How much of previous economics (historically) is still relevant today?
How is it determined?
Is e.g. 18th century economics still relevant today? Is it accurate/useful to cite Adam Smith for example?
It's clear that people still cite e.g. Smith or Marx, but one could question, whether such citing serves a "purposeful" description of contemporary reality or whether it's merely made plausible to "apply Marx today", because one can.