The problem of the principle of reason/ground is architectonic. As such it is the great theme of modern philosophy: how and where to begin? The two classical answers are provided by romanticism and enlightenment thinking. If there is a romantic side to Heidegger, as Deleuze says, then Meillassoux inherits and continues a long-standing tradition of enlightenment. Whereas the first always looks for a foundation or ground, even if it turns out be an abyss, the critical reason of the latter rabidly dismantles all grounds. Alternatively, Deleuze calls for a third answer which he calls modernism or constructivism and which always begins by the milieu (par le milieu). Instead of rising out of first principles like a tree from its roots, his metaphysics proliferates like a rhizome, never straying far from the events at the surface in a groping experimentation with the conditions of real experience. For Deleuze, the milieu is not the solid ground on which we stand, but neither is it an abyss or a void. Rather it is the fluctuating ground in which we must learn to swim. It is the element of the problematic as such, an element that matters and calls for an ethics of life. To think by the milieu means to think both without reference to a fixed ground yet also without separating thought from the forces it requires to exist. Whereas Meillassoux reinstalls the Kantian tribunal of reason and the generality of its judgments, Deleuze always emphasizes his own conditions of enunciation, i.e. the matters of concern that enable him to learn. While the anti-correlationist position is one of right, Deleuze’s own position is always one of fact.
A more nuanced criticism of Deleuze than that of Meillassoux, i.e. one that includes the ethical or practical import of his Principle of Sufficient Reason, is put forward by Reza Negarestani, who agrees with Deleuze that ontology is the science of cruelty whilst adding that the univocity of being should be abandoned in favor of a universal void on which any intensive course of unilateral distinction remains dependent (equivocal inexistence): Philosophy of cruelty explains ontological determinations in terms of sadistic (imperative) and masochistic (contractual) bondages to that which does not belong to being, i.e., the problematic chains to the void. In order for the ethics of justice to confront the problems and conditions associated with ontological determinations ourselves and our world it must tread through such problematical fields which are equivocally determined by the void and the ontological medium. The philosophy of cruelty, in this sense, inaugurates the opportunities of grounding ethics on a new definition of being unshackled from the priority of its ontological necessity and mobilized by its chains to that which is exterior to it – the universal.