Logic / Unit 6 Logic 267 short lesson, about 20 seconds
Universal Instantiation
Captions available
The idea
From (x)Fx, derive Fa — or Fy — for any constant or variable. What's true of everything is true of each thing.
In practice
(x)(Hx ⊃ Mx), so Hs ⊃ Ms. Socrates inherits the rule.
Where people slip
UI is generous — instantiate to anything. The other three quantifier rules are not so relaxed.
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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