Reality has hit some commentators between the eyes and has forced them to partially recognise Marx's analysis of the nature of capitalist crises which, he explained, were intrinsic to the system.
Capitalism is a cyclical system: crises can be triggered by a number of factors, such as financial crashes or political unrest.
However, the underlying reasons for crisis are the fundamental contradictions of capitalism as first described by Marx.
These include the antagonism between the social, collective nature of production on the one hand, and private ownership of the means of production on the other; and the antagonism between the world market and the limitations of the nation state.
Capitalism is based on production for profit and not for social need. The working class creates new value but receives only a portion of that new value back as wages.
The capitalists take the rest - the surplus. As a result, the working class collectively cannot afford to buy back all the goods it produces.
The capitalists partially solve this by ploughing a proportion of the surplus back into industry, but this results in the production of more goods which, at a certain point, actually intensifies the problem.
The inevitable results are crises of overproduction and overcapacity. In the long term, the capitalists cannot overcome this problem. As a result, capitalism is a system riven by crisis.
While some commentators have accepted that Marx predicted the fundamental features of the modern economy remarkably well, in general they shy away from the conclusions that he drew. Marx famously declared:
"Philosophers have only interpreted the world, the point, however, is to change it."
This does not mean that Marx saw nothing positive in capitalism. He recognised that capitalism, despite all its brutality, played a necessary historic role in developing the productive forces and the world market. It was therefore an advance from the feudal societies that preceded it.
Today, the idea of capitalism as a progressive force is unthinkable to most of those involved in the anti-capitalist movement.
Yet capitalism has developed the world market and the enormous wealth, science and technique that have laid the foundations for a socialist society.
Under capitalism, however, wealth and power have always been concentrated in the hands of a minority - the capitalists.
And the development of technology is not driven by any rational means but by the need for profit. Capitalism is completely incapable of fully harnessing the productive forces it has brought into being.
This is a system where science and technique are only ever used partially and inadequately. And the anarchy of the capitalist market always results in increasing wealth and power for a few alongside poverty for the many.
The strength of the British working class remains immense. The London Underground and rail strikes have given a glimpse of how capitalism can be paralysed when a key section of workers takes action.
Even less powerful sections of workers are able to have an effect on the profits of the capitalists. For example, to a far greater degree than in the past, if teachers were to take national strike action millions of parents would be unable to work because of childcare commitments. This would exert real pressure on the capitalist class.
This does not mean that everything Marx and Engels wrote in the 19th century was correct in every detail or has been confirmed by events.
On timing and the proximity of the socialist revolution and on some other issues they were mistaken.
Many of the demands drawn up in 1848 are now obsolete. Moreover, society today is in many ways very different to then.
Nonetheless, an amazing amount of what they formulated about society is as relevant today as when it was written.