Two that we will consider here are ergative and unaccusative verbs. The basic one each assign a single argument. Given the binary V -- VP1 -- VP2 hypothesis, an unaccusative verb assigns its argument ...

If we are told that we 'must' do something, like complete homework, the modal verb 'must' indicates a high level of modality. There is no argument. The homework has to be done. But if we are told ...