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  1. #1
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    What is Logic? (Logic 101)

    This thread is a discussion about what logic is, its importance, how to use it, how "easy" it can be, and also to be used as a reference for other threads. A great book for further study of logic and its application is "Come Let us Reason" by Norman Geisler.

    First post: What is Logic?

    It is the function of the wise man to know order. - Aristotle

    Logic isn't really so tough. In fact, it's one of the simplest things to use because you use it all the time, though you may not realize it.

    When you are at a supermarket and one brand of sugar is 3 cents per ounce, but another is 39 cents per lb. It it doesn't take long for you to pull out your calculator. You do that because you recognize that those ounces and pounds have to be put in the same catagory to be compared. That's logic. You use logic to do most everything. When you decide to take a shower after you work out instead of before, you don't necessarily go through all the formal steps it takes to reach that conclusion validly, but your decision rests on logic nonetheless.

    Logic really means putting your thoughts in order.

    So lets see how order works...

    Order is the key word. It applies to all kinds of different disciplines. In nature, there is an order that reason discovers but does not produce. The patterns of quartz crystals, regularity of natural laws, movements of the planets, complext information in a single strand of DNA - they all show us an order that we can see but that we did nothing to put there, just as you are reading this post, but did not put the words here.

    In art however, we do produce order. The artist imposes order on the things around him. He crafts the lines he wants to see, bends steel to suit his purpose, arranges the rhythms, the melodies, the harmonies to express a certain feeling. Art is created by a person imposing order on the things of the external world.

    In philosophical thinking there is order also. Ethical order is order that reason produces in acts of the will. In other words, it is the ordering of our thoughts about the right and wrong of the things we choose. Whenever we ask a question about what we ought to do, we are ordering our choices by an ethical standard. That order tells us what we really think is good. It shows us what our values really are. Should I lie to save twenty bucks? Should I help the lady stranded on the freeway, or hurry home to watch football? How we answer depends on an ethical order that we produce about the choices we make. The best system of ethics is the one that best expresses the way things ought to be, ie., what really is good and valuable.

    The order of logic is very similiar. It, too, is an ordering that we produce, but it is concerned with ordering our thoughts. Logic is reason looking at itself to see how good reason works. It studies the methods that we use to analyze information and draw valid conclusions. It puts all of these methods into an order that gives us the right way to draw conclusions. The best system of logic is one that is best suited to drawing proper conclusions from the premises.

    To state this as a formal definition: Logic is the study of right reason or valid inferences and the attending fallacies, formal and informal.

    Let's break it up...

    Logic is the study of right reason. . . . That is the main point. Logic is a study, an ordering, of how to think rightly, or how to find truth. ie...logic is a way to think so that we come to correct conclusions..

    . . . or valid inferences. . . . That means implications. Part of studying logic is recognizing when A implies B and when it does not. There are clear-cut rules to help us with this.

    . . . and the attending fallacies, formal and informal. A fallacy is a mistake. Sometimes we make mistakes in the way we set up our thinking, or by using an implication that is not true. These are "formal fallacies", because they have to do w/ the form of the argument (more in a future post). Other times the mistakes are in the meaings of the terms we use. They might be unclear or misleading. Or, they might just not have anything to do with the subject at hand. Mistakes like these are "informal fallacies". Knowing the kinds of mistakes we can make helps us to avoid them.

    If we put all of our paraphrases together, we get a simplified definition: Logic is a way to think so that we can come to correct conclusions by understanding implications and the mistakes people often make in thinking.

    So regardless of the environment, circumstances, entities involved...logic is unchanging. While the variables may change, the way in that variables are determined to be true, untrue, valid or invalid do not change. Logic is is after all, putting our thoughts in order.

    Fallacies, form, syllogisms, and more will be in a future thread.
    Last edited by Apokalupsis; February 20th, 2004 at 03:08 PM.
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  2. #2
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    okay....I'm no scholar.....(ask ANYONE!).......but when I took a class called "Introduction to Logic" of which I for the most part hit on a couple of ladies during class while half-listening to the professsor.

