Logical exercises involving Santa, Eskimos and Scarlet Fever

(Originally written on November 27, 2006 in Book 9)

Quantificational Logic

No Santas are at the North Pole
Some who live at the North Pole are eskimos
Therefore, eskimos are not Santas

Santa - major term
Eskimos - minor term
At the North Pole - Middle Term

[logical argument and proof not worth typing here]

Some Santas are red.
Some red people have scarlet fever
Therefore, some who have scarlet fever are santas.

[another logical argument, proof and refutation that are not worth typing]

An existential statement is true if it is true for at least one constant. It is false if it is false for all constants.

A universal statement is true if it is true for all constants. It is false if it is true for no constants.