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Does logic equal truth?

  1. May 1, 2003 #1
    i think logic is the logic for the limit of human intelligence
    like long time ago
    all people believe what aristotle said is very logic
    because that time it is the limit of human intelligence
    but now human is more clever than before
    so people now think aristotle is no logic
    what you think about logic??
  2. jcsd
  3. May 1, 2003 #2

    Ivan Seeking

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    We surely have more information which helps a lot.

    Many Greeks thought that all of reality could be deduced by pure logic. This approach obviously leads to errors. Also, one could argue that we are truly smarter now than then because of the world in which we live. The problem comes with how we define smart.

    Personally, the first time I read Socrates, and perhaps still, I was sure I had never encountered a smarter or cleverer individual. We just have to filter for the information disparity between our perspective and his.
  4. May 1, 2003 #3
    surely logic isn't dependant on intelligence? you say 'that's logical' not 'that's complicated and intelligently deduced using advanced theorems and knowledge of all that has come before'. logic is like 'gods are immortal, all men are mortal therefore no man is a god', that sort of thinking is even atributed to socrates, if something was 'logical' 2000 years ago it will remain so forever, the only thing that changes is what we use this logic to prove and with what axioms. if things were said back then that are now considered false then it is because the axioms were incorrect.
  5. May 1, 2003 #4
    maybe logic is come from this ideal
    but the problem is even at now we can't say what we learning is truth
    you said logic is immortal
    but theory of human create is not perfect
    so what u mean is no man is logic??
  6. May 1, 2003 #5
    In 1850 it was logical to assume the earth was flat. This is undoubtedly incorrect. Logic today tells us the earth is round. It was logical then to assume the opposite of our logic today. This tells us that logic is not universally or forever true, whereas, truth is universal and forever, so one would see that logic does not equal truth, nor would truth necessarily equal logic. More often than not truth is logical, but logical is not truth.

    EDIT: It seems that there are two kinds of logic, one based primarily on ignorance, or relative logic, and one based on universal laws/truths, or true logic, the former is much like a theory. You cannot distinuish between the two unless you either a) have all the facts or b) have an infinite amount of time to test them.
    Last edited: May 1, 2003
  7. May 1, 2003 #6

    i agree with that no man is perfect. but i believe there is no limit to human thinking. i have been thinking that if we want to proceed to higher level, we should go beyond logic and rational thinking. IMO.

    but ofcourse we should go through logical and rational thinking before we can go beyond. if you ask me what is beyond that... i still in the middle of searching.

    i think that logic is what we all use everyday for living. it just like common sense. we use logical thinking to explained everything that happen.
  8. May 1, 2003 #7


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    logic is truly subjective because it comes from the human mind...that doesn't mean that it is truthful or untruthful, but it depends entirely on the circumstances surrounding the claimed logic...
  9. May 1, 2003 #8
    Logic is the science of the absurd.

    As Kurt Godel demonstrated, any system requires certain axioms we must simply take on faith. In the case of logic, it is a faith in the absurd. In fact, all the various kinds of logistics that have been developed over the eons are ultimately based on reductio ad absurdum, a systematic way of demonstrating that alternative ways of thinking are at least as absurd as the logic we are using.

    Because of this logic can be seen as a systematic means of organizing absurdities into heirarchies. A tautological way of thinking which only has meaning within the context of human perception and specific applications. Before the discovery that the world is round, for example, to think the world was round was considered absurd and illogical. Before Galileo demonstrated the weak equivalency principle, it was considered absurd and illogical to believe objects of different weights could fall to earth at the same rate.

    Thus, to say logic is the limit of human perception is to deny the absurd foundations of logic. To deny our own irrational feelings among other things. :0)
  10. May 1, 2003 #9

    Les Sleeth

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    Logic is not open to subjective interpretation, but rather is as close to mathematical reasoning as one can get. In intelligence, and that is reason, there are really two parts: logic and premises. As Ivan said, it used to be believed that one could arrive at truth by logic alone, and this rationalistic view dominated philosophy until the 19th century when empiricism really took off.

    Then it was clearly recognized that the information one reasons with must be accurate for logic to lead one to accurate conclusions. Thus experience was solidly incorporated into the reasoning process. Premises began to require the experience of observation to validate them. That combined with the systematizing of logic with works like Boole’s Mathematical Analysis of Logic resulted in great discoveries in logic that came to be used by linguists, scientists, philosophers, mathematicians, electronic engineers and even music composers and psychologists.

