Logic vs evidence

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

  1. Magical Realist Valued Senior Member

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    Which would you rather accept as true: something that was logical but for which there was no evidence? Or something for which there was evidence but which defied logic? Are there instances of logic and evidence conflicting in our experience? Examples?
     
    Last edited: Mar 30, 2016
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  3. Daecon Kiwi fruit Valued Senior Member

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    That would depend entirely on how good the evidence is, as you well know.
     
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  5. Magical Realist Valued Senior Member

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    So you're saying you'd accept evidence over logic?
     
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  7. wellwisher Banned Banned

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    Logic is only as good as the premises it is based on. While evidence, without proper context, can be misleading.

    For example, if we assume the earth is flat and finite, then if we sailed to the end of the ocean, where there is no land; boundary, there will be a huge waterfall. This logic is reasonable, but it is based on faulty premises. This line of logic can be disproven by sailing to the end of the ocean to see the hard evidence.

    On the other hand, if I take water and pour it into any container, it will fill the container to a certain point and then flatten out. This is evidence anyone can generate.The water in the container will not tip to one side, or form peaks but levels out.

    Since all the rivers flow into the ocean and we call that sea level, the earth have to be flat since water goes all around the earth. All I am doing is scaling up the original evidence. The original evidence breaks down at a certain level.

    In this cases, I may need to add some logic to better extrapolate the original evidence.

    In my opinion, it is best to start with evidence. This allows us to know which things are real and solid. These become your tool set of sound premises, which were know are not faulty. Logic is then used to connect the dots.
     
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  8. exchemist Valued Senior Member

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    There are none, so far as I am aware, because where there is evidence, it provides information that the logic has to take into account.

    If you think you have any examples, please provide them.
     
  9. Magical Realist Valued Senior Member

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    Quantum entanglement defies logic. Yet there is good evidence for it.
     
  10. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    How exactly does QE "defy logic"?
     
  11. Magical Realist Valued Senior Member

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    That one particle can instantaneously influence another one a million miles away isn't logical.

    "Entanglement is a sort of link between particles that correlates their properties even at vast distances; it defies the logic of classical physics yet is fundamental to quantum mechanics."==http://www.pbs.org/wgbh/nova/blogs/physics/2014/03/the-universe-made-me-do-it/

    In addition quantum theory itself seems to defy logic as well:

    "The reason why quantum mechanics holds a place apart from the rest of modern physics is that it is implausible. The physical behavior of extremely light-weight particles, like electrons and protons, defies Aristotelian logic. The logical problems of quantum mechanics are not even that deep. They run into trouble right at the beginning of Philosophy 101 with an apparently obvious tautology: an electron is either a particle, or it is not a particle. This sentence is clearly true. But in quantum mechanics I can also make the following true statement: an electron is a particle, and it is not a particle. This sentence is a contradiction in classical logic (violating the proposition {|-.~(p.~p)} in the notation of Russell and Whitehead), but it strikes at the fundamental core of quantum behavior. For indeed, an electron is a particle, and it is not a particle. It is a wave, and it is not a wave. It is found precisely where you observe it to be, yet it is nowhere before you observe it. You can know its momentum to infinite accuracy, yet only if it can be found anywhere in the universe. You can equally pin it down precisely inside an atom, yet its momentum can take almost any value at all.... Every statement seems to be either a contradiction, or a restriction. This is quantum mechanics! It is not the fact that quantum mechanics is unintuitive that gives it its allure, but that it lives in states that cannot logically exist."===https://www.physics.purdue.edu/nlo/Ch9.AgeOfEntanglement.pdf
     
    Last edited: Mar 30, 2016
  12. Beer w/Straw Transcendental Ignorance! Valued Senior Member

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    Logic in math is solid, and so are experiments in quantum mechanics.

    Can we say that common sense is logical, or, just ignorant?
     
  13. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    Again, how is this illogical?
    If you are saying that the conclusion does not follow from the given premises, but yet we observe the conclusion, then clearly the argument is unsound: and assuming the logic is valid then the premises themselves must be false.

    As your following quote states: "it defies the logic of classical physics..." I.e. the premises are unsound.
    This is therefore not saying that QE itself is logical, but that any argument trying to reach the conclusion of QE from classical physics can only do so with unsound logic.
    But that does not make QE itself illogical.

