Posted by alexandra_k on December 2, 2005, at 22:10:28 [reposted on December 3, 2005, at 14:38:52 | original URL]
In reply to Re: ...addendum, posted by linkadge on December 2, 2005, at 16:34:14
> You are right, that statements are either true or false.
in a two-valued logic your statement is true
this is the principle of bivalenceEITHER T OR F AND NOT BOTH
> But if you have a statement that has not been proven true or false, then it cannot be deemed true or false.we do not know whether tomorrow will be the end of the world or not. the statement 'the world will end at time t' is either true or false independently of what (if anything) we can know about it...
we might not know whether a certain mathematical theorum is true or false, but it is either true or false independently of whether we ever manage to figure that out or not...> There could be a third yet undescoverfed relation factor.
many valued logics reject the principle of bivalence: that every proposition is either true or false and not both. there are two forms of rejection: the first is the idea that there are more values than these. the second is that propositions may be neither true nor false (lacking a truth value).
This manouver is to deal with some special kinds of statements such as
'the present king of france is bald'.
It is not T, so it must be F.
but to say it is F is to imply / logically entail that
'there is a present king of france and that present king of france is bald' is T.
but of course 'there is a present king of france' is F. and thus 'there is a present king of france and that king of france is bald' is F.there are contradictions in two-valued logic (which is a disgrace)
> Say, if we knew that, due to Ace's popularity, there was a statistic likelyhood that others would believe the same.
(P1) Ace is a popular person
(P2) Most babblers believe what a popular person believes
(P3) Ace is a babbler and Ace believes 'I am smarter than my p-doc'
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(C) Most (the same referent as P3) babblers believe 'I am smarter than my p-docThat argument is deductively valid.
(It is impossible to describe a situation where the premises are true and the conclusion false without contradiction)The relationship between the premises and conclusion is very tight
The trouble is that if people believe premiss 1 or 2 (or both) to be false then they have no reason to believe the conclusion on the basis of the argument.
(Regardless of whether the conclusion is true or not people have no reason to believe the conclusion on the basis of the argument and thus the argument is not rationally persuasive)
In order for a valid argument to be rationally persuasive
Other people would have to be likely to accept the truth of the premises
If you have a valid argument and people believe the premisses are all true then they would be endorsing contradiction to deny the conclusion
> If this were true, then the statement would be true.The argument would be deductively valid / its degree of inductive force would be 100%
But...
If we think either premiss 1 or 2 (or both) are false then we have no reason to come to believe the conclusion.
> So simple if, then statements cannot be discounted based on the fact that a connection cannot be seen.P1) grass is green
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C) the sun is hotThere is no contradiction in imagining a possible world with green grass and no sun or a cold sun or whatever. The argument is not deductively valid. The argument is not rationally persuasive (because it is an attempt at a deductive argument and it is invalid).
Yet...
The sun is hot.
We just don't have reason to believe the truth of the conclusion
ON THE BASIS OF
The reason (premiss) provided.
poster:alexandra_k
thread:585017
URL: http://www.dr-bob.org/babble/social/20051203/msgs/585045.html