Page:Philosophical Review Volume 24.djvu/438

422 of ethics was a task ready-laid to his hand. Locke had given one hint of the precise way in which the mathematical method might be applied. For Locke, "Certainty is but the agreement or disagreement of our ideas, and demonstration nothing but the perception of such agreement by the intervention of other ideas or mediums." Now in mathematics algebra had been of use in supplying these intermediate ideas, and Locke thinks that by applying a kind of algebra in ethics a demonstrably certain system will be produced. Berkeley was not slow to fasten on this hint. "N. B." he says in the Commonplace Book, "to consider well what Locke saith concerning Algebra—that it supplies intermediate ideas. Also to think of a method affording the same use in morals, etc., that this doth in mathematics." Berkeley was keenly interested in algebra (cf. the many references in the Commonplace Book, and the article "De Ludo Algebraico" (1707) in Miscellanea Mathematical). Algebra is itself a department of pure mathematics, for algebra deals with signs abstracted from the things signified. But the algebra of ethics would be a branch of applied mathematics. Thus "Morality may be demonstrated as mixt Mathematics." Berkeley never worked out his algebra of ethics. But he