Disjunctive antecedent conditionals

Disjunctive antecedent conditionals (DACs)—conditionals of the form if A or B, C—sometimes seem to entail both of their simplifications (if A, C; if B, C) and sometimes seem not to. I argue that this behavior reveals a genuine ambiguity in DACs. Along the way, I discuss a new observation about the role of focal stress in distinguishing the two interpretations of DACs. I propose a new theory, according to which the surface form of a DAC underdetermines its logical form: on one possible logical form, if A or B, C does entail both of its simplifications, while on the other, it does not.