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.