Logic vs evidence

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

  1. Yazata Valued Senior Member

    'Logic' means the same thing in Europe and North America, as far as I'm aware. I think that a number of people in this thread are misusing the word 'logic'.

    I'd say that logic is the study of logical consequence, such that if a set of propositions P1, P2, P3 ... Pn logically imply a conclusion C, then if P1, P2, P3 ... Pn are all true, then C must be true as well. (It's important to note that this implicative relation can hold even if some of the P premises aren't in fact true, provided only that if all the Ps were true, the conclusion C would have to be true too.)

    I agree with that 100%. When we change physical theories we aren't typically changing the underlying principles of reasoning itself, the principles of logical consequence and implication that are embodied in mathematical as well as verbal reasoning. We are just adopting different premises that imply different conclusions.
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  3. exchemist Valued Senior Member

    Thanks Yazata, I was maybe trying to be diplomatic, for once. It is my impression that the arguably somewhat loose usage of "logic" may occur mainly in expressions that are more common across the water than they are here. But I think it is all clarified now - except perhaps for Sarkus's and MR's point (Prof Nolte's originally, in MR's quote) about Aristotelian identity vis-a-vis quantum wave/particle duality. They say QM defies this logic. I'm not sure about that, as I think it is again to do with altering our model, to avoid claiming that an entity is one or the other. But I'm not a logician.
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  5. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

    Just a point of note: my view is that if QM doesn't satisfy the law of identity (I actually don't know if it does or not) then surely by default it defies classic Aristotelian logic (which is based on that law, among others).
    But I'm not certain that QM does violate the law of identity - I was more thinking that it's the superposition that would suggest it does, not wave/particle duality - but even if it does there are other forms of logic that can cope with the issue - e.g. quantum logic, as Yazata (?) mentioned previously.
    So I think we agree... ?
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  7. Yazata Valued Senior Member

    Thanks for clarifying that. I think that your interpretation might be closer to MR's original intent in his O.P. than my reading was.

    Here's what he asked:

    "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?"

    Was he asking us whether we would rather embrace the implications of currently popular scientific theory over accepting the truth or probability of anomalous evidence that seemingly contradicts what that theory predicts? (With the underlying principles of logical reasoning remaining constant throughout.)

    Read that way, I'm not sure what my answer would be. I think a great deal would depend on how well substantiated the theory appeared to me to be. Newtonian physics has been substantiated in countless ways for centuries. So gross (as opposed to subtle) violations of Newtonian mechanics would seem inherently unlikely to me. So if somebody reports something inconsistent with Newtonian physics, I'd be inclined to not believe it. As engineers everywhere have verified over and over, forces, masses and accelerations behave as Newton and his successors predicted. It's why airplanes don't fall out of the sky and why your car engine works.

    But string-theory or cosmic inflation seem a lot more speculative to me. I would probably be willing to entertain a violation of these theories' predictions without a lot of kicking and screaming.

    And having said that, I do think that just about any reported anomaly has a non-zero positive likelihood of being true. I'm very reluctant to assign the 'impossible' label to anything. And no theory has a probability of 1, absolute certainty, no matter how well-confirmed it might be. We saw that with Newtonian physics, which proved to be inaccurate on both the micro-scale and at high relative velocities.
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  8. C C Consular Corps - "the backbone of diplomacy" Valued Senior Member

    If going by Smolin's account (below) of most physicists being lackadaisical about global coherence (i.e., lacking Albert's relentless devotion to it), then even in physics there is apparently no pre-conditional commitment to all observations, events, or "things" having to hang together properly. [Though of course free-lance individuals or teams of theorists / researchers have to be concerned about the internal consistency of their own narrow area of focus / work, or local-oriented projects.] Which is to say, IF there is any demand that reality in bulk must reliably conform to either the basics of logic or to a particular scheme of reason, it would seem to fall out of the tenets of assorted "-isms" (naturalism, materialism / physicalism, etc).

    So before proceeding, that might have to be sorted out: Identifying the source or authority for a prescription that the world or whatever must absolutely hang together properly. Even should its provenance just be some kind informal "instinct" that members of professional institutions are appealing to as valid.

