In her Carus lectures, Judith Thomson mentioned that ought seems to be ambiguous between a reading meaning, very roughly, probably and a more normative reading. So, for instance, if Jack is a regular party attender, and Jill has promised to attend this party, (1) is true on the first reading, and (2) on the second. But we have an ambiguity here, as evidenced by the fact that (3) is rather odd.

(1) Jack ought to be dropping by soon.
(2) Jill ought to be dropping by soon.
(3) ??Jack and Jill each ought to be dropping by soon.

I thought this was all terribly interesting, and pretty convincing, but I’m told (by Chris Kane) that it has been discussed a bit in the epistemic deontology literature. (Since I heard the Carus lectures, not read them, I haven’t seen the footnotes where this is probably mentioned. And it might have been mentioned in the lecture too, but I’m not the most attentive of listeners, especially when trying to listen and deal with a mild case of black death or whatever I was suffering from in Cleveland.) So rather than write up all of my thoughts, which included ripping off some of Thomson’s jokes about people falling from the Empire State Building, I just have two quick questions.

First, does anyone have good references on this ambiguity?

Second, does anyone know how widespread this ambiguity is in other languages? Since it appears twice over in English (for should as well as ought) I wouldn’t be surprised if it is widespread. And that would be a neat result I think, since it would undermine a view that is rather widespread in philosophy. The view in question, which is made most explicit in Kripke’s response to Donnellan, is that ambiguity is always a matter of coincidence, so we should assume that English ambiguities will not appear in other languages, especially those not closely related to English. (Actually, Kripke isn’t very clear on the last qualification, so I’m possibly been generous in stating his view here.)