5.2.3.3 Unaccusatives and ergatives
Now let us suppose that this connection between the light verb and its restricted subject, although it is not enough to license accusative Case, is strong enough to license a Case that can be born by indefinites (perhaps partitive). We then have an explanation for why the post-verbal theme is restricted to indefinite DPs. All in all then, the supposition of a (very) light verb in the there construction leads to quite an explanatory account of many of its properties.