Deductive Logic

by St. George William Joseph Stock

FIGURE IV.

§ 655.

All A is B, No A is B.
All B is C. All B is C.
.'. Some C is A .'.Some C is not A.

We show here that A is or is not a species of C by showing that A falls, or does not fall, under the class B, which itself falls under C. Thus—

All whales are mammals.
All mammals are warm-blooded.
.'. Some warm-blooded animals are whales.
No whales are fishes.
All fishes are cold-blooded.
.'. Some cold-blooded animals are not whales.