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The essence of logic is to find out what argumentative structures

  1. Mar 7, 2003 #1

    Tom Mattson

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    This will be the new version of my "Logic" thread in PF v2.0. I'll get my logic notes pasted into this forum ASAP, along with some of the more useful discussion from the old thread.
     
    Last edited by a moderator: Feb 4, 2013
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  3. Mar 7, 2003 #2

    Kerrie

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    i did not read through every single post of your last thread on logic tom, however, it would seem "right" to me that logic is subjective, at least when i am referring to the reasoning and rationalizing form of logic...
     
  4. Mar 9, 2003 #3

    ahrkron

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    I disagree. In a sense, the essence of logic is to find out what argumentative structures can definitely be "trusted" regardless of content, so that arguments can be analysed independently of how you "feel" about the conclusion they seem to produce.
     
  5. Mar 9, 2003 #4

    Kerrie

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  6. Mar 17, 2003 #5
    We have learned logic from the way the universe works. We are mimicing what we see in the sequence of events with which the universe unfolds.

    We have called logical sequence "logical sequence" in an attempt to harness the incredible logic witnessed in the structure and efficency of the universe.

    Thats what I think about logic.
     
  7. Mar 17, 2003 #6
    "I know what you're thinking about," said Tweedledum: "but it isn't so, nohow."
    "Contrariwise," continued Tweedledee, "if it was so, it might be; and if it were so, it would be; but as it isn't, it ain't. That's logic."
     
  8. Mar 17, 2003 #7

    Tom Mattson

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    Hey folks, glad to see you all talking. My notes are coming up, slowly but surely, here:

    https://www.physicsforums.com/showthread.php?s=&threadid=111

    It is taking me a little while to translate all the color and smiley brackets to the new forum.

    The more meaningful discussion in the PF v2.0 version of this thread centered on...

    1. The Principle of Charity
    This is an admonishment to make another person's argument as good as possible. This means, first and foremost, try to make the argument deductively valid whenever possible. If not possible, then try to make the argument a strong inductive argument. A strong inductive argument is preferable to a valid deductive argument with questionable premises.

    Why do all this? Because the whole point of debate is to learn, not to be agreed with. If you make your opponent's argument as good as possible and, in the process, discover that he is correct, then you have learned something. If, on the other hand, you discover that his best argument is fallacious, then again, you have learned something.

    2. The Difference Between Deductive and Inductive Arguments.
    This was done via exercises that I posted. Audacity Dan posted his solutions, but unfortunately I did not copy them.
    :frown:

    I'll put the exercises back up shortly, along with the rest of my notes.
     
  9. Mar 17, 2003 #8

    Les Sleeth

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    Excellent. I agree logic "works" because it reflects the order/symetry of the universe. It is the same quality that allows math. It works with everything . . . except that which isn't within the boundaries of order and symetry.

    By the way, what turned you quantum? Photon bombardment? Blackbody abuse? H????????????
     
  10. Mar 17, 2003 #9
    Like anything else, logic depends upon context. For example, the liars paradox:

    "Everything I say is a lie."

    Makes perfect sense if everyone who hears it knows you happen to be a chronic liar. Strictly logically speaking, however, it makes no sense whatsoever. Thus, even whether or not we should use of logic depends upon the context. This also applies to how you "feel" about the conclusions of logic. The context can over-rides the content of logic and, in fact, whether something is consider a content or context just depends on how you want to look at it.

    Therefore the essense of logic is not so much to find out what argumentative structures can be trusted, but more how it fits into the various contexts life presents us. That is of course not to downgrade the incredible usefulness of logic for making sure your check book is balanced or whatever. Just to put it in perspective.
     
  11. Mar 17, 2003 #10
    Tom, that is a good reading! I really like the slow going through definitions. I think its so important to stop and define every word we use before continuing with a discussion so that there is a common ground for the participants to work. Its (yes) very logical.

    I am still convinced that if a logic does not reflect, in every detail, a law or a state that exists in nature, then it is faulty logic and will not stand up to the rigors of time or scrutiny.

    Here we are, members of an intricate existence, witnessing the precision and the efficiency of nature supporting our being. How can we not have learned logic from the lessons in nature that we study.

    The more we study nature, the more complex and in depth our reasoning becomes and the more stable our logic.
     
    Last edited: Mar 17, 2003
  12. Mar 17, 2003 #11
    Nice to see the most important thread for the philosophy forum reinstated. I love the new look.
     
