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 Raemi 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. But 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?"--