In chapter 1, section 5, sentences of the kind «… is ambiguous» were given a normative definition by means of the definiens expression «There is at least one pair of instances of «…» such that the first member of the pair expresses a different meaning from the second». In this normative definition, implicit reference is made to the total class of instances of «…». By (4) and (5) in section 5, hypotheses were formulated according to which instances of an expression «a» belonging to a certain subclass G1 of the total class always express a different meaning from instances of «a» belonging to a second subclass G2. As introduced in section 5, an ambiguity hypothesis asserts the existence of a pair of instances of an expression, the members of which express different meanings. It is introduced as a function of one argument.