The Onliest NP: Non-definite Definites

DPs such as the tallest boy, whose head noun is preceded by a superlative adjective – henceforth, the A-est NPs – and DPs such as the only boy, whose head noun is preceded by only – henceforth, the only NPs – are definite in the morpho-syntactic sense because their determiner is the (and not some indefinite determiner such as a or some). But as is well-known (at least since Higgins 1973), the A-est NPs and the only NPs are sometimes semantically non-definite. The following contrasts illustrate this: unlike the tall boy, the tallest boy need not imply existence of a unique boy who is taller than all the other boys; and unlike the boy, the only boy need not imply existence of a unique boy.