E.J. Lowe on the Inescapability of Metaphysics

"How is it possible for creatures like us to chart the realm of possibilities? Of course, this is a curious question, to the extent that it is, itself, a question -- addressed to ourselves -- about the very realm of possibilities, access to which, by us, is being put in question.  Suppose, however, that we were to come up with an argument whose conclusion was that it is not possible for us to chart the realm of possibilities. That conclusion would seem to undermine itself, because the conclusion itself concerns the realm of possibilities, maintaining that that realm does not include the possibility of our charting it.  We could thus only have reason to believe the conclusion if the conclusion were false: so we can have no reason to believe it.  Is this just a trick? I don't think so; rather, it is yet another example of the unavoidability of metaphysics. As rational beings, we cannot but consider ourselves capable of knowing at least something about the realm of possibilities. This should not be surprising. Reasoning itself depends upon a grasp of possibilities, because a valid argument is one in which it is not possible for the conclusion to be false if the premises are true -- and a rational being is a creature which can discern the validity of at least some arguments." -- p.137 of 'Metaphysical Knowledge', in Matthew Haug (ed.) Philosophical Methodology: The Armchair or the Laboratory?