Oct 1, 2006 - Logic and Argumentation

Oct 1, 2006 - Logic and Argumentation
- Introduction
  - Bad arguments
    - Einstein was a genius, geniuses need sleep, I need sleep, therefore I am Einstein
  - What is logic?
    - The art of reasoning
    - Taking info and drawing conclusions
  - Today's class
    - We will focus on analysis
      - We are not logicians
      - We are likely not in the business of setting up arguments for others to analyze
- Inductive
  - "arguing by example to probable conclusions"
  - Form
    - Specific observation
    - Generalization or simple induction
  - Example
    - Most people who have experience with motorcycles recommend them for commuting
    - I should use a motorcycle for commuting
  - Not certain, so you tend to spend time strengthening the argument
  - How to strengthen
    - Provide more examples
      - Here I would name some names if it made any difference
    - Identify relevant similarities between supporting examples
      - All the provided examples (if I'd provided any) understand motorcycle riding and all the safety issues.. they're not just adrenaline-seeking young 'uns
    - Observe possible counterarguments and show how they don't affect the conclusion
      - Motorcycle accidents statistically yield a higher fatality rate, but the vast majority of those accidents are caused by preventable things, like alcohol, excessive speed, not paying attention
    - Provide supporting arguments
      - Motorcycles get excellent gas mileage
      - Motorcycles are fun
      - Motorcycles are relatively cheap to purchase
      - Motorocycles emit much less pollution per commuter than cars
- Deductive
  - "arguing by axioms to valid conclusions"
  - Draw up square
  - If P then Q
    - P is sufficient condition
    - Q is necessary condition
  - Modus ponens
    - Form
      - If P, then Q
      - P
      - Therefore Q
    - Example
      - Declaration of Independence
  - Modus tollens
    - Form
      - If P, then Q
      - not Q
      - Therefore not P
    - Example
      - If there is a fire, then there will be smoke
      - There is no smoke
      - Therefore there is no fire
  - Reductio ad absurdam
    - "Reduction to absurdity"
    - Taking the roof off
    - Prov 26:4-5
      - Do not answer a fool according to his folly, Lest you also be like him. Answer a fool according to his folly, Lest he be wise in his own eyes.
    - Form
      - Assume the opposite
      - Show how it leads to absurdity
      - Assert conclusion
    - Example
      - You say that all knowledge is derived from sensory perception and experimentation
      - Well, let's assume you're right for a moment.
      - How would you prove the following assertion: "all knowledge is derived from sensory perception and experimentation"?
      - If you would prove it using sensory perception and experimentation, wouldn't you be begging the question?
      - If you say it's a fundamental assumption, aren't you denying what you already claimed?
    - Characteristics
      - Useful for debate, apologetics because it's easy to follow
      - It's also a great place for asking questions
      - Presuppositional arguments often take this form
        Assume a naturalistic worldview for a second...
- Fallacies
  - Affirming the consequent
    - Form
      - If P, then Q
      - Q
      - Therefore P
    - Example
      - If I am human, then I am mortal
      - I am mortal
      - Therefore I am human
  - Denying the antecedent
    - Form
      - If P, then Q
      - not P
      - Therefore not Q
    - Example
      - If something is a dog, then it is mortal
      - But I'm human
      - Therefore I'm not mortal
  - Ad hominem
    - Form
      - A makes proposition P
      - There is something objectionable about A
      - Therefore P is false
    - We need to watch this one.. it comes up often in creation vs evolution debates
    - Example 1
      - You say that Bob is innocent
      - But you're a criminal yourself
      - Therefore Bob isn't innocent
    - Example 2
      - You say that people should commute on motorcycles
      - But you sell motorcycles
      - So of course you'd say that (people shouldn't necessarily commute on motorcycles)
    - Poisoning the well
      - Dr Stein claims that there is no God
      - But Dr Stein's expertise is in the control of ovarian maturation in Japanese quail
      - So why should we believe his argumentation?
  - Genetic fallacy
    - Form
      - Idea P came from idea A
      - A is bad/false/wrong
      - Therefore P is wrong
    - Example
      - Philosopher Peter Singer states that affluent nations should do their best to take in as many refugees as they can hold
      - But Peter Singer is in favor of abortion, infanticide and euthanasia
      - Therefore affluent nations have no obligation to take in refugees
  - Straw man
    - Form
      - Person A argues for P (when, in fact, A argues no such thing)
      - P is wrong for such and such a reason
    - Example
      - TODO