Symbolic Logic

by Lewis Carroll

Univ. “vehicles”; m = comfortable; x = wheelbarrows; y = popular.

xm₀ † m′x₀ ¶ xy₀ [Fig. I.

Conclusion right.

37. No frogs are poetical;
Some ducks are unpoetical.
Some ducks are not frogs.

Univ. “creatures”; m = poetical; x = frogs; y = ducks.

xm₀ † ym′₁

No Conclusion. [Fallacy of Unlike Eliminands with an Entity-Premiss.]

38. No emperors are dentists;
All dentists are dreaded by children.
No emperors are dreaded by children.

Univ. “persons”; m = dentists; x = emperors; y = dreaded by children.

xm₀ † m₁y′₀ ¶ x′y₁ [Fig. III.