This article starts from the discussion of some data concerning the acquisition of English as a second language, which suggest that genitival ’s and copular ’s are considered one and the same morpheme by the experimental subjects. The ’s= is Hypothesis is then examined throughout some relevant linguistic literature. The examination of arguments in favour and against it leads to the proposal that ’s is indeed one and the same morpheme whose content is (third) person, in turn a quantificational feature which expresses denotation. In the final part of the paper extensions to plural -s and third person singular -s of lexical verbs are sketched
