Solutions to Chapter 29 Ambiguity

Practice exercises

A. Each of the following sentences is ambiguous. Provide a symbolization key for each, and symbolize all readings.

  1. 1.
    ​

    No one likes a quitter.

    domain:

    people

    Q⁡(x):

    blank x is a quitter

    L⁡(x,y):

    blank x likes blank y

  2. ∀x⁢(Q⁡(x)→∀y⁢¬L⁡(y,x)) (all quitters are disliked by everyone)
    ∃x⁢(Q⁡(x)∧∀y⁢¬L⁡(y,x)) (A specific quitter is disliked by everyone)

  3. 2.
    ​

    CSI found only red hair at the scene.

    domain:

    items of evidence

    R⁡(x):

    blank x is red

    H⁡(x):

    blank x is hair

    F⁡(x,y):

    blank x found blank y (at the scene)

    c:

    CSI

  4. ∀x⁢(F⁡(c,x)→(R⁡(x)∧H⁡(x))) (only hair was found, and it’s all red)
    ∀x⁢((F⁡(c,x)∧H⁡(x))→R⁡(x)) (only red hair was found, but possibly other things that aren’t hair)

  5. 3.
    ​

    Smith’s murderer hasn’t been arrested.

    domain:

    people

    A⁡(x):

    blank x has been arrested

    M⁡(x,y):

    blank x murdered blank y

    m:

    Smith

  6. ∃x(∀y(M(y,m)↔y=x)∧¬A(x)) (Smith’s murderer has: not been arrested)
    ¬∃x(∀y(M(y,m)↔y=x)∧A(x)) (It’s not the case that Smith’s murderer has been arrested; in fact there may not be a “Smith’s murderer”.)