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3.4 Fallacies in Logic

3.4 Fallacies in Logic
  • Math Help

    The fallacy of  "non sequitur" or "false cause" is common.

    Premise: P implies Q. Government funding for police, schools, and roads is necessary.
    Premise: P implies R. Government funding for police, schools, and roads comes from taxes.
    Conclusion: R implies Q. Therefore, taxes are necessary. 

    Do you see why this type of fallacy is called "It does not follow"?

    The point of Example 3 is that a set diagram can help when trying to analyze a syllogism.

    Oddly enough, when you believe that a syllogism has reached a valid conclusion, it is tempting to not think as clearly. When you are analyzing a syllogism, try to divorce yourself from whether the conclusion is true or false.

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  • Checkpoint Solution

    Here is the original statement.

    Our society is filled with violence, and there is a lot of violence on TV. It follows that the violence in society is caused by people watching TV.

    Here is a possible set diagram for this argument.

  • Comments (2)

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    system user
    Ron Larson (author)1 decade ago |
    Thanks for posting this comment. I agree that the "fallacy of false cause" is common.
    system user
    Guest   1 decade ago |
    This is a common fallacy in statistics. It is sometimes summarized as "Correlation does not imply Causality." Here is an example. It is claimed by some people that severe illness is caused by depression and anger. After all, people who are severely ill are very often depressed and angry. Thus, it follows that the cause of severe illness actually is the depression and anger. So, a good and cheerful attitude is key to staying healthy.