(1) a. John ate. b. John ate a rutabaga. (2) a. The popsicles froze. b. Mary froze the popsicles.Up until now, when we've been talking about selection, we've been concentrating mainly on verbs that are obligatorily transitive (like devour), and verbs that are obligatorily intransitive (like rejoice). But we can see in (1-2) that many verbs have what are sometimes called transitivity alternations; they can be either transitive or intransitive.
The transitivity alternations in (1) and (2) are of different types. The one in (1) is comparatively easy to handle; apparently the verb eat always assigns a theta-role to its subject (an Agent theta-role, let's say), and optionally assigns one to an object as well (a Patient theta-role).
In (2), we have a different kind of problem. The verb freeze appears to obligatorily take a Patient, and optionally take an Agent. In (2a), the Patient is the subject, while in (2b), the Patient is the object. So now we have a question: why is the popsicles the subject of (2a) but the object of (2b)?
We can answer part of this question right away. Since Mary is the subject in (2b), there's no way for the popsicles to also be the subject; we wouldn't have any way to draw a tree in which both of these NPs are in the specifier of TP. So the real question is: why is the popsicles the subject of (2a)? This is sort of similar to the question we faced when we were looking at passives: do we want to allow freeze to assign its Patient theta-role in two different structural configurations? Or should we posit a movement operation in (2a), which takes the popsicles out of its rightful place in object position, and moves it to the specifier of TP?
We have lots of good reasons to think that, as with passives, verbs like the one in (2a) are best analyzed by positing movement. In other words, we think that the trees for (2a-b) are the ones in (3) and (4):
(3)
(4)
In this approach, freeze always assigns its Patient theta-role to its complement; it's just that the movement in (3) makes it harder to see this. We call verbs like intransitive freeze, in which the subject begins in object position, unaccusatives. Intransitive verbs which are not unaccusative (like eat in (1b)) are unergative. You may also, especially in older work, see people calling unaccusative verbs "ergative verbs", but we won't do that in this class.
Some of the arguments for this approach to unaccusatives are the same arguments we heard earlier for A-movement in passives. For example, there's an argument from resultatives. We saw before that in clauses with transitive verbs, resultatives can only modify the object, not the subject:
(5) a. John hammered the metal flat. b. John hammered the metal sweaty.And we saw that clauses with passive verbs seem to defy this generalization, allowing resultatives to modify the subject:
(6) The metal was hammered flat.We decided that the best way to handle facts like (6) was to posit a movement operation, moving the metal from object position to subject position. Then the basic generalization about resultatives can be maintained; resultatives modify NPs which begin in object position.
Interestingly, you can also get resultatives with unaccusatives, though not with unergatives:
(7) a. The popsicles froze solid. b. *John ate sick.As with passives, then, we conclude from the resultative data that subjects of unaccusatives (though not subjects of unergatives) begin their lives in object position.
| Optional Reading: This chapter from Beth Levin and Malka Rappaport Hovav's 1995 MIT Press book Unaccusativity discusses resultatives and unaccusatives. |
(to be continued...)