    One thing he talked about really stuck with me over the years though. He was speaking about logic and how natural it is. But he also was saying that in spite of that, we, as civilized humans, often overlook or ignore that which is logical, valid or invalid or even obvious.
    To illustrate his point he gave us a bit of a riddle, or according to him, a logical set of guidelines that obviously lead to the only logical answer. We were quite perplexed as we all engaged in possible solutions to the problem. ( I even left the two young ladies alone for a while)

    We were told that if we followed what was logical, and determined what was valid, that the answer would present itself.

    We never figured out the answer of course, not in the course of that particular subject. We got the answer in bits and pieces as we would find time to bug our teacher about our conclusions. (guesses)

    anyway....if anyone is bored or simply cares to give the answer, heres the problem:

    You and your family are driving on a trip. You get to a fork in the road where a service station (that's a jiffy mart to you youngsters....*g*...)..is located right on the fork of the road.
    You do not know which road, the right or the left, is the correct road to take to reach your destination. You must remain in your car and wait until the attendent comes out to you car.
    Here is what you know about the service station:

    It is owned and operated by two twin brothers. they are identical twins. They dress alike, they talk alike, walk alike,etc; you CANNOT tell them apart in any way.

    You also know that one of the brothers lies ALL the time. He NEVER tells the truth. Conversely, the other brother has never told a lie. Not EVER.

    Only one brother will come out to the car. You and only you can ask the one that comes out only ONE question before deciding which way is the correct way to go.

    How would you be sure of knowing positively which way would be the correct way to go at the fork of the road?


    I gave this to a group of highschool kids with a 20 dollar incentive to solve it. They never really did, not without another hint, which was against the rules....*g*

    later taters....................:O)

  3. #3
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    Here is the answer in the "spoiler tag".


    Simply ask: "What path would your brother tell me to take to get to my destination?"

    You then take the OPPOSITE path.

    Reason:

    If the Truth brother is the one we have asked, he'll name the path truthfully that his lieing brother would tell us (so it can't be that path, it's a lie from his brother). Thus, choose the opposite path.

    If the Liar brother is the one we have asked, he'll tell us the opposite of the what his truthful brother would tell us...thus, choose that opposite path since it is the truth.

    Either way, it's the opposite path.
    Last edited by Apokalupsis; February 12th, 2004 at 07:30 PM.
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  4. #4
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    move to the head of the class...............*g*

  5. #5
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    /hands teacher shiny, red apple

    -=]Apokalupsis[=-
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    I never considered a difference of opinion in politics, in religion, in philosophy, as cause for withdrawing from a friend. - Thomas Jefferson




  6. #6
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    Logic is the corner stone of rationality and objectivity. Faith and hope along with belief and the like are irrational concepts and therefore cannot be totally logical in the scientific sense.

  7. #7
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    Re: What is Logic? (Logic 101)

    Quote Originally Posted by Apokalupsis
    Well...."common sense" can be subjective. Logical order, is absolute. There are strict laws or principles that one must adhere to, to be logical. We use most of these laws every day in normal thoughts and decisions, we just don't "think about it".

    I'm working on an introduction to logic part of the site that explains more.
    Dear Apok:

    I was talking to my friend and she says that she denies my laws of logic. How can I explain to her than logical order is not something which you can simply deny? She says that logic is man's creation and not absolute and we cannot use it to come to conclusions. I know she's wrong, but how do I explain it?

    Confused in Canada

  8. #8
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    Re: What is Logic? (Logic 101)

    Quote Originally Posted by starcreator
    Dear Apok:

    I was talking to my friend and she says that she denies my laws of logic. How can I explain to her than logical order is not something which you can simply deny? She says that logic is man's creation and not absolute and we cannot use it to come to conclusions. I know she's wrong, but how do I explain it?

    Confused in Canada
    I'm not Apok, but 1 + 1 will ALWAYS = 2, whether humans exist or not.

