Previous research has documented that children count spatiotemporally-distinct partial objects as if they were whole objects. This behavior extends beyond counting to inclusion of partial objects in assessment and comparisons of quantities. Multiple accounts of this performance have been proposed: children and adults differ qualitatively in their conceptual representations, children lack the processing skills to immediately individuate entities in a given domain, or children cannot readily access relevant linguistic alternatives for the target count noun. We advance a new account, appealing to theoretical proposals about underspecification in nominal semantics and the role of the discourse context. Our results demonstrate that there are limits to which children allow partial objects to serve as wholes, and that under certain conditions, adult performance resembles that of children by allowing in partial objects. We propose that children's behavior is in fact licensed by the inherent context dependence of count nouns.