June 20, 2018:
"Materialism" now has a different meaning for Althusser than the traditional ones. Engels and Lenin argued that philosophies are either idealist or materialist, where "idealism" in its broadest sense means that what people think is more important than the physical world they inhabit, and "materialism" means the physical world is in some sense determinant of what people think. In his last works Althusser rejected the duality of the idealism/materialism pair as itself an idealist position reflecting the historical dominance of idealism over materialism in the history of philosophy. He suggested instead that each of the great philosophies contains tendencies toward both idealism and materialism, necessarily, as an effect of the position it occupies in its war against other philosophies: that every philosophy will "occupy" its enemy's positions, to some degree inside itself, in its specific way.
He now defines materialism as a relationship to the dominant idealist tendencies in all of philosophy: materialism is a rejection of all concepts of origins and ends, which are always linked and always dominated by ends: "The question of the origin of anything whatsoever is always posed as a function of the idea one has of its end." A philosophical tendency will be more materialist the more it rejects this speculary trap, and with it all notions of either teleology or meaning.
Althusser's purpose was, I think, to reclaim the centrality of class struggle, which he opposed to the "harmful" metaphysics of universal historical laws. "A truly materialist conception of history implies that we abandon the idea that history is ruled and dominated by laws which it is enough to know and respect in order to triumph over anti-history." A non-metaphysical, non-teleological materialism of singularity and specificity.