 One problem that D-type theories face is that pronouns come with a uniqueness requirement (either as a presupposition or part of the asserted content). But it has been observed that pronouns anaphoric on indefinites do not have a uniqueness requirement; it seems that the truth conditions for such sentences are existential. This observation is nicely captures by Discourse Representation Theory, File Change Semantics, dynamic semantics, and the Context Dependent Quantifier approach (discussed in the next section).  For example, consider (49) again.  This seems true even if many women walked into the contextually salient place at the contextually salient time, and regardless of whether they sat down or not, so long as at least one woman walked in and sat down. Mandelkern &amp; Rothschild (2020) call this phenomenon "definiteness filtering" and Lewis (forthcoming) calls it "the problem of non-uniqueness".  Both of the cited works argue that there is evidence of uniqueness requirements on definites more generally, and the non-uniqueness is specific to the kind of constructions in (49). Mandelkern &amp; Rothschild tentatively propose a D-type theory that employs situation semantics, while Lewis (forthcoming) argues for a D-type theory that takes definite descriptions to be ambiguous between presupposing worldly uniqueness and discourse uniqueness.[29] 