Chapter Two, Tutorial 4
Deductive Concepts

 

Remember how we defined valid? Think about it for a moment: an argument is valid if and only if what? (Pick one.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Remember that we defined logical equivalence or sameness of meaning in terms of impossibility. Two sentences are logically equivalent iff what?

  1. it is impossible for each sentence to be false.
  2. it is impossible for one sentence to be true while the other is false.
  3. it is impossible for one sentence of the pair to be false.

Hint: We've defined this one