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Thread: Deductive Logic, Inductive Logic, and Logical Fallacies

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    Member Trodon's Avatar
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    Lightbulb Deductive Logic, Inductive Logic, and Logical Fallacies

    This is an excellent introduction to deductive logic, inductive logic, and logical fallacies. When I was in college I took a course on symbolic logic. It did me less good than this website. This gives good information to use in forum debates (which all too often become insult contests. ).

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    A deductive argument is an argument such that the premises provide (or appear to provide) complete support for the conclusion...

    A good deductive argument is known as a valid argument and is such that if all its premises are true, then its conclusion must be true...

    A good inductive argument is known as a strong (or "cogent") inductive argument. It is such that if the premises are true, the conclusion is likely to be true...

    A fallacy is, very generally, an error in reasoning. This differs from a factual error, which is simply being wrong about the facts.
    http://www.nizkor.org/features/fallacies/

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    In political and religious arguments most reasoning seems to be inductive.

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    So you think that religious arguments are "likely to be true"?

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    Quote Originally Posted by ryan View Post
    So you think that religious arguments are "likely to be true"?
    The doctrines of the various religions contradict, so they cannot all be true.

    Religious arguments are only fruitful when they make assertions that can be verified, such as: The first verse of the Gospel of Mark asserts that Jesus is the Messiah and the Son of God.

    One can assert that various passages in the New Testament assert that those who believe in Christian doctrines and obey Christian moral teachings will go to Heaven.

    One cannot assert that they really will go to Heaven, however.

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    Quote Originally Posted by Trodon View Post
    This is an excellent introduction to deductive logic, inductive logic, and logical fallacies. When I was in college I took a course on symbolic logic. It did me less good than this website. This gives good information to use in forum debates (which all too often become insult contests. ).

    --------

    A deductive argument is an argument such that the premises provide (or appear to provide) complete support for the conclusion...

    A good deductive argument is known as a valid argument and is such that if all its premises are true, then its conclusion must be true...

    A good inductive argument is known as a strong (or "cogent") inductive argument. It is such that if the premises are true, the conclusion is likely to be true...

    A fallacy is, very generally, an error in reasoning. This differs from a factual error, which is simply being wrong about the facts.
    http://www.nizkor.org/features/fallacies/

    --------

    In political and religious arguments most reasoning seems to be inductive.
    Me I thought that all arguments apparently concluding on an actual fact were essentially inductive. So this would also be true of science for example.
    EB

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    Member Trodon's Avatar
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    Quote Originally Posted by Speakpigeon View Post
    Quote Originally Posted by Trodon View Post
    This is an excellent introduction to deductive logic, inductive logic, and logical fallacies. When I was in college I took a course on symbolic logic. It did me less good than this website. This gives good information to use in forum debates (which all too often become insult contests. ).

    --------

    A deductive argument is an argument such that the premises provide (or appear to provide) complete support for the conclusion...

    A good deductive argument is known as a valid argument and is such that if all its premises are true, then its conclusion must be true...

    A good inductive argument is known as a strong (or "cogent") inductive argument. It is such that if the premises are true, the conclusion is likely to be true...

    A fallacy is, very generally, an error in reasoning. This differs from a factual error, which is simply being wrong about the facts.
    http://www.nizkor.org/features/fallacies/

    --------

    In political and religious arguments most reasoning seems to be inductive.
    Me I thought that all arguments apparently concluding on an actual fact were essentially inductive. So this would also be true of science for example.
    EB
    That's a tough one. Absolute certainty only exists in mathematics. Near certainly only exists in the experimental sciences, where hypotheses can be tested with controlled, repeatable experiments.

    In political science people develop strong beliefs that cannot be verified absolutely, only indicated.

    For example, Democrats blame Republican economic policies for the Great Depression. Republicans blame the duration of the Great Depression on the economic policies of the Roosevelt administration.

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    Member Trodon's Avatar
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    An example of deductive logic is:

    Major Premise - During the American Civil War states to the north of the Potomac River supported the Union.

    Minor Premise - Massachusetts is to the north of the Potomac River.

    Conclusion - Therefore, Massachusetts supported the Union.

    An example of inductive logic is:

    Major Premise - In the United States states to the north of the Potomac River usually have cooler weather than states to the south of the Potomac River.

    Minor Premise - Massachusetts is to the north of the Potomac River. Mississippi is to the south of the Potomac River.

