“It is here that, in order to specify the meaning of materialism, we should apply Lacan’s formulas of sexuation: there is a fundamental difference between the assertion “everything is matter”(which relies on its constitutive exception – in the case of Lenin who, in Materialism and Empiriocriticism, falls into this trap, the very position of enunciation of the subect whose mind “reflects” matter) and the assertion “there is nothing which is not matter” (which, with its other side, “not-All is matter”opens up the space for the account of immaterial phenomena). This means that a truly radical materialism is by definition nonreductionist: far from claiming that “everything is matter,” it confers upon “immaterial” phenomena a specific positive nonbeing.” (Zizek, The Parallax View, 168)
“In Descartes, we find an intuition of the same order regarding the ontological status of truths. We know that Descartes gives the name of ‘substance’ to the general form of being as really existing. ‘What there is’ is substance. Every ‘thing’ is substance it is figure and movement in extended substance; it is idea in thinking substance. This is why Descartes’s doctrine is commonly identified with dualism: the substantial ‘there is’ is divided into thought and extension, which in man means: soul and body.
Nevertheless, in paragraph 48 of the Principles of Philosophy, we see that substance dualism is subordinated to a more fundamental distinction. This distinction is the one between things (what there is, that is to say substance, either thinking or extended) and truths.
I distinguish everything that falls under our cognition into two genera: the first contains all the things endowed with some existence, and the other all the truths that are nothing outside of our thought
What a remarkable text! It recognizes the wholly exceptional, ontological and logical status of truths. Truths are without existence. Is that to say they do not exist at all? far from it. Truths have no substantial existence. That is how we must understand the declaration that they ‘are nothing outside of our thought’.” (Badiou, Logic of Worlds, 6)