Full Idea
A definite description may also be used non-referentially, even as it occurs in one and the same sentence.
Clarification
A definite description has the form 'the so-and-so'
Gist of Idea
A definite description can have a non-referential use
Source
Keith Donnellan (Reference and Definite Descriptions [1966], §I)
Book Reference
'Naming, Necessity, and Natural Kinds', ed/tr. Schwartz,Stephen P. [Cornell 1979], p.43
A Reaction
Donnellan says we have to know about the particular occasion on which the description is used, as in itself it will not achieve reference. "Will the last person out switch off the lights" achieves its reference at the end of each day.