The calculus of logic

by George Boole

..)ⁿ =

(

..), represents an intelligible conception,—a group or class defined by a greater or less number of properties and consisting of a greater or less number of parts.

The four categorical propositions upon which the doctrine of ordinary syllogism is founded, are

All Ys are Xs.	A,
No Ys are Xs.	E,
Some Ys are Xs.	I,
Some Ys are not Xs.	O.

We shall consider these with reference to the classes among which relation is expressed.

A. The expression All