Marx is postulating the proletarian social revolution as the end of history. He does so because the proletariat is the first revolutionary class in history which lacks social property.
By revolutionary class here we mean a class embodying a new set of relations of production (social behaviours) that will unfetter the productive forces (capacities of society to do things with things.). The proletariat is a revolutionary class because it produces love and solidarity in communal behaviour, a new potential social behaviour around doing things.
The proletariat lacks a purported future form of social property. Their alienation in production and their sale of labour power mean that they don’t have a new way of dividing property up after a revolution. They seek to abolish property as such, because their relationship to their only saleable thing, their labour power, is to abolish the sale of labour power.
In contrast past revolutionary classes such as the bourgeoisie had a new form of social property ready to go: the value-form. Past revolutions sought to justify themselves based on past events. The US planter and mercantile bourgeois looked to Rome. Wat Tyler and Cromwell looked to ancient freedoms. Marx uses slightly different examples:
Men make their own history, but they do not make it as they please; they do not make it under self-selected circumstances, but under circumstances existing already, given and transmitted from the past. The tradition of all dead generations weighs like a nightmare on the brains of the living. And just as they seem to be occupied with revolutionizing themselves and things, creating something that did not exist before, precisely in such epochs of revolutionary crisis they anxiously conjure up the spirits of the past to their service, borrowing from them names, battle slogans, and costumes in order to present this new scene in world history in time-honored disguise and borrowed language. Thus Luther put on the mask of the Apostle Paul, the Revolution of 1789-1814 draped itself alternately in the guise of the Roman Republic and the Roman Empire, and the Revolution of 1848 knew nothing better to do than to parody, now 1789, now the revolutionary tradition of 1793-95. In like manner, the beginner who has learned a new language always translates it back into his mother tongue, but he assimilates the spirit of the new language and expresses himself freely in it only when he moves in it without recalling the old and when he forgets his native tongue.
When we think about this conjuring up of the dead of world history, a salient difference reveals itself. Camille Desmoulins, Danton, Robespierre, St. Just, Napoleon, the heroes as well as the parties and the masses of the old French Revolution, performed the task of their time – that of unchaining and establishing modern bourgeois society – in Roman costumes and with Roman phrases. The first one destroyed the feudal foundation and cut off the feudal heads that had grown on it. The other created inside France the only conditions under which free competition could be developed, parceled-out land properly used, and the unfettered productive power of the nation employed; and beyond the French borders it swept away feudal institutions everywhere, to provide, as far as necessary, bourgeois society in France with an appropriate up-to-date environment on the European continent. Once the new social formation was established, the antediluvian colossi disappeared and with them also the resurrected Romanism – the Brutuses, the Gracchi, the publicolas, the tribunes, the senators, and Caesar himself. Bourgeois society in its sober reality bred its own true interpreters and spokesmen in the Says, Cousins, Royer-Collards, Benjamin Constants, and Guizots; its real military leaders sat behind the office desk and the hog-headed Louis XVIII was its political chief. Entirely absorbed in the production of wealth and in peaceful competitive struggle, it no longer remembered that the ghosts of the Roman period had watched over its cradle. (18 Brumaire)
As the proletariat has a world to win, and only chains in the past, Marx as a good liberal is calling for them to produce a new poetry for the future, and let the squabbles of past societies and failed revolutions lay in the ground. This is liberal as Marx is appealing for a change in social consciousness to produce a change in social being—he has turned his general mode of argument on its head. The idea of Marx being a bad Marxist is explored at depth in the critique of “young” versus “mature” Marx as explored by Althusser for example. An appeal to cultural consciousness (as opposed to class consciousness in praxis) is idealist and not “scientific socialism,” for these critics.
Marx calling for a new poetry all sounds a bit high falutin’ to me, especially considering Engel’s work on past social conflicts as history as motivating ideology for proles (Peasants war; Family, Private property and the state). Given that 1919 is around the corner, I’m sure the bolsheviks and councilists are going to exhibit Rosa Luxemburg once again to shame the purportedly revolutionary left social democrats whose forebears allied with fascists to crush the German Revolution. That even the most “ideologically rigorous materialists,” of the communist movement are effectively historical Live Action Role Players, digging up the reverend dead to exhibit them for political effect. Dragging Rosa from her grave to exhibit her is an appeal to cultural consciousnesses, not to living class struggle. Bolsheviks and council communists both pride themselves on their more historical materialist position than “liberal” or “idealist” social democrats. Yet they’re using the past dead to try to motivate revolution. Either they’re bourgeois revolutionaries, just like Marx himself is; or, Marx is wrong in 18 Brumaire on the uniquely futurist manifesto of proletarian revolution; or, “Why not have both?” (Old el Paso (c.2009))