Full Idea
The four-dimensional view of objects aids relativity, and the grammar of tenses, but in logic it makes sense of applying a predicate to something that no longer exists, or of quantifying over objects that never coexisted at any one time.
Gist of Idea
Four-d objects helps predication of what no longer exists, and quantification over items from different times
Source
Willard Quine (Philosophy of Logic [1970], Ch.2)
Book Reference
Quine,Willard: 'Philosophy of Logic' [Prentice-Hall 1970], p.31
A Reaction
Since you can predicate of or quantify over hypothetical or fictional objects ('Hamlet is gloomy', 'phlogiston explained fire quite well', 'peace and quiet would be nice') I don't see the necessity for this bold ontological commitment, on these grounds.