Infinitive of purpose

Lori Habermehl, a colleague here in the English Language Centre at Humber, pointed out to me an exception to the textbook descriptions of the infinitive of purpose. This is the infinitive in "I come to bury Caesar, not to praise him." Learners of English often seem to grasp for a preposition to express this and end up, quite reasonably, with for. A decent paraphrase of Mark Anthony's famous line might be "I've come for Caesar's funeral, not for his martyrdom." Unfortunately, "I've come for burying Caesar, not for praising him" is unidiomatic at best, and it is this type of construction that many ESL grammar books are trying to help students avoid in sections on the infinitive of purpose.

Lori then asked, what about sentences like The uranium could be used for making nuclear weapons. I had occasionally noticed that for + present participle could be used to indicate purpose, but I'd never thought properly about it and so I told her I didn't know. Quickly, though, we came up with the hypothesis that it has to do with licensing complements, and a few corpus queries later, we were pretty sure that we were right. In fact, the only verb we could find that allowed this type of construction was use. 

So it seems that infinitives of purpose are adjuncts, while the for + present participle construction is a licensed complement of use. This can be illustrated by the fact that it's common to move the infinitive to the start of the sentence, but rare for a sentence to start with for + present participle.

• To make changes, go to the edit menu.
• Go to the edit menu to make changes.
• Use the edit menu to make changes.
• ?For making changes, use the edit menu.
• Use a non-stick pan to fry the eggs.
• Use a non-stick pan for frying the eggs.
• To fry your eggs, use a non-stick pan.
• ?For frying your eggs, use a non-stick pan.
• Use a non-stick pan to make clean-up easier.
• To make clean-up easier, use a non-stick pan.
• Use a non-stick pan for making clean-up easier.
• ?For making clean-up easier, use a non-stick pan.

(To be honest, I was expecting those ? sentences to sound worse than they do. Maybe I've just talked myself into believing they sound good.)

 I don't think I've ever seen this point addressed by any grammar book.