The transformative idea in Peirce’s case of the French interpreter is not the convertibility of term logic, propositional logic, and monadic predicate logic — a commonplace of logic from the time of Aristotle, if not in those words, obscured only by the false subtleties of the Frege-Russell tradition, though even Quine was woke enough in time to write a nice essay on it — but rather the transformation from interpreter models to interpretant models of semiosis. The latter models are what Peirce and all in his train require for constructing abstract formal theories neutral on psychologism, materialism, biologism, and various other all too stolid -isms.
There’s more discussion of Peirce’s passage to the interpretant at the following locations.
- Peirce, C.S. (1902), “Parts of Carnegie Application” (L 75), in Carolyn Eisele (ed., 1976), The New Elements of Mathematics by Charles S. Peirce, vol. 4, 13–73. Online.
- Peirce, C.S., Writings of Charles S. Peirce : A Chronological Edition, Peirce Edition Project (eds.), Indiana University Press, Bloomington and Indianapolis, IN, 1981–. Cited as (CE volume, page).