I've done this one before but it really is shameful when self-described Marxists try and play the inscrutability game. How can socialists who've not had the dubious benefit of "professional" philosophical training access important theoretical issues when writers insist on applying the technical vocabulary with a trowel? The below comes from the English translation of Sebastiano Timpanaro's On Materialism and was published when Althusser-speak was all the rage in academic Marxist circles, so there's your context.
Generally, its point of departure are real and serious problems in the epistemology of the sciences, related to the need for a re-examination of the very foundations of scientific knowledge. But this epistemological crisis is quickly used in order to reassert an absolute, mythological creativity and freedom belonging to man, and in order to be able to disregard both the real conditioning to which man is subject and the way to overcome it. It then becomes possible to proclaim a completely rhetorical and mystifying subjectivism-voluntarism (p.123).According to this obituary by Perry Anderson our Seb was "one of the purest and most original minds of the second half of the century." Pity more than a few will have been put off by his impenetrable prose.