Logic / Unit 3 Logic 086 short lesson, about 20 seconds
Contraposition
Captions available
The idea
Contraposition swaps the terms and replaces both with complements. Valid for A and O only.
In practice
"All S are P" becomes "All non-P are non-S."
Where people slip
Conversion works for E and I; contraposition for A and O. Mixing up which operation serves which forms is this unit's signature error.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
Unlocks
Something wrong in this lesson? Flag it · Sources for Logic