    Simply put: logic relates to an argument, not a thing.
    Something can only be considered illogical in relation to the premises you begin with.
     
  14. exchemist Valued Senior Member

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    My point exactly.

    If reproducible observation indicates something is the case, then logic will take that into account in drawing any conclusions.
     
  15. exchemist Valued Senior Member

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    No. See Sarkus's post, which makes the same point as I did.
     
  16. wellwisher Banned Banned

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    Quantum entanglements only defy logic and common sense, based on the premises of existing theory. If the premises of any theory are not proper, you will see anomalies that don't follow the theory. Existing theory, is the source of knowledge, used for common sense.

    For example, the layman may not be able to explain why an airplane flies based on things he observes in his own world. The theory behind his common sense does not include the principles of flight. This will appear to defy his common sense. On the other hand, if one is an aerodynamics specialist, one's basic understanding of lift, makes this anomaly appear as a common sense observation.

    The fact that existing theory can't explain quantum entanglements with common sense, shows the theory is weak or wrong. That existence of evidence, that defies common sense, means that it is time to go back to the drawing board, double check all the premises and maybe add some new ones. In the case of flight, the layman would need to study, so he can add new premises, so flight becomes part of his common sense.

    That has always been my approach. When exceptions appear and common sense breaks down, that means the theory has problems and can no longer support common sense. It is time for another option; premises and logic, that can makes this observation common sense.

    In physics, voids in common sense are seen as having nothing to do with weak theory. It is interpreted as meaning a random universe, since we all know the theory is perfect. Only the common riff raft can't see the emperor new clothes. Many people confuse prestige for sound theory. Prestige has no teeth, since it can't make the anomalies obey common sense. It is all bark, fighting the dying of the light, with subjectivity.

    When common sense breaks down, this should be a signal to all entrepreneurs the king has no clothes. Prestige can set up roads blocks to the advance of common sense, because advanced common sense can see the emperor is naked.
     
  17. Yazata Valued Senior Member

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    I don't think that logical form and evidence can be separated in the way you are trying to do.

    Being the conclusion of a logical argument is an extremely weak reason for believing in the truth of that conclusion.

    P1: If Magical Realist is sane, then Berlin is the capital of France.

    P2: Magical Realist is sane.

    C: Therefore Berlin is the capital of France.

    It's a valid inference and an entirely logical conclusion, despite neither of the premises being true.

    Logical validity is a function of the form of arguments. In order for logical arguments to have any persuasive force, they need to be sound as well as valid. And soundness is a function of the truth of the argument's premises as well as validity.

    If an argument leading to a particular conclusion was valid (as in my example above) but there was no evidence for the truth of its premises, then we wouldn't have any reason for agreeing with its conclusion.
     
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  18. Yazata Valued Senior Member

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    It might not be consistent with premises that things have to be in physical contact to influence each other or that influences can only propagate at the speed of light.

    I suspect that it might be a mistake to think of it as two particles influencing each other. Perhaps it's more along the lines of what we call two particles sharing a single property in common. Perhaps we aren't correctly imagining how particles and their properties are individuated.

    Maybe it's something other than a particle that sometimes displays particle-like characteristics and sometimes displays wave-like characteristics, despite not literally being either one.

    Something is either a man or not a man. So what should we make of Sherlock Holmes? He's a fictional character that takes the fictional form of a man. There's the Aristotelian law of the excluded middle, and there's also the informal fallacy of the excluded middle (false dichotomy). Keeping that straight requires some discussion.

    So why should laypeople like myself accept the truth of quantum mechanics? Because of all the pretty mathematical hieroglyphs? Mathematics is meaningless if we throw out logic. Because quantum mechanical conclusions are logically implied by the physical evidence? The difficulty there is obvious.

    In real life, there are many different logical systems.

    https://en.wikipedia.org/wiki/Non-classical_logic

    These might introduce new logical operators, like the modal operators in modal logic. Or they might reinterpret familiar logical concepts in unfamiliar ways.

    There have been attempts to invent a so-called 'quantum logic' to better model the relationships between observables and what-not in qm, though I believe that it's controversial whether such a move is necessary.

