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.