This book follows from another, Truth and Genesis, which identi- fied the Deleuzian enterprise, as it is formulated in Difference and Repetition, with ontogenesis. Genesis, I argued, especially as exemplified in contemporary science, is precisely the aspect of being that Heidegger, in whose thought of the ontological difference the book as a whole is anchored, failed to thematise. Genesis signals the possibility of a genuine compatibility between ontology and science. The other key concept, truth, signalled the side or aspect of being that is irreducible to genesis, the Open (or difference) as such, to which philosophical thought, but also literature and art, respond. Truth and Genesis ends with a claim regarding the compatibility, and even the necessary link, between the two concepts, the two ‘ways’ of being, or nature. With respect to Deleuze himself, and to the extent that, from his thought as a whole, I had extracted only one of the ways of being, I needed to find out whether his ontology also contains elements that could relate to what, following Heidegger, I have called truth, or whether such an ontology is entirely confined to the project of ontogenesis. This book is the result of such a question. It claims that Deleuze's ontology indeed exceeds the boundaries of ontogenesis, and so confirms the intuition that governed Truth and Genesis, albeit with a different vocabulary.