    There still remains some question about what sorts of experience should be permitted to establish premises. People have argued that intuition and inner experience have relevance, others say only sense experience is to be allowed. But I have to disagree with Wuli that the foundations of logic are absurd. The methods of logic are virtually undisputed and function flawlessly when applied correctly . . . it is the reason of order, and it is used to help understand that which has order. What may be absurd is when people assume order (and therefore logic) is all there is to existence; but that would be due to the absurdity of the premise, and not a fault of logic.
  11. May 1, 2003 #10
    Logic is also subjective because there are different reasoning systems that can be used within the realm of "logic". One could make an utterly preposterous conclusion, from sound/reasonable premises - but the fact that s/he is using premises to build toward a conclusion means that s/he is using logic.
  12. May 1, 2003 #11

    Les Sleeth

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    If you want to say that people make up their own rules, and ignore the extremely well-established discipline of logic, then I suppose you can say it can be subjective . . . but that's not really logic either.

    If people obey the formal rules of logic, and reason with a correct and complete set of premises, then the conclusion will be correct every time. When an incorrect conclusion is found to have resulted from correct logic, it is always because of discovering something was missing from the premises. So proper logic is not subjective.
  13. May 1, 2003 #12
    Without the concept of the absurd to provide context, logic has no meaning. Without the illogical, the logical has no meaning. Hence you contradict yourself when you say, "what may be absurd is when people assume order is all there is to existence."

    The highly structured language of logic is built upon a foundation of natural language which is repleate with vague terms such as "absurd". Chaos and order, vague and explicite, define each other and, as history has repeatedly demonstrated, what we have believed to be explicitely ordered has turned out to be random and vague and vice versa. It may be expedient and practical in many respects to assume some things are ultimately ordered, but in the final analysis the map is not the territory by the very definition of logic. To assert otherwise is to invoke absurdity.
  14. May 1, 2003 #13
    u all think logic is not equal to truth....right??
  15. May 1, 2003 #14
    This is incorrect. If I make the premises:

    1) Everything we know about reality is known through our senses.

    2) We can never experience anything, outside of our own conscious awareness.

    And then conclude that reality must come from within. I have come to Lifegazer's Mind hypothesis with perfectly reasonable/true premises. That doesn't mean that lifegazer is necessarily right, does it?
  16. May 1, 2003 #15

    Les Sleeth

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    I suspect your views on paradox make you want to create one in every setting. It may be that being able to recognize illogic is a skill one needs to effectively apply logic, but I don't believe it has much to do with providing the context. Order exists, and we had nothing to do with that. It is here, and it overwhelmingly influences our existence. The rules that link order can be represented in the mind, and the mental linkage between order principles is logic. If everyone were always perfectly logical, then there would be no need to know about illogic. Therefore, logic can stand on its own because it reflects a certain way reality actually works.

    Does reality operate chaotically too? Yes, but logic isn't about that. Logic is about what it's about, and in that respect it seems to work perfectly.

    What "we have believed" to be ordered has nothing to do with logic. If it really is ordered, then logic can be used with it. Whether or not things are ultimately ordered also is irrelevant. All that matters is that some aspects of reality are ordered, and logic is the mental tool we have for understanding it. Because order has principles, so too does logic. They are not absurd, and they are not subjective (except in the sense they are applied inside one's brain); logic principles simply mirror something that goes on in reality. And it is pointless to object they can't work perfectly on everything. They aren't meant for everthing.
  17. May 1, 2003 #16
    There are multiple kinds of logic just as there are multiple kinds of mathematics. Some mathematics say 1+1=5. No, logic is not equal to truth, at least, not outside of a given context. At best logic is a pragmatic pratice and at worste a form of fundamentalism which can lead to all sorts of destructive behavior.
  18. May 1, 2003 #17
  19. May 1, 2003 #18
    logic = truth: when logic is logical.
  20. May 1, 2003 #19

    Les Sleeth

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    Yes, but are his premises correct? (Plus, even if they are I don't see how his conclusion follows.) See, if you want to take philosophy back to the dark ages, then you can assert anything as a premise and then go on a reasoning lark. But today we accept the principle of the empirical method for establishing a premise, and that is it must be verified by experience.

    How do you verify "We can never experience anything, outside of our own conscious awareness"? It is true we can only experience our own consciousness, but all appearances tell us we are being fed information from outside ourselves. How can LG prove his premise experientially? And it is one thing to say we can only know reality within, and another to say all of reality itself is within. It doesn't distinguish between the knower and what is known. Again, that contradicts our experience.
  21. May 1, 2003 #20
    how you defined which logic is logical??
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