    Lee Smolin: . . . Physicists I’ve met who knew Einstein told me they found his thinking slow compared with the stars of the day. While he was competent enough with the basic mathematical tools of physics, many other physicists surrounding him in Berlin and Princeton were better at it. So what accounted for his genius? In retrospect, I believe what allowed Einstein to achieve so much was primarily a moral quality. He simply cared far more than most of his colleagues that the laws of physics should explain everything in nature coherently and consistently. As a result, he was acutely sensitive to flaws and contradictions in the logical structure of physical theories.

    Einstein’s ability to see flaws and his fierce refusal to compromise had real repercussions. His professors did not support him in his search for an academic job, and he was unemployed until he found work as a patent inspector in Bern, Switzerland. The problem was not just that he skipped classes. He saw right through his elders’ complacent acceptance of Newtonian physics. The young Einstein was obsessed with logical flaws that were glaringly obvious, but only to him. While the great English physicist Lord Rayleigh said he saw “only a few clouds on the horizon” remaining to be understood, the 16-year-old Einstein wondered what would happen to his image in a mirror if he traveled at the speed of light.

    From the outset, Einstein’s single goal in science was to discover what he called theories of principle. These postulate general rules that all phenomena must satisfy. If such theories are true, they must apply universally. [...] Einstein’s whole life was a search for a theory of principles. It is hard to imagine he would have sustained interest in a theory for which, after more than 30 years of intensive investigation, no one is able to put forward any core principles. [...] I think a sober assessment is that up till now, almost all of us who work in theoretical physics have failed to live up to Einstein’s legacy. His demand for a coherent theory of principle was uncompromising. It has not been reached—not by quantum theory, not by special or general relativity, not by anything invented since. Einstein’s moral clarity, his insistence that we should accept nothing less than a theory that gives a completely coherent account of individual phenomena, cannot be followed unless we reject almost all contemporary theoretical physics as insufficient.

    So is it possible to follow the path of Einstein? To do so, you cannot be a crank; you must be a well-trained physicist, literate in current theories and aware of their limitations. And you must insist on absolute clarity in your own work, rather than follow any fad or popular direction. Given the pressures of competition for academic positions, to follow Einstein’s path is to risk the price that he paid: unemployment in spite of abundant talent and skill at the craft of theoretical physics.

    In my whole career as a theoretical physicist, I have known only a handful of colleagues who truly can be said to follow Einstein’s path. They are driven, as Einstein was, by a moral need for clear understanding. In everything they do, these few strive continually to invent a new theory of principle that could satisfy the strictest demands of coherence and consistency, without regard to fashion or the professional consequences. Most have paid for their independence, in a harder career path than equally talented scientists who follow the research agendas of the big professors. Let us be frank and admit that most of us have neither the courage nor the patience to emulate Einstein....
    --Einstein's Lonely Path; Discover Magazine, Sept 2004 issue

    - - - - - - -

    Some specific QM & relativity bits, excluded from the synoptic theme above:

    . . . There are by now only a small minority of physicists who think Einstein was right to reject quantum theory as the foundation of our scientific description of nature. [...] Einstein was willing to concede that quantum mechanics explains the recorded behavior of the subatomic world, but he was convinced it had two flaws.

    [...] Quantum mechanics was not the only theory that bothered Einstein. Few people have appreciated how dissatisfied he was with his own theories of relativity. [...] Why? The main reason was that he wanted to extend relativity to include all observers, whereas his special theory postulates only an equivalence among a limited class of observers—those who aren’t accelerating. A second reason was his concern with incorporating gravity, making use of what he called the equivalence principle, which postulates that observers can never distinguish the effects of gravity from those of acceleration as long as they observe phenomena only in their neighborhood. By this principle, he linked the problem of gravity with the problem of extending relativity to all observers. [...] Einstein was the only one who worried about these two problems. [...] in 1919. By that time, Einstein had invented his second theory of relativity, which he called general relativity. The experiment appeared to confirm the new theory’s predictions. The result was announced on the front pages of the world’s newspapers, making Einstein the first scientist to be a media star.

