Logic vs evidence

Discussion in 'General Philosophy' started by Magical Realist, Mar 30, 2016.

  1. Russ_Watters Not a Trump supporter... Valued Senior Member

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    You are contradicting yourself for no good reason. The last sentence means that Newton's laws are outdated logic (produce wrong results) for most of the cases for which they were originally used, including the example you gave.

    I can't fathom why you keep doing this to yourself. You actually started a decent discussion -- why are you trying to derail it?
     
    Last edited: Apr 1, 2016
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  3. Magical Realist Valued Senior Member

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    No..Newton's laws apply to the everyday objects of our world traveling much less than the speed of light within inertial frames of reference. That is the vast majority of cases in our world. Not outdated in any sense.
     
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  5. Daecon Kiwi fruit Valued Senior Member

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    So... the complete opposite of the quantum realm, then?
     
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  7. exchemist Valued Senior Member

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    Hmm. I wonder if there is a linguistic difference here between N America and Europe. I see you and other contributors speaking of "logic" when you seem to mean what I would call a theory or system of theories. Dave for example speaks of outdated logic, referring to Newtonian physics. But to me, "logic" is a process of thought, not any particular theory or set of assumptions for modelling the world. That is why I keep maintaining it is the assumptions, the postulates, on which theories are built, that change, rather than logic itself. But enough - I think we both know what we mean.
     
    Last edited: Apr 1, 2016
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  8. exchemist Valued Senior Member

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    I agree. In science we use various different models to suit the task at hand. None of them is perfect and many involve various degrees of simplification or approximation, so that we can get adequately good results with minimum effort. I do not consider Newtonian physics to be "outdated", just because it has been shown to be an approximation. It remains good enough for most of us, most of the time, and is used a lot more widely than the more rigorous approaches of GR or QM. One simply needs to be aware of its limitations. The same can be said for many theories in science.
     
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  9. Baldeee Valued Senior Member

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    So you're accepting that it doesn't defy logic per se, as was originally claimed by MR?

    As exchemist suggests, perhaps there is a difference in what we mean by "logic".
    To me it is simply a case not of it "defying logic" but of recognising that there are different forms of logic and that not all may be appropriate to the matter in hand.
    But I would contend that if something exists then it does not defy logic.
    If it can be modelled then it does not defy logic (the model must work on some underlying logic).
     
  10. Baldeee Valued Senior Member

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    If you clearly stated it then people wouldn't be struggling to comprehend it, would they.
    What you said may well be relevant, but unless one can comprehend what you said it could simply be a pile of manure.
    It probably isn't, though, but I am struggling to understand your reluctance to provide that clarity.

    The inability to understand French, for example, does not make someone unintelligent.
    The ability to write a post that some have difficulty in comprehending does also not make one intelligent.
     
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  11. exchemist Valued Senior Member

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    Returning to the "parsimony" point, which I left dangling, the "principle of parsimony" is just a synonym for the slightly overworked Ockham*'s Razor, a.k.a. lex parsimoniae. I am arguing that we are being quite reasonable to use a theory that is as simple as possible up to the point where it is shown not to work. We only add to, or replace, it once we have to due to new observations that we cannot account for. The process of discovering that point of inadequacy inevitably must involve pushing the theory into an area in which it is found to fail. (And, at least in my European terminology, it is the theory we push, rather than logic. In this parlance, logic is, or should be, with us at every step and is never invalidated.)

    * I prefer this spelling, as it is how we spell the village in Surrey where he is said to have been born. Im not sure where the "Occam" spelling came from.
     
  12. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Again: yes, they can be used, even though they produce wrong results. They produce wrong results because they are outdated.
     
  13. PhysBang Valued Senior Member

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    That's simply not the case.

    The relativistic correction to Newtonian Mechanics for Mercury's orbit is 43/60 or a degree every 100 years. Newtonian Mechanics is crazy accurate on a great deal of scales. Many astronomers simply do not learn GR in any detail because they will never use it.
     
