Precisely because Marx was convinced that the cause of the proletariat was of decisive importance for the whole future of mankind, he wanted to create for that cause not a flimsy platform of rhetorical invective or wishful thinking, but the rock-like foundation of scientific truth.
Capitalism subordinates men to machines instead of using machines to liberate men from the burden of mechanical and repetitive work. it subordinates all, inherent in every commodity, fully unfolds itself in this contradictory nature of capitalist machinery. When capitalism is not overthrown once it has created the material and social preconditions for a classless society of associated producers, this contradiction implies the possibility of a steadily increasing transformation of the forces of production into forces of destruction, in the most literal sense of the word: not only forces of destruction of wealth (crises and wars), of human wealth and human happiness, but also forces of destruction of life tout court.
In fact, it would be very easy to ‘prove’ Marx’s analysis to have been wrong, if experience had shown, for example, that the more capitalist industry develops, the smaller and smaller the average factory becomes, the less it depends upon new technology, the more its capital is supplied by the workers themselves, the more workers become owners of their factories, the less the part of wages taken by consumer goods becomes (and the greater becomes the part of wages used for buying the workers’ own means of production). If, in addition, there had been decades without economic fluctuations and a full-scale disappearance of trade unions and employers’ associations (all flowing from the disappearance of contradictions between Capital and Labour, inasmuch as workers increasingly become the controllers of their own means and conditions of production), then one could indeed say that Capital was so much rubbish and had dismally failed to predict what would happen in the real capitalist world a century after its publication.