Note 509 — Chapter V
Reading edition
Having determined that All X is P and that All x is q, we may by contraposition bring the latter proposition to the form All Q is X, and it may then be found that P and Q have some alternants in common. These alternants are the terms which (in Boole’s system) are taken in their whole extent in the equation giving X ; and the solution thus obtained is closely analogous to that given by any equational system of symbolic logic.