  Coping with ambiguity has recently received a lot of attention in natural
language processing. Most work focuses on the semantic representation of
ambiguous expressions. In this paper we complement this work in two ways.
First, we provide an entailment relation for a language with ambiguous
expressions. Second, we give a sound and complete tableaux calculus for
reasoning with statements involving ambiguous quantification. The calculus
interleaves partial disambiguation steps with steps in a traditional deductive
process, so as to minimize and postpone branching in the proof process, and
thereby increases its efficiency.
