Im sure this is a well known factoid, but I couldnt remember where I saw it before, and a quick Google search didnt help me find it, so I thought Id just repeat it and see where it may have been said before.
It seems very plausible that the analysis of (1) is (2).
(1) All n Fs are Gs
(2) There are at least n Fs, and there are at most n Fs, and all Fs are Gs
So, if (3) made sense, we would expect that its truth conditions are given by (4).
(3) All two Fs are Gs
(4) There are at least two Fs, and there are at most two Fs, and all Fs are Gs
Surprisingly, in a sense, (3) always sounds quite unnatural. Why might this be? Well, if we accept a Russellian analysis of ‘both’, where ‘Both Fs are Gs’ means (4), then there is a possible explanation of why (3) is odd – it is unnecessarily longwinded. Of course, whether this just so story counts as evidence for the Russellian theory is, at best, questionable, but I thought it was interesting.