Tuesday, November 27, 2012

Are logical laws true by convention?

From my C. S. Lewis's Dangerous Idea

“It is often supposed that the laws of logic are true by convention. But this is clearly not a coherent idea. Before conventions can be established, logic must already be supposed. If logical laws are human conventions, then presumably it is at least possible for us to have different conventions. But the laws of logic are conditions of intelligibility; without them we could not say anything. Part of what it means to say anything is to imply that the contradictory is false. Otherwise, language simply does not function in a declarative way. So the reality of logical laws cannot be denied without self-refutation, nor can their psychological relevance be denied without self-refutation” (82).


Dan Gillson said...

I have a few quibbles--yes, quibbles!--with this passage, but I'll just lay out one: not all speech-acts imply 'veracity' or 'falsity'. (In fact, I'd go so far to say that most of our utterances can't be understood in terms of 'true' or 'false'.) When I make some sort of a passionate utterance, I shouldn't be taken to imply that the opposite could be true; for instance, when I say "I love this beer!" I mean, to quote Wittgenstein, "this--is--so", i.e., I mean that "I love this beer!"

Daniel Anderson said...

Dan, Interesting point. I think Victor was getting at language in relation to conventions of logic in making arguments to demonstrate 'veracity' or 'falsity.' For example, you used structured argument to show that not all speech acts imply 'veracity' or 'falsity.'

Dan Gillson said...

That's a helpful gloss on this passage. I was taking Victor to mean that the laws of logical generally govern the conditions of speech and intelligibility.