auxiliary verb. b. Sam yearns to go. - yearns is a subject control verb. a. Jim has to do it. - has to is a modal auxiliary verb. b. Jim refuses to do it. - refuses is a subject control verb. a. Jill would lie and cheat. - would is a modal auxiliary. b. Jill attempted to lie and cheat. - attempted is a subject control verb. The a-sentences contain auxiliary verbs that do not select the subject argument. What this means is that the embedded verbs go, do, and lie and cheat are responsible for semantically selecting the subject argument. The point is that while control verbs may have the same outward appearance as auxiliary verbs, the two verb types are quite different. Non-obligatory or optional control Control verbs (such as promise, stop, try, ask, tell, force, yearn, refuse, attempt) obligatorily induce a control construction. That is, when control verbs appear, they inherently determine which of their arguments controls the embedded predicate. Control is hence obligatorily present with these verbs. In contrast, the arguments of many verbs can be controlled even when a superordinate control verb is absent, e.g. He left, singing all the way. - Non-obligatory control of the present participle singing Understanding nothing, the class protested. - Non-obligatory control of the present participle understanding Holding his breath too long, Fred passed out. - Non-obligatory control of the present participle holding In one sense, control is obligatory in these sentences because the arguments of the present participles singing, understanding, and holding are clearly controlled by the matrix subjects. In another sense, however, control is non-obligatory (or optional) because there is no control predicate present that necessitates that control occur. General contextual factors are determining which expression is understood as the controller. The controller is the subject in these sentences because the subject establishes point of view. Arbitrary control Arbitrary control occurs when the controller is understood to be anybody in general, e.g. Reading the Dead Sea Scrolls is fun. - Arbitrary control of the gerund reading. Seeing is believing. - Arbitrary control of the gerunds seeing and believing Having to do something repeatedly is boring. - Arbitrary control of the gerund having The understood subject of the gerunds in these sentence is non-discriminate; any generic person will do. In such cases, control is said to be "arbitrary". Any time the understood subject of a given predicate is not