Control Theory

In generative syntax, control theory is a would-be theory that accounts for the referential properties of PRO.

Examples
The fact that John is the understood subject of to do the dishes in (i) but not in (ii) (Susan is the understood subject of to do the dishes in (ii)) is to be accounted for by control theory.

(i) Johni promised Susanj [PROi to do the dishes]

(ii) Johni ordered Susanj [PROj to do the dishes]

Comments
Sometimes the term 'control theory' is used for whatever explains those aspects of the behavior of PRO which are not captured by other theories (such as binding theory or the theory of predication).

Link
Utrecht Lexicon of Linguistics