Having separated tense and agreement (=inflection), let us consider their properties separately. Tense is obviously a bound morpheme triggering movement of the verb or insertion of an auxiliary when the verb is unable to move. But what about the null agreement morpheme, is this a bound morpheme or not? If it is, it will need supporting and we would expect verbs and auxiliaries to appear as high as the I node as we do not want to claim that the inflection lowers onto the tense. On the other hand, agreement might be like the modals and be a free morpheme, in which case we would expect nothing to move to I. The data are complex and often depend on other assumptions as to how to interpret them. Basically there appears to be a difference in how verbs and auxiliaries behave. Auxiliaries appear to be able to achieve a higher position than the main verb, indicating that while the verb can move to tense it cannot move to I, whereas auxiliaries can be in I.
As we have seen, adverbs and the negative head can appear in a number of positions within the v/VP, with adverbs being able to adjoin to most phrases above the verb and negation taking most phrases above the verb as its complement:
|(48)||a||will (quickly) have (quickly) been (quickly) being (quickly) hidden|
|b||will (not) have (not) been (not) being (not) cooked|
|(49)||a||for him quickly to have left was a relief|
|b||for him not to have said anything was strange|
However, neither VP adverbs nor negation can precede modals:
|(50)||a||*quickly will leave|
|b||*not will leave|
And neither of them can appear adjoined to a phrase that the verb has moved out from:
|(51)||a||*he will have seen1 quickly [VP the papers t1]|
|b||*he will have seen1 not [VP the papers t1]|
It thus seems that these elements appear anywhere inside the vP as long as they are below the I and above the surface position of the verb.
Now, when there is no modal, an auxiliary inserted to bear tense behaves as though it is in I as no adverb or negation can precede it:
|(52)||a||I have quickly marked the essays||–||*I quickly have marked the essays|
|b||I have not graded the papers||–||*I not have graded the papers|
This supports the assumption that the inflection is a bound morpheme that needs supporting by a verbal element. With main verbs, however, we find that the tensed verb appears below the adverb and the verb cannot support tense in the presence of negation:
|(53)||a||I quickly assessed the students||–||*I assessed quickly the students|
|b||I did not fail his paper||–||*I failed not his paper|
We already have an account for the behaviour of the main verb in the presence of the negative. The negative is a head that blocks the movement of the verb over it. If negation is situated below the I position, then the verb will not be able to move to support the inflection and hence do-support is necessary, as demonstrated in (53b). This will not affect the process of auxiliary insertion however, as this does not involve movement. Yet, an inserted auxiliary bears both tense and agreement and so it seems to be inserted into tense and moved to I, suggesting that the position of the negation is lower than the tensed element, contradicting (49b) where negation is above the non-finite tense. It seems then that negation must be below a finite tense, but above the verb.
The only real problem we face is accounting for the grammaticality of (53a), where the adverb appears in front of the tensed verb. It is this observation which has lead people to the assumption that the inflection must lower to the verb or that the analysis must be more abstract to account for what looks like a downward movement in terms of an upward one.
However, these approaches are based on the assumption that the position of the adverb is rigidly fixed and so if the verb follows the adverb it must be inside the vP. But we have seen that adverbial placement is not so rigid, although it is subject to some restrictions. It would seem to me to be more straightforward to assume that in the case of a finite main verb, the verb does occupy the inflection position and what needs accounting for is the position of the adverb.
Suppose that, like the negative element, the adverb likes to follow the finite tense and precede the verb. However, unlike the negative it is not rigid about this. Specifically, when the verb and the inflection are in one place, it is impossible for the adverb to be between them. Thus a choice must be made: put the adverb above the tense, or put it below the verb. It seems that the restriction on adverbs preceding verbs is the stronger, so the adverb will be adjoined higher than the I position. The position it is actually adjoined to is the I', which we will see is a position where the sentential adverb may appear:
As we mentioned previously, the negative element is not so accommodating and it refuses to give up its place below the finite inflection and above the verb. Thus in this case the verb cannot support the inflection and the dummy auxiliary has to be inserted: