...algebras. He presents the following formulation of the "principle of the permanence of equivalent forms": Whatever form is algebraically equivalent to another when expressed in general symbols, must continue to be equivalent, whatever those symbols denote. Whatever equivalent form is discoverable...

..."Converse Proportion." The other clause, the "Direct Proposition" or "Direct Proportion," was this: "Whatever form is Algebraically equivalent to another,...symbols, must be true, whatever those symbols denote" ( [Peacock 1830] , §132) . Peacock later dropped the Direct Proposition from the statement of the...