A monopoly is a hegemonic power relation (unless somebody has changed the meaning of the words when I wasn't looking).
Gurrier, if you think monopoly is interchangeable with hegemonic power relation, do you think the monopolies (in the most broad sense- for instance a monopoly of violence) are unique to capitalism? What Marx does is explain the basis of capitalism, the things that are unique to it that mark it out as a new social system of exploitation which has developed through the class struggle. Your complaint seems to be that what is an explanation of how capitalism functions (in order to destroy it, not to astrologise it), is not an all embracing theory of power relations.
) who studies science and in the bit on methodology it banged on about popper.
errrrrr. He might have been wrong but he definitely had profound things to say. 


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The postulate of falsifiability has been largely done away with inside the scientific community. It's Popperian bollocks, to be frank, and I would suggest a reading of Kuhn or Lakatos, if you want to know how bourgeois scientists dealt with it. The basic critique (Lakatos) is that if everything must be falsifiable, then you're not dealing with science (the study of our surroundings and ourselves) but with logic (or a religion of logic). The fact that capital (and the modern synthesis of evolutionary theory etc.) is impossible to grasp using the pure predicate logic disproves the postulate of falsifiability. The illusion that a theory must be quantifiable in order to be scientific must be one of the more ridiculous comments I've heard. In what way can a science regarding social structuring and entrapment (the critique of political economy) be quantifiable? Where are the quantities? If you think that Marx's theory is about telling us how much profit a company produces, you are way off.