    General relativity is the most radical and challenging of Einstein’s discoveries—so much so that I believe the majority of physicists, even theoretical physicists, have yet to fully incorporate it into their thinking. The flashy stuff, like black holes, gravitational waves, the expanding universe, and the Big Bang are, it turns out, the easy parts of general relativity. The theory goes much deeper: It demands a radical change in how we think of space and time. [...] For Einstein, quantum physics was the essential mystery, and nothing could be really fundamental that was not part of the solution to that problem. Because general relativity didn’t explain quantum theory, it had to be provisional as well. It could only be a step toward Einstein’s goal, which was to find a theory of quantum phenomena that would agree with all the experiments and satisfy his demand for clarity and completeness. Einstein imagined for a time that such a theory could come from an extension of general relativity.

    [...] by the end of his life Einstein had to some extent abandoned his search for a unified field theory. He had failed to find a version of the theory that did what was most important to him, which is to explain quantum phenomena in a way that involved neither measurements nor statistics. In his last years he was moving on to something even more radical. He proposed giving up the idea that space and time are continuous. It is fair to say that while the idea that matter is made of atoms goes back at least to the Greeks, few before Einstein questioned the smoothness and continuity of space and time. To one friend, Walter Dallenbäch, he wrote, “The problem seems to me how one can formulate statements about a discontinuum without calling on a continuum as an aid; the latter should be banned from the theory as a supplementary construction not justified by the essence of the problem, which corresponds to nothing ‘real.’ ”

    However, Einstein made no progress with this new direction. He complained that “we still lack the mathematical structure, unfortunately.” To another friend, H. S. Joachim, he wrote: “It would be especially difficult to derive something like a spatiotemporal quasi-order from such a schema. I cannot imagine how the axiomatic framework of such a physics would appear, and I don’t like it when one talks about it in dark apostrophes. But I hold it entirely possible that the development will lead there.”
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  9. exchemist Valued Senior Member

    Ah OK I hadn't thought about superposition in that regard. I somehow doubt that superposition is a problem, as you only have superposition in a state that has not yet been determined. So it remains a statement of probability, rather than conflicting certainties. From the extract from Nolte's book thatMR originally quoted, I had thought it was wave-particle duality that was said to be the issue, i.e. a wave cannot be a particle and vice versa.

    P.S. I can't help thinking the Christian theologians must have tackled this in connection with the doctrine of the Trinity: How can one God consist of three persons: Father, Son and Holy Ghost? (When I was a student I used to think QM provided an insight into this paradox.)
  10. Magical Realist Valued Senior Member

    "Bose-Einstein condensate (BEC), a state of matter in which separate atoms or subatomic particles, cooled to near absolute zero (0 K, − 273.15 °C, or − 459.67 °F; K = kelvin), coalesce into a single quantum mechanical entity—that is, one that can be described by a wave function—on a near-macroscopic scale."==https://www.google.com/search?q=bos...9j69i57j0l4.1705j0j8&sourceid=chrome&ie=UTF-8

    Does this state contradict Aristotlean logic? How can something be many things and yet one thing at the same time?
  11. paddoboy Valued Senior Member


    Nice article, particularly the part highlighted. Thanks.
  12. Magical Realist Valued Senior Member

    Ofcourse, and as I have just noticed, the question of the OP goes directly to the philosophical distinction between the correspondence theory of truth (evidence) and the coherence theory of truth (logical consistency). Here's a description of those schools of thought:
    "The correspondence theory states that "a proposition must correspond with a fact or event" in order to be acknowledged as truth. For example, the statement "Hard work pays off" is an abstract assertion that would be true in the event a student performs well on a test after studying with focus and intensity. The statement, however, does not take into account other factors, such as influential teachers, clearly structured textbooks, or a manageable schedule. Nevertheless, the fact that the student performed well after applying hard work in an efficient manner is evidence that the statement must be true. Philosophy discusses the relationship between a proposition and fact: Either the proposition is true and is therefore supported by an existing fact in the world, or it is false and thus the fact used as a reference does not exist in the world..."

