# Government and Binding Theory/VP-Shell Hypothesis

So far, in the analysis of X-bar theory, we have only looked at verbs with one complements. However, a problem arises: What about two complements? Here are some examples:
(1a) I gave Mary a pen. (1b) He got a warning from the teacher.
In (1), both sentences have two complements. It may be tempting to give them this structure:
However, that violates the Binary Branching Condition. Now, it may again be tempting to try this structure, where the second complement is placed in adjunct position:
Indeed, for some time, these were the standard treatments of double complement constructions in GB theory. But do they work?

## Asymmetries of double objects

Treating complements as adjuncts or VPs as ternary branching structures are not without problems. While ternary branching works somewhat for examples like (1b), both fail at verbs VP + NP + NP constructions like (1a), as we will demonstrate here. However, before we proceed, we need to look at the concept of c-command.

### c-command

* c-command
* α c-commands β iff the node immediately dominating α also dominates β.
In simpler terms, α c-commands β iff β is the sister of α or is dominated by the sister of α.
You can find c-commanded nodes visually by following a simple rule: Go up one then down one or more, and any node you land at will be c-commanded by the node you started at:

### Problem 1: Reflexives and Reciprocals

Reflexive and reciprocal pronouns can only be referentially dependent on expressions that c-command them, as you can see below (we will expand on this many chapters later):
(2a) I$_i$ introduced myself$_i$ (2b) *Myself$_i$ is so proud of me.
(2a) works as I c-commands myself, as you can see. (2b) doesn't work. As nothing c-commands myself, it cannot refer to anything, and the sentence is thus ungrammatical. In double-object constructions, the second object can be referentially dependent on the first, but not vice versa:
(3a) I showed Mary$_i$ herself$_i$ (3b) *I showed herself$_i$ Mary$_i$
This suggests that Mary c-commands herself in (3a).

### Problem 2: Quantifiers

A very similar situation is the quantifier. Refer to the following:
(4a) Every good boy$_i$ does his$_i$ homework. (4b) *His$_i$ homework is done by every good boy$_i$.
(4b) doesn't work. As every good boy does not c-command his, his does not refer to anything. Now look at double-object constructions:
(5a) He gave every student her essay. (5b) *He gave its writer every essay.
Again, analogously, every student should c-command her essay in (5a). Note that (5b), if reformulated as He gave every essay to its writer', the sentence would be grammatical.

### Problem 3: Negative Polarity Items

Yet another similar problem occurs when we use negative polarity items, such as any:
(6a) Nobody knows anything about linguistics there. (6b) *Anybody knows nothing about linguistics there.
As you can guess, double object constructions also show that the first object c-commands the second:
(7a) I gave nobody anything. (7b) *I gave anybody nothing.

### Conclusion

There are other cases where the two objects are not created equal, but this will do for now. We can, with the above data, prove the ternary and adjunct hypothesis false:
* If the adjunct hypothesis were true, the second object would c-command the first object, rather than vice versa, which is the actual situation. The adjunct hypothesis is thus false.
* If the ternary branching hypothesis were true, the two objects should c-command each other, but it is clear that the second object doesn't c-command the first. Thus the ternary branching hypothesis isn't true, either.
This led to a third hypothesis, the VP shell.

## VP-Shell Hypothesis

In light of the evidence above, a new structure for double-object constructions has been introduced, in which the verb originates between the two objects and moves to the front (the structure for VP + NP + NP constructions is actually slightly more complicated than has been shown here, but we're not in a position to reveal the whole story):
With this new construction, we can explain all our problems above. We will give one example, and you can work out the rest on your own:
In gave nobody anything, nobody c-commands anything, so the negative polarity item is grammatical. In gave anybody nothing, anybody is not c-commanded by nothing, so the phrase isn't grammatical.

### Further Evidence: Idioms

The VP-Shell Hypothesis is supported by the fact that in some dative constructions where the PP complement always succeeds the NP complement, the VP and PP form an idiom:
(8a) He takes his girlfriend for granted. (8b) He takes his girlfriend to the cinema.
(8a) and (8b) have the same structure, but different PP complements. The word takes does not mean the same thing in both: take for granted is an idiom in (8a). Under the VP-shell hypothesis, take for granted was originally a single phrase before takes was moved to the front.

## Ergative Verbs

The VP-shell hypothesis has been further developed to account for an interesting phenomenon known as ergative verbs. Refer to the examples below:
(9a) The water evaporated. (9b) He evaporated the water. (9c) He made the water evaporate.
The VP-internal subject hypothesis states that the subject originates from inside the VP, and moves to the IP's subject position. For now, we'll take this for granted, but we'll return to the hypothesis soon. By this hypothesis, (9a) can be written thus:
As for our (9c), the water evaporate is a VP complement of made:
How about (9b)? This is where the abstract verbal element e comes in. (9b) originally assumes the same structure as (9c), with e as the head of the outer VP. The head of the inner VP then moves and attaches to e: