Logic / Unit 3 Logic 068 short lesson, about 20 seconds
The Four Standard Forms
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The idea
Every categorical statement reduces to one of four forms: A (All S are P), E (No S are P), I (Some S are P), O (Some S are not P).
In practice
The letters come from Latin: AffIrmo, nEgO — I affirm, I deny.
Where people slip
Four forms carry the entire system. Everything in this unit is bookkeeping on these.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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