    BTW, are you sure you're not talking about Perv?

  9. #9
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    Re: What is Logic? (Logic 101)

    Quote Originally Posted by starcreator
    Dear Apok:

    I was talking to my friend and she says that she denies my laws of logic. How can I explain to her than logical order is not something which you can simply deny? She says that logic is man's creation and not absolute and we cannot use it to come to conclusions. I know she's wrong, but how do I explain it?

    Confused in Canada
    First of all, man discovered logic, not created it. We merely put into words that which we discovered. The way to prove this to your friend is through the use of "first principles" (laws of logic).

    Namely, the law of non-contradiction, law of excluded middle, and law of identity. Nearly all truths can be reduced to first principles. Have her "deny" the following (she won't be able to):

    Law of non-contradiction (or sometimes referred to as "law of contradiction" depending upon your prof)

    A cannot be both A and non-A at the same time in the same sense. Or, A is not non-A. Basically, no proposition can be both true and false at the same time.

    I cannot be both alive and dead at the same time in the same sense.


    Law of Excluded Middle

    A must be either A or not A; or either A or non-A.

    I must be either a human or not a human.


    Law of Identity

    A is A.

    A human is a human (not a cow).

    Use these examples or provide your own using these first principles of logic. These may seem quite simple and obvious...but you'd be surprised how often we miss them in more complex arguments (which is why it is good to try to slow down in a debate, and reduce the argument to its first principle when possible).
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  10. #10
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    Re: What is Logic? (Logic 101)

    Quote Originally Posted by Apokalupsis
    First of all, man discovered logic, not created it. We merely put into words that which we discovered. The way to prove this to your friend is through the use of "first principles" (laws of logic).
    /\

    The laws of logic are marvelous. By having her concede that the rules of logic are true her "argument" was worthless.

    Thanks,

    Star

  11. #11
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    Re: What is Logic? (Logic 101)

    What is logic? Logic is the science of thought, or alternatively science and scientific discipline set to thought. Like good science it it framed by rules.

    Like science it has its limitations, namely the limits of science and the limits of those rules. It too has it's 'theory' and its 'hypotheses'.
    Last edited by FruitandNut; October 10th, 2005 at 05:17 AM.
    "We don't see things as they are, we see them as we are." - Anais Nin.
    Emitte lucem et veritatem - Send out light and truth.
    'Fere libenter homines id quod volunt credunt' - Julius Caesar (rough translation, 'Men will think what they want to think')
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  12. #12
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    Re: What is Logic? (Logic 101)

    Quote Originally Posted by Apokalupsis View Post

    . . . and the attending fallacies, formal and informal. A fallacy is a mistake. Sometimes we make mistakes in the way we set up our thinking, or by using an implication that is not true. These are "formal fallacies", because they have to do w/ the form of the argument (more in a future post). Other times the mistakes are in the meaings of the terms we use. They might be unclear or misleading. Or, they might just not have anything to do with the subject at hand. Mistakes like these are "informal fallacies". Knowing the kinds of mistakes we can make helps us to avoid them.
    ...a false or faulty premise, this is where many arguments can go wrong or become much weaker. A person will insist their argument is very strong based on the logical argument or syllogism itself. But, if the the fundamental premises/assumptions/evidence are faulty or very subjective in unto themselves then the logical argument is very suspect and weak based on the internal components contained inside the syllogism.
    Liberty: One of Imagination's most precious possessions.
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    Love: A temporary insanity curable by marriage. ---Ambrose Bierce

  13. #13
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    Re: What is Logic? (Logic 101)

    Logic will always be boxed in by the constraints of human knowledge and understanding.
    "We don't see things as they are, we see them as we are." - Anais Nin.
    Emitte lucem et veritatem - Send out light and truth.
    'Fere libenter homines id quod volunt credunt' - Julius Caesar (rough translation, 'Men will think what they want to think')
    Kill my boss? Do I dare live out the American dream? - Homer Simpson.

