Logic / Unit 6 Logic 268 short lesson, about 20 seconds
Universal Generalization
Captions available
The idea
From Fy, where y is arbitrary, derive (x)Fx. Restriction: y must not have been introduced by EI, nor be free in an undischarged assumption.
In practice
Proved for an arbitrary y, with no smuggled specifics — then proved for all.
Where people slip
"Arbitrary" is load-bearing. Generalizing from a name is how one proves that everything is Socrates.
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