The rationale clause infinitive is a modifier of the verb which expresses an agent's intention in acting as they do. The rationale clause is related to the matrix in two important ways: the null subject of the infinitive (PRO) is usually coreferential with a phrase in the matrix (control), and the intention it expresses is usually assigned to a phrase in the matrix (predication). Given that the controller and argument of the rationale clause are usually clausemates of the infinitive itself, the strongest hypothesis is that both control and predication are strictly local. However, there has been much debate in the literature concerning the viability of such a locality constraint. In this article, I argue in favour of a locality-based account of control and predication in the rationale clause, comparing it with a discourse-semantic constraint approach and a logophoricity constraint approach. Data from two related modifier infinitives (the purpose clause and the telic clause) will be used to sharpen the discussion.