The calculus of logic

by George Boole

s are

s. It is always necessary that one term of the conclusion should be interpretable by means of the equations of the premises. In the above case both are so.

Ex. 3.	All Xs are Ys,	x = vy,
	No Zs are Ys,	z = v'(1 - y).

Instead of directly eliminating

let either equation be transformed by solution as in (19). The first gives