 Frank Jackson holds that “If \(A, B\)” has the truth conditions of “\(A \supset B\)”, i.e. “\({\sim}A\) or \(B\)”; but it is part of its meaning that it is governed by a special rule of assertability. “If” is assimilated to words like “but”, “nevertheless” and “even”. “\(A\) but \(B\)” has the same truth conditions as “\(A\) and \(B\)”, yet they differ in meaning: “but” is used to signal a contrast between \(A\) and \(B\). When \(A\) and \(B\) are true and the contrast is lacking, “\(A\) but \(B\)” is true but inappropriate. Likewise, “Even John can understand this proof” is true when John can understand this proof, but inappropriate when John is a world-class logician. 