1.3.5.1 Inflections

We need to distinguish between two groups of auxiliary verb, however. (133a) and (133b) involve aspectual auxiliaries (perfective and progressive respectively). (133c) concerns a modal auxiliary. These two types of auxiliaries differ not only in their semantic content, but also in their syntactic behaviour. For example, while modal auxiliaries are in complementary distribution with one another (there can only ever be one per clause), they are not in complementary distribution with the aspectuals. The aspectual auxiliaries are also not in complementary distribution with each other:

1.3.6 Functionally underspecified categories

We will start with the aspectual auxiliaries. We have pointed out that these auxiliary verbs do not behave like modals as they are not in complementary distribution with them. In fact, aspectual auxiliaries are not in complementary distribution with any I element:

1.3.6 Functionally underspecified categories

This would suggest that they are not categorised in the same way as inflections. They appear to be verbal elements as they inflect for almost the same set of things that verbs do (perfective have inflects for tense (has/had), progressive be inflects for tense (is/was) and perfect aspect (been) and passive be inflects for tense (is/was), perfect aspect (been) and progressive aspect (being)). However, they are clearly not thematic elements in that they play no role in the thematic interpretation of the sentence. Aspectual auxiliaries therefore share properties with verbs and inflections, but they cannot be categorised as either. We can capture this situation if, like verbs and inflections, we categorise aspectuals as [–N, +V] elements, but simply leave the [±F] feature undefined. In common with inflections, aspectual auxiliaries also take only verbal complements and they never precede any other category. However, they may precede either verbs or other aspectual auxiliaries:

1.3.6 Functionally underspecified categories

Given that verbs are categorised as [–F, –N, +V], we cannot claim that this is the category that aspectual auxiliaries subcategorise for as this would exclude them from taking non-thematic verbal complements (i.e. other aspectual auxiliaries). On the other hand, if we claim that they select complements of the category [–N, +V] they would only be able to select for auxiliary complements and not main verbs. The solution to the problem is stating that the category they select as their complement is optionally specified for the [–F] feature, which correctly predicts that they cannot have an inflectional complement.

1.3.6 Functionally underspecified categories

Thus aspectual auxiliaries might have lexical entries such as the following:

5.3 Aspectual Auxiliary Verbs

6.1 The structure of IP

Note that this is a fundamentally different type of structure than the VP that we investigated in the previous chapter. In the VP, apart from the main verb itself, light verbs, both Θ-assigning and aspectual types, select verbal complements and project a verbal phrase. Hence one light verb can take a complement headed by another and a complex VP can be built. Inflections, however, take verbal complements but project an IP. This accounts straightforwardly for why there can only be one inflection per clause as there can only be one IP per clause.

6.2.2 Do-insertion

As we can see, both modal and aspectual auxiliaries can undergo this movement process. The observation of interest to us is what happens when there are more than one auxiliary:

6.2.2 Do-insertion

The reason why (23c) is ungrammatical, then, is that if the aspectual auxiliary moves in front of the subject, it has to move over the modal. Whereas if the modal moves, it crosses over no other head. Now consider the case of verb movement in the presence of not:

6.2.2 Do-insertion

Note that the presence of the negative will not affect the use of aspectual auxiliaries as these are inserted into the inflection position rather than moving to it:

6.2.3 Tense and Agreement

A further problem with the analysis in (36) is the explanation of why the verb cannot move to the I position. We have seen that verbs are perfectly capable of moving, so why this is not possible to the inflection position is quite mysterious. Some, who accepted the ‘I-lowering’ (affix lowering) analysis, have suggested that the verb cannot escape the VP because of its Θ-assigning properties, pointing to the fact that aspectual auxiliaries and copular be, which do not assign Θ-roles, can appear in I (Pollock 1989).

7.3.3 Inversion

Looking at inverted auxiliaries, we see that they all have one thing in common: they are all finite. An inverted auxiliary may be a modal, which is inherently finite, or an aspectual auxiliary which bears tense and we never get a non-finite form of the auxiliary in the inverted position:

7.3.3 Inversion

The case of aspectual auxiliaries is similar to the modals. In the previous chapter we claimed that these auxiliaries are inserted elements that may move from the tense position to the I position when there is null agreement in I. Thus, if they are in I, they can also undergo movement from I to C: