In many Italian comparative sentences the negative element 'non' appears, as in 'Maria è più intelligente di quanto non sia Carlo' as opposed to 'Maria è più intelligente di quanto è Carlo' (both meaning 'M is more intelligent than C). If 'non' is present, the speaker is said to presuppose that his statement contradicts someone else's belief or his own previously held belief. N. and N. argue that the data can be accounted for in terms of a presupposition-free model of syntax.