    Conclusion - Therefore right now the temperature in Massachusetts is probably cooler than the temperature in Mississippi.

    There have probably been times when it rained in Massachusetts and snowed in Mississippi, but these times have been rare.

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    Quote Originally Posted by Trodon View Post
    That's a tough one. Absolute certainty only exists in mathematics.
    You're just a Boltzmann brain imagining that the axioms of arithmetic imply 1+1=2.

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    According to an article that appeared in The Wall Street Journal, from the presidencies of Harry Truman to that of George W. Bush there have nearly always been more jobs created per year under Democratic presidents than Republican presidents.

    http://blogs.wsj.com/economics/2009/...ord-on-record/

    According to another article that appeared in The Wall Street Journal, since 1900 there has nearly always been more growth in the stock market under Democrat presidents.

    http://blogs.wsj.com/marketbeat/2012...an-for-stocks/

    It would be an inductive argument to claim that Democratic economic policies are better for the job market and the stock market than Republican economic arguments. It is conceivable that other factors were critical.

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    Quote Originally Posted by Trodon View Post
    An example of deductive logic is:

    Major Premise - During the American Civil War states to the north of the Potomac River supported the Union.

    Minor Premise - Massachusetts is to the north of the Potomac River.

    Conclusion - Therefore, Massachusetts supported the Union.

    An example of inductive logic is:

    Major Premise - In the United States states to the north of the Potomac River usually have cooler weather than states to the south of the Potomac River.

    Minor Premise - Massachusetts is to the north of the Potomac River. Mississippi is to the south of the Potomac River.

    Conclusion - Therefore right now the temperature in Massachusetts is probably cooler than the temperature in Mississippi.

    There have probably been times when it rained in Massachusetts and snowed in Mississippi, but these times have been rare.
    If you include probabilities or even mere likelihoods in your argument then it can become a deductive argument. All you need is to make sure that the conclusion does reflect properly the probabilities or likelihoods indicated in the premises.

    Americans are more likely than Europeans to shoot their neighbour
    Gustaf Glamuresky is an American
    Therefore Gustaf Glamuresky is more likely than Europeans to shoot his neighbour


    EB

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    College Is a Fraud If It Doesn't Refute Marbury v. Madison As Begging the Question

    Quote Originally Posted by Trodon View Post
    This is an excellent introduction to deductive logic, inductive logic, and logical fallacies. When I was in college I took a course on symbolic logic. It did me less good than this website. This gives good information to use in forum debates (which all too often become insult contests. ).

    --------

    A deductive argument is an argument such that the premises provide (or appear to provide) complete support for the conclusion...

    A good deductive argument is known as a valid argument and is such that if all its premises are true, then its conclusion must be true...

    A good inductive argument is known as a strong (or "cogent") inductive argument. It is such that if the premises are true, the conclusion is likely to be true...

    A fallacy is, very generally, an error in reasoning. This differs from a factual error, which is simply being wrong about the facts.
    http://www.nizkor.org/features/fallacies/

    --------

    In political and religious arguments most reasoning seems to be inductive.
    "Fallacy" is a misleading term. It should be admissible evidence. Its only fault is that it is not necessarily conclusive. However, it is probably conclusive. For example, post hoc, propter hoc. If you suddenly have a new problem, the usual cause is something you've been doing differently lately. You should take positive action to change that and you will probably cure the problem.

    Second, a "fallacy" can be taken as a clue to what or who should be investigated first. That is most likely to lead to conclusive evidence or more pieces of evidence leading to a convincing causal statement. So, even if a narrow-minded judge plays silly Gotcha games with "fallacies," you could use them beforehand to come up with something unobjectionable through investigation.

    The case where a fallacy is most often actually false is when a question is begged, such as "God wouldn't let us believe in Him if He didn't exist" or "Homosexuality is obviously a sexuality or it wouldn't be called homosexuality" or "We interpret the Constitution as giving us the right to interpret the Constitution."

    "Question" is merely something sought (a quest) as a conclusion; it is not interrogative. "Begging" is asking for something that is not yours by right. Diploma Dumbos prove how meaningless college education is when they lazily assume that "beg the question" means "which leads to the question."

    On-air airheads might say, "Schwartzenegger wants to run for President, which begs the question, 'Who will he pick as his running mate?'" or "How much of his own millions will he use?' when the only question it begs is that he is disqualified because he was born in Austria to Austrian parents.

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