Capitalism, Socialism, Is, Ought

Marxism shares with Capitalism a profound methodological confusion--between Descriptive and Normative principles.  Just as Capitalists vacillate between the thesis that Profit-seeking is, as a matter of fact, the fundamental behavioral principle, and it ought to be the fundamental principle, Marxists sometimes posit Socialism as the inevitable Dialectical resultant of the contradictions of Capitalism, and sometimes prescribe Socialism as the cure for Capitalist Exploitation.  Now, clarity regarding a confusion that has sometimes been facilely rendered as the thesis that 'one cannot derive an "ought" from an "is"', can be gained from developing an insight from Hume together with one from Kant.  As the former observes, what 'is the case' is, more precisely, what 'has been the case', and, as the latter posits, there are two 'perspectives' involved.  So, combining them--a Descriptive principle pertains to past events, while a Prescriptive principle pertains to nascent future action.  Thus, not only the latter cannot be derived from the former, the former cannot be 'derived' from the latter via some simple Logical operation, either.  So, Marxism has been deficient in explaining why Capitalist Exploitation should be abolished, and why it should be replaced with Socialism, i. e. deficient in making explicit the Moral principle that it seems to presuppose.