    ...The coherence theory "measures coherence and consistency among statements within a system." Thus, the coherence theory claims that a belief or statement is true if and only if it logically flows within other beliefs that together form a comprehensive interpretation of reality. This is synonymous with the Laws of Syllogism, which states that if p is equal to q, and q is equal to r, then p is equal to r. In other words, since the statement "all humans are mortal," the major premise, coherently aligns with the supporting minor premise "I am a human," one can deduce the conclusion "Therefore, I am a mortal." Attorneys and prosecutors base their argument on evidence as well as a premise reasoned from a systematic, underlying principle that gives credibility to his or her claim. For example, if a police officer claims that a person was drunk driving at 12 AM on Maple St, but the defendant shows documented evidence that he or she was present in a different city at that time, the incoherence of statements of the police officer is not sufficient evidence to prove his allegation."===https://www.wyzant.com/resources/bl...orrespondence_and_coherence_theories_of_truth
    Last edited: Apr 1, 2016
  13. DaveC426913 Valued Senior Member

    Remember what this thread is about: logic versus evidence.
    The example was entanglement.

    In a Newtonian universe, two particles should not be able to affect each other a million miles apart.
    It would be illogical to conclude that they could.

    Yet they do. So one would argue that entanglement is illogical.

    So if you don't embrace any new evidence, then your logic is based on outdated findings. You would see the entanglement experiments and call them a hoax.

    The only way to make any sense of the latest observations is to accept the new evidence, build a new model, whereupon the entanglement would be logical.

    So, yes evidence trumps logic.
  14. DaveC426913 Valued Senior Member

    This is science forum. The discussion that prompted the "outdated" was about entanglement. In those contexts, it is absolutely outdated.

    Your pool hall comment was a textbook red herring (not so much wrong as irrelevant).

    (Not to mention confusing Newton's Laws of Motion with a Classical Newtonian Universe)
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  15. iceaura Valued Senior Member

    As far as I follow, superposition is itself a state, that has been determined. It is mathematically described, and can be maintained (in theory) indefinitely.

    Not necessarily illogical - it would merely require a contradiction of one of the premises. As one of Newton's (hidden) premises is that Aristotelian logic is valid for describing the physical universe, that could be one of the premises contradicted, but there are other premises you might prefer to amend or discard. And even if you decide that is the one you want to drop, whether you want to describe the result as "illogical" depends on what you think about what replaced it - there are other forms of logic.

    The results of experiment conflict with the conclusions of Aristotelian logical deduction from Newton's or Einstein's premises. One has various options from there.
  16. Magical Realist Valued Senior Member

    Hey you're the one telling everyone that the logic of Newton's classical universe, which includes his laws, is outdated, not me:

    And as I have proven, you are totally wrong. You really should research an area of science before making sweeping generalizations about it.
    Last edited: Apr 2, 2016
  17. Daecon Kiwi fruit Valued Senior Member

    Darn, and I only just replaced my last irony meter...
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  18. Magical Realist Valued Senior Member

    Really? You're trolling my philosophy threads too now?
  19. DaveC426913 Valued Senior Member

    A little vocabulary help:
    You seem to misunderstand the word outdated.
    Our city subway system is outdated. It's small, slow, and prone to breakdown.
    Does that mean it can't carry most passengers? No. It simply means it does so insufficiently for our modern needs.
    Something being outdated does not mean it is entirely - or even mostly - useless.

    Got it?

    Newton's classical universe does not explain superposition (not to mention many other modern observations). It is outdated.
    It is not entirely useless, but it certainly is in the context in which it was brought up. i.e. superposition.

    Everything else you have followed up with is a red herring (not wrong, merely not relevant to the issue).
  20. Magical Realist Valued Senior Member

    Oh.."outdated" like the mini skirt? Ok..

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  21. river

    Logic vs evidence ....?

    Well certainly logic is an emotional response to evidence.

    For example UFO's

    Give all the thousands of examples for the evidence for the existence of UFO's and all you get is some uninformed idiot and actually some idiots are informed ; of which neither can reason it all out.

    These idiots have no logic nor are capable of logic; they are emotional ; their response to the over whelming evidence ; is emotional.
  22. river

    There is no logic vs evidence in the first place .

  23. paddoboy Valued Senior Member


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    Oh the irony of it all!

    Thousands of supposed UFO sightings, accounts of medical procedures by said Aliens, and still we have no hard evidence, nothing physical, no body or body parts, just the usual flittering in and flittering out exercises after travelling through interstellar space!
    I loved the mystery and awe that went with the TV series X-Files, but by the same token it should have had a "VBGIF" classification similar the the "G" classification, or the "AO" classifications. [Viewing by Gullible Idiots Forbidden]

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