5.4.3 Clausal modifiers
As agent, Harry is the specifier of an agentive light verb and as theme Freda is the specifier of the main verb. The verb will move to support the light verb as usual. We know in this case, the purpose clause can either be controlled by the subject or the object and so it must be able to attach to the structure high enough to allow subject control and low enough to allow object control. Suppose we assume that the purpose clause can adjoin either to the v' or to the V':
5.4.3 Clausal modifiers
The two structures relate to the two possible meanings. When the purpose clause is adjoined to the v', as in (186a), then the agent can control the missing subject, and when it is adjoined to the V', as in (186b), then the theme can control the missing subject. For some reason, when fire is the head of the VP, the purpose clause can only be adjoined to the v' and hence only the agent can be the controller. Hence there will be no ambiguity. Note that the facts as such demonstrate that the purpose clauses must be able to attach within the VP so that objects can act as controllers. If this were never the case, we would only be able to get subject control.
While there may be more or less ‘natural’ readings for these sentences, which are determined by pragmatic considerations, it is possible to think of contexts in which the pronouns could refer to either the subject or the object in each case: perhaps the tailor in (82a) is modelling a suit for the customer and wants to show the customer a certain effect that can best be seen by looking in the mirror, for example. However there are no contexts in which we could make the subject a possible antecedent for PRO in (81a) or the object in (81b) as the referential possibilities in this case are grammatically and not pragmatically determined. We call this property of PRO having to take its reference from one place or another control. Specifically, (81a) involves object control while (81b) involves subject control. It seems that what determines the control properties of PRO is the governing verbs: ask is an object control verb while promise is a subject control verb. Obviously when there is no object, subject control is the only possibility. When there is an object, overwhelmingly verbs tend to be object control and only a very small number of verbs behave like promise and have an object and yet control from the subject.