J.S. Mill believed that the meanings of singular terms were their denotations. Denotations are usually seen as objects of some description. Therefore a proposition, if it had a term whose meaning was its denotation, would literally(?) have an object within it.
The Individuation of Objects
In terms of the modes of presentation of an object, it can also be said that a criterion of identity must come along with a “principle of unity”. In addition, an object must have some kind of temporal longevity if it's to be deemed an object in the first place.