In the Lives of eminent philosophers, the ancient biographer Diogenes Laertius writes that when the work of Heraclitus was first brought to Greece, the owner of the book warned that it required a Delian diver not to be drowned in it. In my thesis, I have chosen Gilles Deleuze and Félix Guattari as my two Delian divers. By means of a comparative study, I hope to have presented a somewhat systematic reading of a number of Heraclitus’ Fragments and of the tenth chapter of A Thousand Plateaus, ‘1730: Becoming-intense, becoming-animal, becoming-imperceptible…’. That is what I have done; why I have done this is because I think that in spite of its alleged downfall, a millennia-long tradition of Western metaphysics is not easily dissolved. Are we not left with an ontology that pretends not to be an ontology? And because metaphysics is concerned with every body and every thing, that is, with πάντα, one may conclude that metaphysics concerns everyone. Accordingly, I have written an introduction to metaphysics in which I wish to show what I think metaphysics is, what it means and what is at stake.