David Cameron has quipped that Ed Milband is living in a Marxist universe - which says more perhaps about the ideologically blinked perspective of our Prime Minister than the beliefs of the leader of the opposition.
You don't have to be a Marxist to believe that energy companies are overcharging us. After all former Tory PM John Major has said just this and he is not exactly an out-and-out communist.
In Cameron's free-market universe the stars and planets would be up for sale and no doubt molecules would only react with each other if paid a profit incentive.
However it is worth asking whether Marx should influence our political perspectives today.
Perhaps unusually, unlike Miliband, I am happy to call myself a Marxist.
In British politics this seems rather shocking, like admitting to consuming fried Mars bars or enjoying the music of Barry Manilow.
Marx famously remarked that he wasn't a Marxist and his views have been under serious attack pretty much from when he was exiled from Germany in the 1840s to today.
So is he still relevant and what can those of us on the left learn from him today?
As a Green I became interested in the cause of environmental problems. So many of them are products of capitalism and the theorist who explained capitalism best remains, in my view, the German guy with the beard.
Even right-wing economic commentators from the Economist magazine to the Austrian economist Schumpter have acknowledged - grudgingly - his power in this regard.
Marx and Engels in the Communist Manifesto wrote that history was the history of class struggle. This is a vital insight.
The rich and the powerful continue to work for their own interests. Whether we are discussing the bedroom tax or the assault on Iraq by the US and British governments, class interests remain significant in shaping politics.
The mass of us are, despite sociological debates, members of the working class. We are excluded from owning the means of production and have to work for others, the capitalists, who get fat on the use of our surplus labour power.
Marx was a key ecological theorist. He and Engels were concerned with issues such as deforestation, soil erosion, food additives and river pollution.
In fact one of the best statements of what green politics means can be found in volume III of Capital: "Even an entire society, a nation, or all simultaneously existing societies taken together, are not the owners of the earth. They are simply its possessors, its beneficiaries, and have to bequeath it in an improved state to succeeding generations as boni patres familias (good heads of the household)."
His ecological ideas, which may surprise those who believe he was a prophet of unlimited industrial growth, have been explored in some detail in John Bellamy Foster's book Marx's Ecology. I highly recommend it.
There are other virtues to Marx. He wrote with flair and drew upon a rich literature. He was fascinated by science, history, indigenous peoples and worked obsessively to research his key themes.
I think, above all, he opened up a new way of thinking about politics and society. We are used to political parties and thinkers who draw up often somewhat abstract sets of demands for what they are "for" and what they are "against."
Marx didn't believe the key task was to paint a picture of a better world and challenge the vision of others. This was partly because he was a radical democrat, and knew that one person's vision might be oppressive to others - democratic discussion was necessary.
He also thought that it was important to understand social processes so that we could revolutionise society, rather than list how we would like to see things and why we disagree with others.
This is where his ideas are most enduring. If we understand processes such as the accumulation of capital and the creation of the state, we can potentially enact radical and positive change.
In this sense he and Engels were social scientists. While this seems a little abstract, I once read that Marx saw the world, like Shakespeare, as a theatre.
We often believe that appearances reflect reality, so when the government states that it acts in our interest we might naively believe them. Or we might view society as a conspiracy controlled by a hidden elite.
Marx, while conscious of class power, was aware that social processes shaped even what the ruling class does. Capitalism is more complex than a simple conspiracy from Marx's perspective.
We live perhaps as Brecht, the Marxist playwright suggested, in a theatre, but we can if we understand the processes of creating the dramatic illusion, such as the lighting, the set design and the script-writing we can create our own world rather than being puppets controlled by "extra-human" mechanisms.
Marx noted sagely that "if essences and appearances coincided" there would be no need for "science." For Marx social reality is neither a reflection of reality nor the product of a conspiracy. We need to dig a little if we are to understand it.
Capitalism is about the accumulation of capital.
We forget that human beings create capitalism and we often worship finance.
Stock market values are on the news. The material and emotional needs of human beings are not worth discussing.
Marx pointed to the possibility of a revolution that would put human beings back in control. Above all, he believed in the democratic control of the ownership of production. Rather than the economy being in the hands of a minority, driven by short-term considerations of profit, it should be shared by all.
Marx never claimed to have all the answers. Neither was he always right - for example, Che Guevara pointed out that Marx's criticism of the Latin American anti-imperialist leader Simon Bolivar, whom Marx condemned as a dictator, was open to challenge. His record as a feminist is also worth debating.
Marx's work nonetheless, as even his critics, acknowledge, remains a powerful form of analysis.
Even on the left excuses are used to dismiss Marx's work. However whether one is critical of countries that have tried to put his ideas into practice or the practices of existing Marxist political parties, I think we do still live in a Marxist universe.
Capitalism is after all still with us, inequality is rising and ecological problems are pressing.
We can use his ideas in a dogmatic or sectarian way but this is a mistake. Writing about his ideas and other important Marxist thinkers as a purely academic exercise is also wrong - Marx believed in social change not intellectual activity for its own sake.
Happily Marx's works are available for free, on the Marxist Internet Archive (www.marxists.org) which he would have loved.
And across the world, but especially in Latin America, grass-roots movements are inspired by his work.
Marx remains worth engaging with and on the big questions of reaching a truly democratic and ecologically sustainable society, I am sure I am not alone in finding his work essential.
And I think I need to go to the chip shop for another fried confectionery product. As a cyclist with the winter drawing in I need every calorie I can get.
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