Aristotle on Metaphysics(2004) - Bibotu.com

138 THE DEFENCE OF PNCPNC is a transcendental principle, i.e. a principle that is primarily aboutthought and language about things and only as a consequence aboutthings. Indeed, it will emerge that <strong>Aristotle</strong> thinks that the relation is thereverse, i.e. PNC is primarily about things and only as a consequenceabout thought and language about things. This accords with the analogy:it is because grass is green that it can visually appear green to creatures withcertain cognitive capacities; it is not because grass can visually appear greento creatures with certain cognitive capacities that it is green. In general, itwill emerge that <strong>Aristotle</strong> thinks that what explains why it is possible tothink and speak about things is the nature of the things themselves (seeChapter 6).6How can one deny PNC?<strong>Aristotle</strong> argues that PNC is true, and that it is impossible to deny it. It isimpossible to deny it in the sense that it is impossible to accept theconsequences of denying it. But he also thinks that there are thinkers whodeny PNC. So he thinks that those who deny PNC do not recognize whatthe consequences are of denying it, or they do not recognize why it isimpossible to accept these consequences. He does not find it at allsurprising that some thinkers deny PNC. For he does not think that it isobvious what the consequences are of denying PNC, or that they includeones that it is impossible to accept. However, he thinks that it is possible toshow what the consequences are of denying PNC, and this is what he setsout to do in the defence of PNC. The overall conclusion of the defence isthat if PNC were not true of things, then it would be impossible to usethoughts or words to signify things, so it would be impossible to think orspeak about things.<strong>Aristotle</strong> thinks that different thinkers have wanted to deny PNC, suchas Heracleitus (1005 b 25), Protagoras (1007 b 21), and some of the ‘naturalphilosophers’ (hoi peri phuseōs, 1006 a 2). But he also thinks that some ofthose who argue against PNC do so fallaciously; i.e. they assert somethingwhich they think implies the falsity of PNC, but which does not reallyhave this implication. For example (see 1009 a 22–38), some naturalphilosophers, such as Anaxagoras and Democritus, argue that in order tounderstand the nature of change, we need to suppose that something canat the same time be in opposite states (e.g. both green and red), whichimplies the denial of PNC. But <strong>Aristotle</strong> responds that it is possible tounderstand the nature of change without denying PNC, and he tries toexplain how this is possible.