarian philosophy. Deep down communism, his melding of the egalitarian, scientific, and Romantic reactions to the Roberpierrian mess, was his invention and the one which he felt the true proletariat would ascribe to. In this way, I think, does socialism become a fairly abused term in Marxism and all the more so after Bernstein's strong, but ultimately fair, attacks on some of the dodgier elements of the overall theory: the Labour theory of value, for example.
The very definite split between socialism and communism came during the Great War with the collapse of the (social democratic) Second International. See, for example, the Zimmerwald and Kiental conferences held in 1915 and 1916. From that point on, and particularly after the Bolshevik Revolution in Russia, the divide between socialism and communism was secured.
I suspect there's more questions you have now but hopefully that answers the initial question you had?