metrictensor said:
You words may have contradicted what I said but if you look deeper you will see that you agreed with my main point. I said they are contingently true (which you disagree with) and can be so in only two ways (1) conformity to reality (2) conformity to a set of rules. In either case the truths are contingently true. Since you said that "truth is determined by the rules of the system" you implicitly agree with my categorization and therefore the contingent nature of mathematical truths.
Okay, I can better explain what I meant. (Classical) Propositional logic is simple and the system I know the most about, so I'll stick with it. A valuation on formal language L is a function from the set of formulas of L to a set of two distinct objects. A formula f is contingent iff there exist valuations V and W such that the value that V assigns to f does not equal the value that W assigns to f. That's what I meant by 'contingent'. How else do you evaluate a formula (mathematical statement)? Is there even any reason to interpret x as true and y as false (or x as false and y as true)?
Since most people usually use true and false instead of x and y, by truth being determined by the rules, I just meant part of the system is a valuation. The valuation is not reality; It's an abstract object. I guess you could try to define the valuations to conform to reality, but I don't know how you would get around the subjective nature of experience.
If the best you can do is refer me to authority then we have no room left to talk.
You're talking about things that have already been precisely defined. If you're confused about the definitions, what else can you do but look them up? Are you talking about math or about your own original ideas?
The only correct thing you have said so far was a repetition of what I already wrote.
"Tautologies and contradictions are non-contingent statements," is true by definition.
The rules of the game. As you put it "truth is determined by the rules of the system". If I land on a space that have a shoot I must go down. This is a truth of the game. If I land on that space and move up I have contradicted the rules and it is false.
Why do the inference rules have truth-values? Wouldn't the formulas of the game be things like "Player p is on space x at turn t" or "Player p lands on space x implies player p moves to space y"? Also, how do you work out the valuation?
V(f) = {x iff everyone playing the game agrees that f is true, y otherwise}
V(f) = {x iff every player observes f, y otherwise}
? The truth of "Player p lands on space x implies player p moves to space y" would then depend on whether the players actually followed the rules of the game, if and what they agree they observed, or, worse, people having access to each other's conscious experience. That's probably why mathematicians define valuations instead of letting them depend on reality.
Where I come from we provide reasons for our statements. If the best you can do is say "because that is how it is" you need to go to the kindergarden message board. In addition, I have two university degrees in physics and math so I don't think you need to teach me about math but maybe I could teach you shoots and ladders since its a little kid's game.
I have some advice too: Read PF's rules. Insults aren't allowed. Luckily for me, the number of degrees you've earned doesn't determine the truth of your arguments. You didn't learn about logical fallacies in your math classes?
You haven't made a contestable statement here. Think about walking. We can all conceive of walking and as long as we don't bump into something we keep going. This is an understanding of infinity. What I was saying re: the flying pink elephant is that all our concepts come from experience with the empirical world. There is no human nature or innate human abilities that are simply there as a result of being born. There is only experience and habit.
How do babies learn how to breath? They inhale fluid in the womb. They do many other things in the womb before they even begin to store memories. How do they learn to do those things? What have you read about child development that makes you think humans have no innate abilities?
Besides, I never said people were born with a knowledge of math. In fact, I said, "most humans happen to be born with working senses but not a working knowledge of math."
I don't really care about your opinions. Make contestable statements. I have made several assertions that you have not refuted. That is I make a claim and you need to find an example that contradics my position.
If you don't care about my opinions, then you don't need to read them. I don't have to refute all of your assertions, and I wasn't trying to. If you explained your position as much as you changed the subject and insulted people, it would be easier to understand what exactly your position is. You're the one making claims that you haven't supported.
Opinions are contestable statements, so what are you talking about?
You may not have seen something I added:
Also, are you suggesting you know of an a posteriori proof that two parallel straight lines -lines are infinitely long- never intersect? Maybe I've misunderstood- a posteriori proof is just experience, right? How do you observe a one-dimensional object? And an infinite length of space? And make sure it is actually percfectly straight?