 We might call this an objection from Booleanism, both because uniqueness of truth-conditional complementation is characteristic of Boolean approaches to negation, and because similar objections can be motivated by Boolean thoughts about other operations. We might hope to define conjunction so that necessarily, \((A \land B)\) is true iff \(A\) is true and \(B\) is true, and indeed the truth condition for the proposition that \((A \land B)\) is just that both \(A\) and \(B\) are true. But then, with other innocuous assumptions, any two necessarily equivalent sentences will express the same proposition, by a similar chain of reasoning.