In this thesis I will justify the use of negative forms of evidence as a permissible means of analysing grammatical constructions. I do this by presenting a test case, a grammatical construction that is not entirely understood, and attempting to understand and explain further aspects of it by appealing to negative forms of evidence. The constructions that form the object of this investigation are complex predicates in the Wagiman language. It will be necessary first, to provide a detailed explanation of Wagiman complex predicates; the elements that comprise them, the way those elements combine and the limitations that hold on them. Following that, negative evidence of the combinations that are possible and combinations that are impossible will provide the means by which to identify the constraints that limit complex predicates.