In Subanon, an underdescribed Philippine language of Mindanao Island, the prefix mo- appears multifunctional, much like its cognate in other languages. Predicates bearing the prefix variously denote accidental action, ability, acts of perception, statives, unaccusatives, locomotion, or properties. By establishing the paradigms in which the mo- prefix appears, I show that these are not disparate functions of this prefix and its paradigmatically related counterparts, but rather that this morphology, which I call "non-volitional," functions consistently to cancel out any entailment of volition by the most agent-like argument of the predicate. I further show that the non-volitional paradigm is paradigmatically related to a volitional paradigm, and I establish that other uses of mo- are either idiosyncratic, in the case of predicates denoting locomotion, or belong to a separate adjectival paradigm, for predicates denoting properties. This analysis highlights problems that can arise from using multiple, potentially conflicting criteria to define a paradigm, and in the case of Subanon, I resolve such conflicts by making reference to argument structure.