Logic / Unit 6 Logic 261 short lesson, about 20 seconds
The Four Forms, Upgraded
Captions available
The idea
A: (x)(Sx ⊃ Px). E: (x)(Sx ⊃ ~Px). I: (∃x)(Sx · Px). O: (∃x)(Sx · ~Px).
In practice
Unit 3's four forms, rewritten in the finer notation.
Where people slip
Note the pattern — universals pair with ⊃, existentials with ·. That pairing is a law, and the next-but-one video explains it.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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