  14. #14
    Ishkabob
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    Re: What is Logic? (Logic 101)

    Quote Originally Posted by Apokalupsis View Post
    Here is the answer in the "spoiler tag".


    Simply ask: "What path would your brother tell me to take to get to my destination?"

    You then take the OPPOSITE path.

    Reason:

    If the Truth brother is the one we have asked, he'll name the path truthfully that his lieing brother would tell us (so it can't be that path, it's a lie from his brother). Thus, choose the opposite path.

    If the Liar brother is the one we have asked, he'll tell us the opposite of the what his truthful brother would tell us...thus, choose that opposite path since it is the truth.

    Either way, it's the opposite path.

    I think your solution doesn't solve the problem.

    "...Conversely, the other brother has never told a lie. Not EVER."

    Just because he has never told a lie, doesn't mean he can't.

  15. #15
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    Re: What is Logic? (Logic 101)

    Not so. And it isn't my problem. It was asked by another member, CC.

    Note the key part of the problem here:

    You also know that one of the brothers lies ALL the time. He NEVER tells the truth. Conversely, the other brother has never told a lie. Not EVER.

    The words/phrases "all the time", "never", "not ever" tells us that this isn't just an issue of the past, but of also present and future.
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  16. #16
    buzz123
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    Re: What is Logic? (Logic 101)

    Isnt logic a way to gain commonsense/

  17. #17
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    Re: What is Logic? (Logic 101)

    Logic is common snse, and common sense is knowledge, therefore knowledge is logic, but knowledge is in the eye of the beholder, therefore logic is based off everyone around you who considers yousmart or dumb

  18. #18
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    Re: What is Logic? (Logic 101)

    { It is a percieved rational sequencing of thoughts, facts and information.
    "We don't see things as they are, we see them as we are." - Anais Nin.
    Emitte lucem et veritatem - Send out light and truth.
    'Fere libenter homines id quod volunt credunt' - Julius Caesar (rough translation, 'Men will think what they want to think')
    Kill my boss? Do I dare live out the American dream? - Homer Simpson.

  19. #19
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    Re: What is Logic? (Logic 101)

    Fruitnnut:I agree
    to further your definition: if a group of people who think differently about what is logial, then they the next generation differently proving that logic can be changed to a degree

  20. #20
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    Re: What is Logic? (Logic 101)

    Quote Originally Posted by Apokalupsis View Post
    First of all, man discovered logic, not created it. We merely put into words that which we discovered. The way to prove this to your friend is through the use of "first principles" (laws of logic).

    Namely, the law of non-contradiction, law of excluded middle, and law of identity. Nearly all truths can be reduced to first principles. Have her "deny" the following (she won't be able to):

    Law of non-contradiction (or sometimes referred to as "law of contradiction" depending upon your prof)

    A cannot be both A and non-A at the same time in the same sense. Or, A is not non-A. Basically, no proposition can be both true and false at the same time.

    I cannot be both alive and dead at the same time in the same sense.


    Law of Excluded Middle

    A must be either A or not A; or either A or non-A.

    I must be either a human or not a human.


    Law of Identity

    A is A.

    A human is a human (not a cow).

    Use these examples or provide your own using these first principles of logic. These may seem quite simple and obvious...but you'd be surprised how often we miss them in more complex arguments (which is why it is good to try to slow down in a debate, and reduce the argument to its first principle when possible).
    How are you so certain that she won't be able to deny these first principles? I'm asking this because at the moment, the only reason why I take such principles as being valid is because they are extremely intuitive to me and I cannot imagine things not being such. But my inability to see something doesn't mean it's automatically not the truth, is it?

    It seems to me that logic is the resulting model of man's interpretation of the universe. Man did not create it from scratch, but man derived it from observations, intuitions, and experiences as seen from man's perspective. The logic model is of great use to us and it hasn't failed us yet, but I don't see how we can ascertain its ultimate validity given our human limits.

 

 
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