To recap and expand upon the previous post on the basis of "dialectical materialism":
The material world and everything in it is in a conscious state of flux and change, because of its own internal contradictions. The birth of human consciousness offers the possibility of this "dialectical" process being directed by will.
However, the division of human society into rulers and ruled, the partly-conscious and the forcibly-unconscious, hampers and frustrates this possibility. In the capitalist era, it has allowed humanity to call up vast, potentially world-changing powers, but to not have any control over them.
This contradiction can only be solved by those who actually, physically, create and change the world in the modern era - those who work with muscle or brain - becoming conscious and taking control over human society.
Because the world socio-economy is now so vast and complicated, this can only be done on a collective basis from the ground up, with interdependent individuals acting democratically to direct the productive tools at the disposal of the human species. It will also require the forcible removal from power of the capitalist class and the state apparatuses they have set up to protect their privileges.
Now read on...
Why hasn't this happened yet? As we said before, because the other side has all the nuclear bombs and prisons and most of the guns. But that's only part of the question. Most people in a modern capitalist society don't need an armed guard standing over them to keep them in line - they allow themselves to be exploited and obey the irrational laws because they accept that this is the right way to behave. (As an aside, this is the real reason that slavery was abolished - the wage-labour system is a much more effective form of social control, because the man with the gun is usually invisible.)
One of Marx's most vital comments is that the ideology of the ruling class is the ideology of society. Let's use a metaphor of a society having an "infosphere", like a planet has an atmosphere. Every member of a society is constantly and invisibly surrounded by the ideas evolved by that society's rulers to make their own continued rule look not only justified, but the only possible option. Partly this is accomplished deliberately through ideological institutions. In previous eras this was done by churches or other mass organisations - nowadays in advanced capitalist countries, it is done more and more via the mass media.
But it's also because the way the world works makes the lies seem like truth. Because virtually everyone works for some boss in return for wages or salary, it makes sense that that is the natural way to earn a living. Because the system is based on competition and competitive accumulation of wealth, it makes sense that people should have to struggle against each other to survive. Because most people don't have a guy with a gun standing over them to obey the law and behave like good employees, it makes sense that people are doing so out of their own freely arrived at decisions.
When that anonymous Bush Administration staffer made that snide comment about "the reality-based community", this is what he meant. Because ideas come from experience as well as from the TV or from the preacher, whatever they succeed in imposing on us will look not only rational, but natural. People will end up justifying it to themselves just because no credible alternative is presented. In this case, existing reality shapes ideas - but, since in the modern era so much is potentially under human control - the ideas in people's heads determine how much existing reality can be changed.
The Italian revolutionary Antonio Gramsci spent 15 years in Mussolini's jails. At this time, he made the most intelligent comments so far in the Marxist tradition as to how to fight the war for human liberation on the domain of ideology.
Gramsci suggested that everyone's consciousness contains two contradictory elements. Firstly, "common sense" - the ideas they pick up from the "infosphere" of the society around them. Secondly, "good sense" - the ideas that they come to for themselves from their own personal experience. The experience of workers in struggle - that the wagelabour relation is exploitative, that only collective action with other workers can improve their own situation, that - is more sharply counterposed to the "official infosphere" than anyone else's.
Lenin, summing up the insights of dialectical materialism, said "ideas become real forces when they seize the masses". But Gramsci made it clear that the official ideas are "short-circuited" most effectively when proved wrong in practice - that is, in struggle against the ruling power. There's an old joke that embodies this insight: "a radical is a liberal who's been beaten up by a cop".
The problem is that the official structures which systematically pollute the infosphere are getting stronger as more people's experience brings them into conflict with the lies. Our rulers won't use bribery, they prefer not to use force, so lies upon lies are becoming their central weapon. Their technology in this area is approaching a high degree of perfection - anyone who watches Fox News or has read something on "neurolinguistic programming" (aka corporate magic) will understand this. So the central question for Marxists and other world-changing radicals is how to tip the balance between "common sense" and "good sense" in favour of the latter in the minds of the majority - the workers who are in a position to reorient the entire creaking superstructure of human society, if they want to. It's at this point that the concerns of Marxists and of the new generation of occultists - in particular, those embodied in the fledgling Ultraculture movement - coincide. But that's a topic for another post.