Lecture Notes.
 
  

 
Module Four: Session Three

Basics of Truth

  • Critical thinkers want to know what is true. That's the whole point of reasoning. In this section you will learn what the word "truth" means, what knowledge is and how it differs from opinion. You will also learn how to properly categorize sentences so you can know how to evaluate them.

Properties of Claims

  • Every claim has four attributes, the first three of which must be determined before reasoning. The fourth attribute is determined by reasoning.

Descriptive and Prescriptive Claims

  • Every claim is either descriptive or prescriptive.
  • Descriptive claims tell how the world is, was, or will be.
  • Example: "Bob is friendly." This sentence describes how the world (Bob being part of the world) is.
  • Example: "Texas was once a sovereign nation." This sentence describes how the world used to be.
  • Prescriptive claims tell how the world should be. (This includes all possible time frames.)
  • Example: "You should take your doctor's advice."
  • Example: "Abortion should remain legal."
  • Should means, "There is an overriding reason to..." In the first example, the person is recommending that given all possible choices, there is a reason which is so strong and so compelling, that all other options must be abandoned in favor of following the doctor's advice.
  • Related term: Normative
    • Normative claims are a subset of prescriptive claims which deal with values and morality. The second example, "Abortion should remain legal" is a normative claim.
    • Non-normative prescriptive claims usually follow the following format:
    • If____________, then_____________,
    • as in, "If you want to see a good play, then you should go to the one that is downtown this week.
    • Notice that if you don't go, you haven't done something evil.
    • Frequently normative claims don't contain "should," but rather use a value word, like "wrong" or "good." For instance, "It is wrong to rob banks." Translated it becomes, "One should never rob a bank."

Quiz Quiz

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