This paper shows, after Watkins (1967) and Tremblay (1989, 1991), that
the possessive phrase of This is John's does not necessarily include
an elliptical Possessee. This ambiguity is argued to arise from the du
al nature of the possessive marker, which may either be inflectional o
r derivational in Modern English. In the first case, it may be analyse
d as a functional head, as proposed by Abney (1987) and Kayne (1993, 1
994); in the second case, it operates in the lexicon, deriving possess
ive adjectives which exhibit complementary morphological and semantic
properties in adnominal and predicate positions.