Logic / Unit 3 Logic 085 short lesson, about 20 seconds
Obversion
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The idea
Obversion flips the quality and replaces the predicate with its complement. Valid for all four forms.
In practice
"All S are P" becomes "No S are non-P."
Where people slip
The complement is everything outside the class — "non-P," not the everyday opposite. Non-happy isn't sad.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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