Deductive Logic

by St. George William Joseph Stock

Denial of Antecedent = Barbara.

Either A is B or C is D.
A is not B.
.'.C is D

is equal to

If A is not B, C is D.
A is not B.
.'. C is D.

is equal to

All cases of A not being B are cases of C being D.
This is a case of A not being B.
.'. This is a case of C being D.

Denial of Consequent = Camestres.

Either A is E or C is D.
C is not D.
.'. A is B.

is equal to

If A is not B, C is D.
C is not D.
.'. A is B.