Obversion, Conversion, and Contraposition

Question 1

How do you Obvert?

Answer 1

1. Change the quality.
2. Negate the predicate.
   Works for all 4 statement types.
   (Example: All S is P -> No S is not P)

Question 2

What’s Double Negation?

Answer 2

When there are two negating words in a sentence, they cancel eachother out and the statement becomes positive.

Question 3

How do you Convert?

Answer 3

1. Interchange the subject and predicate. Only for E and I statements.
   (Example: No S is P -> No P is S)

Question 4

How do you Contrapose?

Answer 4

1. Obvert.
2. Convert.
3. Obvert again.
   Works for A and O statements.
   (Example: All S is P -> All non-P is non-S)