Ah, abstraction! Now you're talking. This is what I teach
(taught) my students: The basic abstraction of bourgeois
economics is "economic man." Such a thing never existed.
This method of "make believe" derives from Hobbes' abstraction,
the "state of nature," which, in turn, he gets from Gallileo's
concept of "frictionless movement." Science is filled with
similar make-believes, e.g., the "perfect vacuum." There is
a close link, then, between the method of western science and that
of economics. Marx's abstraction is not to make up something
as an apriori premise, but to abstract certain social relations
from the totality of relations for intensive investigation.
Capital I abstracts the capital/labor relation in production
(where SV is produced) from other capitalist relations (e.g.,
circulation relations). Why this particular relation? Because,
according to the materialist conception of history, the mode
of extraction of surplus labor (mode of imposition of labor;
production of surplus product; appropriation of surplus product
by owning/ruling classes; utilization of surplus product by
these classes) is the key to understanding the dynamics of any
particular mode of production. I.e., in the process of
production, etc., of SV one finds the rudimentary contradiction
of any mode -- the contradiction between forces and relations
of production (content and form, if you like).
My dear friend Bertell Ohlman, who urges me to study his book
on methods of abstraction, thinks the above is a bit crude,
but serviceable for "economists."
Jim O'Connor