  How can we avoid these difficulties? Roeper (1983), Lønning (1987) and Higginbotham (1994) propose that the solution lies in defining predication and negation in a certain way within a Boolean  algebra.[12] They consider only cases where predicates (mass nouns included) are “homogeneous”, like above. Following ter Meulen (1981), a predicate is said to be homogeneous if it applies both cumulatively and distributively. Predicates like gold and in the safe may indeed seem to apply distributively and cumulatively, if we stay at the macroscopic level for gold. In this approach, mass nouns and predicates denote elements in a certain Boolean algebra, (B,≤,∨,∧0,1). ≤ is the order (or parthood) relation. ∨ is the join (or sum) operation. ∧ is the meet (or intersection) operation. 0 is the smallest element. 1 is the largest element. As in any Boolean algebra, every element x has a Boolean complement, noted −x (cf. Monk 2018).