3.2.2.2 S-structure and Case Theory

So far we have looked at some of the principles governing the distribution of arguments at D-structure. In order to understand movement we must now consider some of the principles that apply at S-structure which determine the distribution of arguments at this level.

In chapter 2 we mentioned the grammatical notion of Case, pointing out that certain pronouns in English have different Case forms. Nominative pronouns include he, she, I and we while accusative pronouns are him, her, me and us. What determines which form the pronoun appears in is apparently its S-structure position. If a pronoun is the subject of a finite clause it will be nominative, anywhere else it is accusative (we ignore the possessor position inside the DP which is associated with genitive Case: his, her, my and our):

In (84a) the clause is finite as tense is marked on the auxiliary verb. The subject he is in the nominative form, not the accusative him. However, the object of the verb help, her, is in the accusative not the nominative she. In (84b), while the main clause is finite and has a nominative subject, I, the embedded clause is non-finite. This clause has an accusative subject him. The object of the preposition in this clause is also accusative, us.

Now consider the following example:

The pronoun is in the subject of a finite clause and so naturally is in the nominative. However, as this clause is passive, the pronoun originates from the object position at D-structure. But this fact does not seem to have any bearing on the case of the pronoun: the pronoun is nominative not accusative as a non-moved object would be. Clearly, then, it is the position that a pronoun sits in at S-structure that determines its case. We might claim therefore that there are positions which are Case positions, specifically nominative positions and accusative positions, and there are positions which are not Case positions.

But if there are nominative and accusative case positions, what are we to say about the non-pronominal DPs that sit in these positions as no other DP demonstrates morphological Case distinctions? There are two things that we might say. One is that Case positions are only Case positions when occupied by a pronominal DP. This would be rather difficult to arrange however, as it appears that apart from the fact that Cases are only visible on pronominals, what defines Case positions is fairly general: the subject of a finite clause is nominative, the object position of a verb or preposition is accusative and the subject position of a non-finite clause is accusative. It is not clear how to include the presence of the pronominal into the definition of a case position.

The alternative is to claim that there are general case positions that are occupied by any DP, but only some DPs show any morphological reflex of this. Obviously this is the more general and simplest position and hence it is preferable unless there can be demonstrated to be advantages of accepting that case positions are only defined in the presence of a pronoun.

One reason to believe that case positions are generally defined but just morphologically distinguished on certain elements is the fact that case is not distinguished on all English pronouns. For example there is no distinction between nominative and accusative for the pronoun it:

The third person singular masculine pronoun demonstrates a Case distinction between subject and object position in (86), but not the pronoun it. It would be extremely difficult to account for why Case positions are only defined in the presence of pronouns, except for it and would be much better to say that the Case position is defined in the presence of it but this pronoun does not realise the distinction overtly. In other words, it is the nominative form of this pronoun and it is the accusative form. But once we have accepted this as a possibility it is reasonable to accept it for all other nominal elements as well.

One way to view this situation is to separate two notions of Case. One notion of Case, relating to the traditional view, is that Case has to do with the form a nominal element takes dependent on its position or, in some languages, its function in a sentence. We can call this phenomenon Morphological case. The other view of Case is that this is something a DP gets simply by occupying a certain structural position, whether or not it is realised overtly. We call this Abstract Case, or just Case (spelled with a capital). From this perspective then, any DP that occupies the subject position of a finite clause has nominative Case irrespective of whether that DP looks different from what it would if it were sitting in an object position and bearing accusative Case.

One piece of support for this distinction comes from observations such as the following:

In (87) we have a series of pronominal subjects of non-finite clauses. In the one grammatical case the subject is accusative, demonstrating that this is an accusative position. The ungrammaticality of the nominative pronoun in (87b) is therefore understandable. That (87c) should be ungrammatical is interesting as here we have an accusative pronoun. In this case the complementiser for is absent, indicating that this element is in some way responsible for the accusative case in (87a) in which it is present. This is understandable as this complementiser is similar to a preposition, and in fact is often called the prepositional complementiser, and as we know, the complement of prepositions is in the accusative. To account for this let us assume that Case is rather like Θ-roles and is assigned by certain elements to certain positions. The prepositional complementiser therefore assigns accusative Case to the subject of the non-finite clause that it introduces:

Although this might explain why the subject has accusative Case in (87a) and cannot have nominative Case in (87b), by itself it does not account for why (87c) and (d) are ungrammatical. To understand what is going on here we must attend more closely to the facts. Firstly the element that we have assumed to assign accusative Case to this position is absent and so we might assume that no accusative Case is assigned in these circumstances. Presumably whatever it is that assigns nominative Case is not present in a non-finite clause. Therefore in this situation it seems that neither accusative nor nominative case are assigned to the subject position.

But why would any of this mean that the sentence should be ungrammatical? Only with an extra assumption can we account for this properly: the pronoun subject needs a Case. One might think that this is fairly obvious as there is no Case neutral form of the pronoun: what form would it take if it occupied a Caseless position? However, the following observations seriously question the assumption that the ungrammaticalities in (87) have anything to do with Morphological case:

What we see here is that even a nominal element that does not display morphological case distinctions cannot occupy a position to which no Case is assigned. Thus the requirement that a nominal element have Case is nothing to do with the impossibility of the choice of morphological form when no Case is assigned. Instead, it appears to be a general requirement that all DPs must occupy a Case position. We call this requirement the Case Filter:

The fact that the Case Filter applies to all DPs and not just those that demonstrate morphological case is strong evidence in favour of the assumption of Abstract Case.

Let us review what we have said so far. We started with the observation that the position that a DP occupies at S-structure determines its Case. We then claimed that Case is something applicable to all DPs and finally we proposed a general condition to the effect that all DPs must receive Case. But putting all this together it is obvious that the Case Filter can only operate at S-structure as, as we have seen, D-structure positions are in general irrelevant for determining the Case of an element. Consider the possibility that all the grammatical principles involved with Case and its assignment are bundled together in a single Case theory, paralleling Theta Theory discussed above. Case theory then applies to S-structure:

While Theta theory accounts for the distribution of arguments at D-structure, it is the principles of Case theory that account for the distribution of DP arguments at S-structure.

We are now in a position to be able to understand at least certain aspects of movement. Suppose that the principles of Theta theory determine that a DP argument must sit in position X. Suppose further that position X is not a position to which Case is assigned. If the DP remains in this position at S-structure, then the Case filter will be violated and the structure will be deemed ungrammatical. If on the other hand the DP can move to a position to which Case is assigned, then the movement will enable the Case Filter to be satisfied and the structure to be grammatical. This kind of movement might be said to be Case motivated and as we shall see, there are quite a few movements which follow this pattern. This is not the only motivation for movements, however, though we will not go into others at this point. The purpose of this section has been mainly to demonstrate how the interaction of grammatical principles applying at D-structure and S-structure can provide us with an understanding of movement phenomena.