Peirce and the Unity of the Proposition

The paper addresses the issue of propositional unity in Peirce's logic: what distinguishes a proposition from a mere list of constituents, so that the former is able to say something while the latter is not? I first give a brief survey of Frege's, Russell's, and Wittgenstein's endeavours to cope with the question of the unity of the proposition. I then proceed to analyze Peirce's solution thereof. Like Frege, Peirce developed a chemistry of concepts capable of avoiding the difficulties raised by the unity problem. He subsequently adopted a version of Russell's Principle of Acquaintance and claimed that that which gives a proposition its unity is a peculiar relation that he called "continuous predicate." Finally, I attempt to illustrate what Peirce would have replied to Wittgenstein's claim that logical form is ineffable.