Different verbs take different types of complements and assign them to various positions. 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 to the complement of V -- the VP1 position. An ergative verb assigns its argument to the external position: VP2. The agent seems to be universally assigned to the external position. There is a theoretical reason for this, but it lies beyond scope of this class. Ergative verbs include: go, walk, run, swim, work, crawl, sleep (all of these verbs must be intransitive to be ergative). Unaccusative verbs assign theme or patient to the internal position; there are a large number of unaccusative verbs: break, crack, melt, cook, thaw, shine, fall, grow *(all of these verbs must be intransitive to be unaccusative). Many of these verbs have a transitive counterpart which are transitive verbs, often called causative verbs:
the window broke (unacc.) -- John broke the window (causative)
the pot cracked (unacc.) -- Mary cracked the pot (causative)
the ice melted (unacc.) -- The sun melted the ice (causative).
Unaccusative verbs assign the theta role theme or patient to their complement--the sister to the head:
Ergative verbs assign the theta role agent, experiencer, or instrument to their
indirect complement, the sister of VP1:
If an unaccusative verb is reformed into a causative verb, the agent is assigned to the external argument:
Note that the sun is an instrument here, since the sun, as far as I know, has no central processing unit.
The evidence differentiating ergative verbs from unaccusative ones is not very strong in English. Ergative verbs cannot take a resultative clause, but some unaccusative ones may:
- The ice melted into water.
- The cake burned to a crisp.
- The ugly duckling grew into a beautiful swan.
The final PPs in each sentence are resultatives--they describe what the subject has turned into.
- *The ugly duckling walked into a beauftiful swan. (i.e. became one).
- *John ran into a prof of syntax (i.e. became one).
Another property that helps to distinguish them is that the argument of a verb of motion (ergative) may remain unraised under certain conditions, but this does not appear to be the case with the argument of an unaccusative verb:
- Here comes Mary, and there goes John.
- On the bench is sitting a poor beggar.
- There is a unicorn in the east garden.
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