Imagine you suddenly find yourself in the control room of a vast technological apparatus, sometime in the future, where you are told that science has satisfied all the needs of all living humans. Furthermore, you learn, the next generation of the species will not be produced in the usual way, but instead by this machine, provided only that somebody push a little red button. The catch: you have to give a reason for pushing it. You hesitate: what do you say? Our own world is more like this scenario than we at first may be inclined to admit, not least in the fact that, mutatis mutandis, we seem to be struggling to come up with a good answer. The problem, says Remi Brague, is fundamentally a metaphysical one. Now, mention of 'metaphysics' in decent society these days is likely to elicit a smile or an unimpressed shrug. If there is a shelf with that label on it in your typical bookstore you are as likely to find guides to crystals, chakras, or hemp care there as you are treatises by Aristotle, Aquinas, or Kant. And, in spite of the ongoing revival of academic interest in metaphysics, it remains a rather specialist domain, a marginal sub-discipline in departments of philosophy, be they analytical or continental in cast. If you should take it too seriously, you'll lose your bearings in the real world, and you'll go adrift in some ethereal sea of dreams. It is, in a word, irrelevant - right? Wrong, Brague writes. Sustained reflection on the nature of being, undertaken in the hope that something can indeed be said about it, was for millennia considered to be among the most important of intellectual pursuits, and not without reason. With his characteristic combination of erudition and wit, Brague takes us on a sweeping tour of the discipline's varying fortunes, from its early Athenian practitioners through its Jewish, Muslim, and Christian heirs, to the chorus of critics who in the last few centuries succeeded in putting an end to its dominance. But the questions that metaphysics was asking, Brague shows, did not disappear with its demise, and so, whether implicitly or explicitly, metaphysics itself has resisted relegation to the history books. For the nature of being, and especially our relationship to it, has continued to haunt its triumphant critics. One quintessentially metaphysical claim above all, as Brague suggests, seems to have horrified them: the doctrine that all that is, insofar as it is, is good. And yet, in rejecting the "convertibility" of the "transcendentals" of being and goodness, critics of the old metaphysics - Voltaire, Kant, Schopenhauer, Nietzsche, Heidegger, Carnap, and Levinas among them - in their own ways offered metaphysical counter-claims, even as they turned increasingly anthropological in their interests. They also raised the stakes. For, whether the denial of the goodness of being can legitimately be attributed some causal responsibility for a world in which our species could rapidly and deliberately ensure its own extinction, this is the world we live in, and that denial does form the basis of the intellectual background from which we tend to begin our speculations. If we need to be able to articulate reasons for our project not to end, then we also need to rethink the rejection that we have come to take for granted. What Brague offers us here is not a narrative of decline, not a Jeremiad, not a nostalgic lament for the thought-world of a bygone era, but a sympathetic outline of some of the major tensions in the philosophical underpinnings of the modernity that we all inhabit. As such, it forms a part of his ongoing effort take modernity "more seriously than it takes itself", to expose its hidden foundations, and to push it to its logical conclusions. In so doing, he hopes to help clarify where it is that we are going as a species, and to ensure that wherever it is, there is room for us humans in it.