Much of their work was also seeking to build up a socialist
movement (the International Working Men's Association) which
shared their moral rejection of the exploitative nature of capitalism.
As the Communist Manifesto shows, the theory can be impressively
marshalled as rhetoric to buttress an appeal to political action. The
feeling of being on the side of history, having a ’scientific’ insight into
social processes, and being morally in the right, is a heady brew which still appeals — especially to the young and politically idealistic.