  13. Mar 18, 2003 #12

    Tom Mattson

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    I've finished posting my Chapter 0 notes. I'll repost the exercises in this thread, in case anyone wants to take a crack at them. My notes for Chapter 1 are also finished, but I'll give everyone a little time to catch up first. By staying a chapter ahead of you, I hope the progression won't be as jerky this time out.

    https://www.physicsforums.com/showthread.php?s=&threadid=111
     
  14. Apr 3, 2003 #13

    Tom Mattson

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    In PF v2.0, I posted some exercises to reinforce the material covered in the notes. Audacity Dan (now Dissident Dan) posted his solutions to the first set. If you would like to see them, then cough up the $20 for the archive CD.

    Here are some exercises that cover Chapter 0 pretty comprehensively.

    Disproof by Counterexample
    Each of the following deductive arguments is invalid. Provide a counterexample for each.

    Argument 1:
    All paramecia are single-celled organisms.
    No sea urchins are paramecia.
    Therefore, no sea urchins are single-celled organisms.

    Argument 2:
    Some Englishmen are Protestants.
    Winston Churchill was a Protestant.
    Therefore, Winston Churchill was an Englishman.

    Argument 3:
    If an animal is a mammal, then it bears its young live.
    A gorilla bears its young live.
    Therefore, a gorilla is a mammal.

    Argument 4:
    Some dogs are good pets.
    Some dogs are terriers.
    Therefore, some terriers are good pets.

    The above exercise set sparked some interesting conversation in PF v2.0. The noteworthy thing about these arguments is that, although they are invalid, every statement in them is true! This highlights the necessity of logical rigor.

    Deductive or Inductive?
    Examine each argument below. Is the argument deductive or inductive? Explain.

    Argument 1:
    All human choices are determined, since all events in the universe are determined and all human choices are events in the universe.

    Argument 2:
    All birds can fly. I’ve never seen one that can’t.

    Argument 3:
    Today is Wednesday. You came 4 days ago, so that means you came on Saturday.

    Argument 4:
    I sent her the letter 3 weeks ago and have still received no answer; therefore, my letter must have been lost in the mail.

    Argument 5:
    A=B and B=C, therefore A=C.

    Argument Analysis and Charity
    Assuming ordinary context, examine each of the following arguments. Identify the conclusion and the premises, and supply a missing premise that would make the argument deductively valid.

    Argument 1:
    Bats are not birds, because birds have feathers.

    Argument 2:
    The baseball game was dull, since both teams played poorly.

    Argument 3:
    This liquid is not acid, for the litmus paper we placed in it did not turn red.
    Argument 4:
    He passed the examination; therefore, he must have lied.

    My first set of notes for Chapter 1: Categorical Statements is now up.
     
  15. Apr 4, 2003 #14
    All cattle are animals.
    No cats are cattle.
    Therefore, no cats are animals.

    Some people use logic.
    Lifegazer is a person.
    Therefore, Lifegazer uses logic...I couldn't help it. I'm so rude. That was uncalled for.

    If a lifeform is a plant, then it reproduces.
    A human reproduces.
    Therefore, a human is a plant.

    Some oranges are rotten oranges.
    Some oranges taste good.
    Therefore, some rotten oranges taste good. (Granted, this is a tad bit subjective but...)

    Take care. --Carter
     
  16. Apr 4, 2003 #15

    Tom Mattson

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    LOL

    Alas, in your zeal, you got this one wrong. The predicate term of the first two premises ("people who use logic") should be the same, as it was in the original argument, whose schema is:

    Some p are q.
    r is a q.
    Therefore, r is a p.

    Otherwise, good job.

    Tom
     
  17. Apr 4, 2003 #16
    That guy was voted Britain's greatest hero. So thanks CJ. :wink:
     
  18. Apr 4, 2003 #17

    Tom Mattson

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    Kerrie, could you split off the "Quantum Mechanics vs. Logic" posts into a separate thread? (It starts with heusdens' first post).

    Thanks,
     
  19. Apr 4, 2003 #18

    Tom Mattson

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    Back to the topic...

    I will post more of the Chapter 1 notes tomorrow. I was holding off on it because it is about Venn diagrams. Since I cannot make those in this forum, I thought I had to skip it and go directly to the part on immediate inferences.

    Then I found this website:
    http://www.venndiagram.com

    Neato.
     
  20. Apr 5, 2003 #19
    that is not an easy one to explain but i will give it a try, hopefully most people will agree with this explanation:

    ideally, logic is objective; however, our perceptions are bound to be subjective due to our nature as individuals. so in practice, logic is objectivity used as a tool to lessen the effects of our inherent subjectivity.


    does that seem logical to everyone?
     
  21. Apr 14, 2003 #20
    oops

    I seem to have left this topic in the duff.

    Sorry about that.

    When a person feels bad about leaving a topic in the duff they are sorry.

    When a treeplanter leaves a seedling behind they leave it in the duff.

    There for, treeplanters are sorry by up to 600 times a day.


    Tom, this is good learning...
    must find time...
    must learn...
    I learnink...
    must spend more time learning...
    must read logic topic more often...
     
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