The subtitle of Frank Ruda’s book in defense of Badiou, Idealism without Idealism, points in the right direction: the predominant philosophical struggle occurs today within materialism, between democratic and dialectical materialism— and what characterizes dialectical materialism is precisely that it incorporates the idealist legacy, against vulgar democratic materialism in all its guises, from scientist naturalism to the post-Deleuzian assertion of spiritualized “vibrant” matter. Dialectical materialism is, first, a materialism without matter, without the metaphysical notion of matter as a full substantial entity— in dialectical materialism, matter “disappears” in a set of purely formal relations. Second, despite being materialism without matter , it is not idealism without an idea— it is a materialism with an Idea, an assertion of the eternal Idea outside the space of idealism. In contrast to idealism, whose problem is how to explain temporal finite reality if our starting point is the eternal order of Ideas, materialism’s problem is how to explain the rise of an eternal Idea out of the activity of people caught in a finite historical situation.
– Slavoj Zizek, Absolute Recoil: Towards A New Foundation Of Dialectical Materialism (pp. 72-73).