Logic 101 lecture 2

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Lecture 2 - Fallacies of Relevance

Transcript of Logic 101 lecture 2

  • 1. Lecture 2 Fallacies of Relevance
    Logic 101 Lecture 2
  • 2. Reasoning meant to convince someone of something
    which is not necessarily angry, impassioned, or loud
    What is an argument?
  • 3. Deduction
    Completely infallible proof
    Either Obama or McCain is president.
    McCain is not president.
    Therefore, Obama is president.
    Induction
    Very veryvery likely to be true, but not necessarily true
    Either Obama or McCain will be president.
    Obama holds a 53% majority with 95% of precincts reporting
    Therefore, Obama will be president.
    Types of Logic
  • 4. Validity
    If the premises of the argument are true, the conclusion must be true
    If I drink the arsenic, it will kill me. Therefore, it is lethal.
    This doesnt care about whether or not they are ACTUALLY true
    The arsenic is lethal whether or not I drink it
    Soundness
    Valid argument w/ true premises
    What makes an argument good?
  • 5. Errors in inductive reasoning
    May or may not be deductively true, but they are regardless invalid and not good logic
    Lots of gray areas
    These are patterns of reasoning that oftenfail- but these patterns may hold truth
    It is up to you to be able to tell the difference
    Informal Fallacies
  • 6. Arguments that fail because of a lack of connection between premises and conclusion
    Fallacies of Relevance
  • 7. Dr. Bradshaw: It appears that my colleagues theory holds some weight. However, a little research shows that the theory of gravitation she is championing was first created by alchemists.
    AngryPundit422: Arizona politicians say that they are trying to protect our countrys interest by checking immigration status, but is there anything more Nazi-like than saying papers, please?
    Genetic Fallacy
  • 8. Attacking the (perhaps dubious) origins of an argument instead of the argument itself.
    Nazis?
    Alchemists?
    (Fun fact of the day: Issac Newton was originally an alchemist- he wrote much more about alchemy than he did about physics)
    If the argument is valid, it does not matter where it came from. Valid argument is valid.
    Genetic Fallacy
  • 9. Anderson: Recently, Bradshaw has argued that the theological framework expressed in the Bible was a new development in the Mediterranean area. However, a careful examination of the historical precedents shows that all of the elements of this framework had been around for centuries in various cultures around or near the Mediterranean.
    Genetic Fallacy
  • 10. David: Barbara would like to argue that we should stop cutting down trees in the rain forest, as it would be damaging to our environment. However, Barbara took an IQ test last week and it came up negative.
    Edgar: In addition, one can easily recall that, during last election, Barbara donated $10,000 of her companys money to the Communist party.
    Frank: And dont forget that Barbaras husband owns a large northeastern logging company, and would stand to benefit greatly if the rain forest is protected from logging operations.
    Ad Hominem
  • 11. Attacking the person making the argument instead of the argument itself. (Latin against the person)
    Abusive just plain being mean
    Associative implying the arguer associates with unpopular or undesirable people or groups
    Circumstantial citing (perhaps legitimate) ulterior motives
    Again, if the argument is valid, none of this matters.
    Maybe it would be wise to double-check the reasoning or the data, but it doesnt invalidate the argument.
    Ad Hominem
  • 12. Senator Hamm: My opponent claims that he should be elected on the basis that he is unbiased and would help to ease racial tensions in our district. However, you may recall that he was the driving force behind the resurgence of the Neo-Nazi party in last terms election.
    Ad Hominem
  • 13. George: My opponent claims that I have accepted donations from lobbying groups that will influence my voting as a Congressman. However, my opponent has taken just as much, if not more, in donations from several other prominent lobbying groups.
    Ad Hominem TuQuoque
  • 14. Claiming the argument applies to the arguer as well (Latin you too)
    Two wrongs dont make a right, and logic doesnt care about hypocrisy.
    Again, if youre right, youre right. Notice the pattern yet?
    Just because you make a valid point about something doesnt mean it negates the original argument
    Ad Hominem TuQuoque
  • 15. Announcer: Over 30 million people own a Chevy. Do they know something you dont?
    Perry: You should join my golf club. Its the most exclusive in the state.
    Ad Populam
  • 16. Citing somethings popularity as an argument (Latin to the people)
    Band-wagoning: high popularity = good
    Snobbery: low popularity = good
    Incorrect logic knows no population limit (unfortunately)
    Ad Populam
  • 17. Horace: Im sorry I was going 72 in a 55, officer, but I wasnt speeding! My alarm clock didnt go off, there was no hot water in the shower, my baby was up crying all night, and if Im late to work one more time Im going to get fired!
    Ivan: My friend Horace here was not speeding. If you give him a ticket, youll make me angry, and you wouldnt like me when Im angry.
    Appeal to Pity / Force
  • 18. Everyone has a sob story, and even if they do, its no excuse. Stephen Chbosky, The Perks of Being A Wallflower
    Maybe the story will pull some heartstrings, but you were still breaking the law.
    On the other hand, beating somebody up may make them let you have your way, but it sure doesnt change the logic.
    Appeal to Pity / Force
  • 19. Horace: You should not give me this ticket. I am a very influential man, and I can have funding for the police department withdrawn for a very long time.
    This sounds like an appeal to force, but the conclusion is you should not give me this ticket, not that Horace wasnt guilty of speeding. It may actually be in the officers best interest to let Horace off.
    Appeal to Pity / Force
  • 20. Jules: Some people believe the government should legalize marijuana. However, government endorsement of drug use will lead to a rapid increase in drug abuse, causing the costs of drug treatment and rehab centers to skyrocket, ultimately draining our already-strained economy.
    Kelly: I wore this outfit because you told me that you liked it the last time I wore it. You didnt notice me wearing it today. I knew it! You think Im ugly!
    Straw Man
  • 21. Addressing a weaker argument that is superficially related to the argument at hand.
    Legalizing pot is not the same thing as endorsing it
    Wearing a nice outfit doesnt make you attractive (or mean he was even commenting on your attractiveness)
    Straw Man