This paper provides novel cross-linguistic evidence that disjunction in natural language is not the Boolean join of propositional logic, but is better modeled as alternative-denoting. This evidence comes from the behavior of narrow scope disjunction in Tiwa, a Tibeto-Burman language of India, in unreduced phrasal comparatives. On the traditional Boolean approach, disjunctions of typically individual-denoting elements such as names must be treated as generalized quantifier type, predicting an obligatory wide scope reading from within unreduced phrasal comparatives. This reading is not attested in Tiwa, and the attested narrow scope reading is underivable on the traditional account. It is shown that in contrast an alternative-semantic approach can yield the attested reading. All data presented comes from original fieldwork by the author.