Two quotes, taken from personal letters, and included in Emmanuel Terray's Marxism and "Primitive Societies", trans. Mary Klopper (New York and London: Monthly Review Press, 1972); Le Marxisme devant les societies "primitives" (Maspero, 1969). From the essay 'Morgan and Contemporary Anthropology' (5-92).
'In fact, Morgan's "structuralism," like that of his successors, was based on a positivist conception of science in which, to quote Alain Badiou:
The theory is the model, experimentation consists of isolating the empirical correlate which materializes the model; the experimental apparatus [must allow] for a separating effect exhibiting an approximate realization of the form.(p.38)'
'Alain Badiou believes that Marx, on the contrary, believed that:
(p.39)It is impossible to set a theoretical conception of history against real history defined by its very complexity - its empirical impurity. In Marxist epistemology the complexity is constructed according to the concepts of a theory. . . . It is the proper task of a theory of history to give an account of the nature of real society.
Obviously, Badiou in his more Althusserian moment, but I'll leave parsing/explanation to the real experts...