Aristotle on Metaphysics(2004) - Bibotu.com

128 THE DEFENCE OF PNCthat PNC must be presupposed in all reasoning and rational thought; andit may especially be suggested by his aim in arguing (in IV. 4) that to denyPNC is to be committed to the view that thought and language areimpossible. But we must resist the impression that <strong>Aristotle</strong> defends PNConly or primarily as a logical principle. For he argues that PNC is ametaphysical principle, i.e. a principle about beings, and about beingssimply in so far as they are beings. He defends this view in IV. 3, when heargues that presuppositions of reasoning, such as PNC, are true of beingssimply in so far as beings are beings. But he defends this view moreradically in IV. 5–6, when he argues against those—phenomenalists andrelativists—who argue that PNC is true only of things as they appear to usand as we conceive them, and not true of the things themselves and ofthings without qualification. For he will argue (in IV. 5–6) that PNC isindeed true of the things themselves and of things without qualification; itis not only true of things as they appear to us and as we conceive them.<strong>Aristotle</strong>’s examination and defence of PNC occupies a pivotal positionin the Metaphysics. He argues, on the one hand, that PNC is a necessarycondition for the possibility of thought and language; but, on the otherhand, that PNC is true of the things themselves and of things withoutqualification, it is not only and not primarily true of things in so far as wecan think and speak of things. But it will emerge that the upshot of hisoverall argument is this: we must engage in metaphysics, i.e. in the projectof asking ‘What is being?’ and ‘What is primary being?’, and we mustsearch for an answer to these questions, if we at all want to consider howthought and language are possible. So, ultimately, the aim of theexamination of PNC is to provide vital motivation for engaging in his ownoverall project, i.e. metaphysics as he conceives it—indeed to show thatthis project is, in a way, inescapable.3Why PNC cannot itself be demonstratedIn IV. 3 <strong>Aristotle</strong> argues that PNC is the most ‘secure’ or ‘firm’ (bebaion) ofall claims, and that this is because its truth must be presupposed in allreasoning and rational thought. So PNC is a fundamental principle ofreasoning and rational thought; and this is why there is nothing more firmor secure than it. He concludes that because PNC is a fundamental principleof reasoning and rational thought, it cannot be demonstrated or proved tobe true; i.e. it cannot be deductively derived from something more firm orsecure. For its truth must be presupposed in all reasoning, and, inparticular, in all deductive reasoning.