Chapter 8

  • Modern Square of Opposition
    1. Made of A E I O statements.
      • A: All S are P
      • E: No S are P
      • I: Some S are P
      • O: Some S are not P
    2. Contradictories are the only consistent relationship.

  • Existential Import
    1. If a statement has existential import, then its referents must exist in order for the statement to be true.
    2. A & E statements do not have existential import.
    3. I & O statements do have existential import.

  • Immediate Inference - Transformation & Equivalence
    1. You can transform A E I O statements in various ways.
    2. There is a table that tells you whether a statement is equivalent to its converse, obverse, or contrapositive.
    3. Kelley calls this Immediate Inference, since the truth of a statement allows you to immediately infer the truth of equivalent statements.

  • Distribution
    1. We say that a term is distributed if the statement refers to all the members of that group in some way.
    2. There is a simple table you can use for distribution.
    3. You must know which terms are distributed in order to apply the Rules of Validity.

Square | Existential Import | Immediate Inference | Distribution | Question? | Self-tests | Logic Page 1