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1/25/06 6:26 PM
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Logic Rules
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Edited: 25-Jan-06
Member Since: 08/01/2005
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Can you analyze this for me: "Logic cannot prove either existence or non-existence because you use existence as a given when you use logic at all." I'm stumped.
1/26/06 2:38 AM
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Indrek R.
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Edited: 26-Jan-06
Member Since: 07/04/2002
Posts: 881
Hey Logic by itself cannot prove anything at all. Induction is always based on belief and deduction doesn´t give any new knowledge. Logic is just a tool :)
1/26/06 11:38 AM
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Edited: 26-Jan-06
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Logic by itself cannot prove anything at all. So it can't prove what's logical and what's illogical? I was debating a guy that claimed he wasn't an atheist or theist because "logic can't prove existence" or some weird shit. Logic is just a tool :) I don't know if that was a clever play on words, but tell me what exactly is it a tool for?
1/26/06 4:05 PM
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Indrek R.
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Edited: 26-Jan-06
Member Since: 07/04/2002
Posts: 886
You can show that something adheres to the rules of logic or that it is illogical or contradictory, but logic doesn´t give us any new knowledge. Nothing that wasn´t there in the premises. Deduction: Prem1: All x-s are mma fighters Prem2: John is x Conclusion: John is a mma fighter This is a logical conclusion, but as you can see there is no "new" information in the conclusion. Everything is there in the premises. Most of the knowledge is based on induction, but induction in a way is based on belief. Inductive sentences give us new knowledge of reality and deductive do not. Logic as a tool can help you construct arguments or make stuff hidden in premises explicit, but doesn´t give us new knowledge. You cannot say anything about reality with logic only. Or so I argue and many have argued.
1/26/06 4:12 PM
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Edited: 26-Jan-06
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do you know any good books on the topic of logic?
1/27/06 10:55 AM
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Indrek R.
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Edited: 27-Jan-06
Member Since: 07/04/2002
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Logic per se isn´t really my thing. I am more into ethics . I just know what i know about the courses from the uni about Logics, Physics and philosophy etc. Do a book search on logic on amazon and read the reviews - I can bet you´ll find some good stuff.
1/28/06 5:36 AM
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FudoMyoo
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Edited: 28-Jan-06 05:38 AM
Member Since: 01/01/2001
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"Logic cannot prove either existence or non-existence"

I think what he meant is that Logic is analytical and apriori. You don´t need to rely on experience/empirics to know that the syllogism about MMA-fighters Indrek created is correct. Just like the truth 2+5=7 is also independent of any empirical observation. questions about existence are metaphysical and if you are a naturalist; empirical.

"Logic by itself cannot prove anything at all."

Well, it can. Just like you yourself showed above, Logic can show if a n argument is deductevily valid. It´s all about proving. But I agree that there is really no new information in a logical conclusion that didn´t already exist in the premises. Some argue that Logic is only about form, and formal validity, but I disagree with that.

"do you know any good books on the topic of logic? "

Yes, I can really recommend Lepores Meaning and Argument: An Introduction to Logic Through Language

http://www.amazon.com/gp/product/1405107839/qid=1138444274/sr=1-1/ref=sr_1_1/104-6359089-5359154?s=books&v=glance&n=283155

It´s really good for anyone that hasn´t studied Logic before, it goes through everything in the most basic and pedagogic way, but still it contains alot of knowledge, from propositional logic to predicate logic with identy and relations. I have read quite some books on logic now, and this one is by far the best one I´ve read.

1/29/06 4:04 AM
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Indrek R.
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Edited: 29-Jan-06
Member Since: 07/04/2002
Posts: 892
Well I can only agree with FudoMyoo :)

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