Modal logicWe’ll be discussing a specific version of the ontological argument: the modal ontological argument advanced by Alvin Plantinga in 1974. Plantinga’s modal ontological argument specifically uses the “S5” axiomatic system. The argumentThe modal ontological argument takes two premises. The modal ontological argument may be logically valid, but it depends on the premises sounding reasonable-ish. My objections to the modal ontological argument are more or less the same objections that apply to more rhetorical forms of the ontological arguments, the kind that never bother with formal logic.