    My point being that none of this suggests that logic should be thrown out, only that some modifications or extensions of more classical forms of logic might arguably be necessary. But we already knew that modifications to traditional logic were necessary, from things like epistemic, many-valued and tense logics.
     
  19. Russ_Watters Not a Trump supporter... Valued Senior Member

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    In general, a factual premise forms a starting point for a logical argument and a final verification that the line of logic produced an accurate result. So I would typically say that evidence is king -- particularly since per your example, logic is often misunderstood/misapplied. That said, evidence quality can vary as well. But again, generally without *something* on which to base a line of logic, there is nowhere to start.
     
  20. exchemist Valued Senior Member

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    I'd have said, myself, that QM conclusions are indeed logically implied by the physical evidence. QM arose, surely, by the application of logic to the observations, did it not? One (logical) conclusion was that the terms "particle" and wave" could not be mutually exclusive at the atomic scale, or not in the simple way that had previously been assumed. Once the definition of terms changes, so may the logic that uses them.

    (By the way, I often think the classical term "particle", used so much in physics, is itself a highly artificial mental construction. We hardly ever seem to question that, because we are so familiar with it, but in fact it is a way of simplifying physical situations to the essence and stripping away side effects extraneous to the problem we wish to analyse. Treating objects as pointlike is pretty bizarre, when you think about it.)

    The fact that we still have some paradoxes in QM should I think be taken to indicate that there may be more to learn about the world, i.e. the theory may be incomplete in some way, than that QM defies logic. If it really did "defy logic" nobody would accept it. I see MR was in fact quoting from a book by a Physics prof (D. Nolte) at Purdue. I suspect that Nolte was probably using hyperbole to stimulate interest in his readers, since this is evidently a book aimed at a popular audience rather than at specialists.
     
  21. Magical Realist Valued Senior Member

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    But science is always defying common sense. Common sense realism says the car is blue. That the property of blueness inheres in the paint on the car. But brain studies show blueness is a sensation created entirely in the brain. Common sense says time is absolute. But Einstein has shown that it is relative to motion. This all defies common sense. Common sense also tells us a thing can't be in two contradictory states at the same time. But Schrodinger's cat is in what is called a superposition: it is dead and alive at the same time. We go by what science has empirically proven to be true, not by our assumptions formed based on some culturally disseminated "common sense"..
     
  22. Magical Realist Valued Senior Member

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    I still contend that quantum theory defies Aristotlean logic, particularly the law of identity:

    A is A: Aristotle's Law of Identity
    "Everything that exists has a specific nature. Each entity exists as something in particular and it has characteristics that are a part of what it is. "This leaf is red, solid, dry, rough, and flammable." "This book is white, and has 312 pages." "This coin is round, dense, smooth, and has a picture on it." In all three of these cases we are referring to an entity with a specific identity; the particular type of identity, or the trait discussed, is not important. Their identities include all of their features, not just those mentioned.

    Identity is the concept that refers to this aspect of existence; the aspect of existing as something in particular, with specific characteristics. An entity without an identity cannot exist because it would be nothing. To exist is to exist as something, and that means to exist with a particular identity.

    To have an identity means to have a single identity; an object cannot have two identities. A tree cannot be a telephone, and a dog cannot be a cat. Each entity exists as something specific, its identity is particular, and it cannot exist as something else. An entity can have more than one characteristic, but any characteristic it has is a part of its identity. A car can be both blue and red, but not at the same time or not in the same respect. Whatever portion is blue cannot be red at the same time, in the same way. Half the car can be red, and the other half blue. But the whole car can't be both red and blue. These two traits, blue and red, each have single, particular identities.

    The concept of identity is important because it makes explicit that reality has a definite nature. Since reality has an identity, it is knowable. Since it exists in a particular way, it has no contradictions."===http://www.importanceofphilosophy.com/Metaphysics_Identity.html
     
  23. krash661 [MK6] transitioning scifi to reality Valued Senior Member

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    Simply-- what nature shows..(shakes head)-- except of the fact that human technology and progression within this stage of humanity, is a massive hampering of the advancement of humanity in these elements. humanity/humans needs to keep in mind that they are, simply, a newborn element of existence. to be honest-- the majority of humanity does not have any sort of understanding, knowledge, and wisdom of the meaning, definition,and process of logic.
     

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