  14. exchemist Valued Senior Member

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    Russ, I do find you rather fundamentalist on this issue. Maybe it is the difference between a physicist and a chemist, I don't know, but I do think that saying Newtonian physics is "wrong" is a bit misleading. As Physbang says, it is accurate enough for almost all practical purposes. It remains the basis of almost all the technology used in modern society. It has been found to be only an approximation, yes, but one that is good enough for most of everyday human experience - and has the further merit that it is far, far easier to apply than the rigorous alternatives. If it were "wrong", we would not be able to build our bridges and cars using it.

    But my perspective may differ from yours, I do concede. We chemists use approximate methods all the time, as we have no choice: multi-electron atoms and multi-atom molecules are too complex to be treated any other way. I think we tend to see physical science as providing, not one "true" or "right" answer, but a toolkit of techniques and models, adapted for different purposes. Heresy?
     
  15. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Yes, sometimes the word "logic" alone is referring to a specific line of logic: a specific theory.

    I don't think it is a hairsplit, though, to say that sometimes what people think is a fact is really a conclusion or assumption. And that if you change the premise, the logic that follows it must also change.
     
  16. exchemist Valued Senior Member

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    That I certainly agree with. The moment you move beyond the observation to the inferences you draw from it, you start to lose some degree of certainty, however small, because you start to bring in other assumptions.
     
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  17. Russ_Watters Not a Trump supporter... Valued Senior Member

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    All of that is fine except that I'm an engineer, not a physicist.

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    In this case, the difference between "right" and "wrong" answers is a matter of how tight the error bars are. Since I'm an engineer, my error bars tend to be very wide and a lot of the skill/art of engineering is managing simplifying assumptions and sources of error. I see my calculations as being always wrong, but close enough.
     
  18. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    Sure, when someone says "what's the logic behind that?" they refer to the line of thought, but when someone says that it "defies logic" then this is surely a more encompassing usage than a single line or a specific theory? It seems to be a claim that it is beyond comprehension, beyond formulation within arguments, theories, thoughts etc.
    At last that was how I read it, and I assume exchemist understood it that way as well.
    But thanks for the clarification.
    Only "sometimes"?

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    Using the term as you have explained, then there is no disagreement, but if one has, say, used deductive logic to get from the premise to the conclusion, they can still use that same type of logic to get to a new conclusion given the new premise. I.e. The logic, in this understanding of the term, need not change.

    Hence QE may well defy certain types of logic (Aristotelian, for example, which as MR pointed out uses the law of identity), but not logic all together.
     
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  19. exchemist Valued Senior Member

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    Well exactly. I mean, we all know GR is more accurate than Newton but it's a bastard to use, so you only choose it when you have to. Same with QM. And even with QM there are a lot of shortcuts that chemists use, for example relying on symmetry to get qualitative answers and correct concepts, rather than numerical calculation.

    I would contend that all such approximate theories are "right", or "right enough", so long as the user is aware of the limitations and how these theories relate to the full picture, so that they do not use them inappropriately.
     
  20. Russ_Watters Not a Trump supporter... Valued Senior Member

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    I don't think I'd ever use the term in that way in such a discussion. Similarly, if I say "the math has to change", I'm not referring to the rules of math (1+1=2 has not changed), I'm referring to the results of a mathematical exercise.

    The rules of logic are what they are and are not what this is about.
     
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  21. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Sure: "Right enough" is just a nicer way of saying "not too wrong".
     
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  22. Russ_Watters Not a Trump supporter... Valued Senior Member

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    It is worth remembering where the entry point to this conversation was:
    MR's retort brought up billiards, but he's just being himself. Clearly, we all agree that Newtonian theories are "right enough" or "not too wrong" for billiards. But I'm sure we also agree that Dave was totally correct that in the domain of QM, Newtonian physics is very, very wrong.
     
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  23. exchemist Valued Senior Member

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    Well, Newtonian physics doesn't even try to address things like the structure of the atom, so I think I'd give Newton a break here - except that his implicitly deterministic philosophy was itself shown to be flawed. If you say "classical physics", including Maxwell's theory of EM radiation, Rayleigh's harmonic oscillator approach to the black body etc, then yes, that on its own leads to famously wrong answers. But I still think I'd say classical physics breaks down in this domain, rather than use the term "wrong": it just seems too dismissive. But it's probably just my personal approach to science. My 6th form chemistry teacher casts a long -and benign- shadow over my intellectual life.

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    Last edited: Apr 1, 2016

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