Deductive Logic

by St. George William Joseph Stock

FIGURE II.

§ 653.

A is B. A is not B.
C is not B. C is B.
.'. C is not A. .'. C is not A.

We establish the distinction between C and A by showing that A has an attribute which C is devoid of, or is devoid of an attribute which C has.

All fishes are cold-blooded.
A whale is not cold-blooded.
.'. A whale is not a fish.

No fishes give milk.
A whale gives milk.
.'. A whale is not a fish.