My friend is trying to tell me that the use of "to" in the sentence "we may see the price to rise" (meaning "we expect the price to rise" or "we may see the price rise") is correct. I'm fairly certain this is wrong, but I cannot think of a way to definitively explain why. Can anyone help me out here?
The to-infinitive is often used after an object to express a function that the object serves for the subject, as in:
I have a dog to protect me. (The object's function is to protect the subject)
to express a necessary action that the subject needs from the object:
I need you to finish the report by Friday. (The subject needs the object to finish the report by Friday)
or to express the purpose of a subject's action:
Every night, I give warm milk to him to help him fall asleep. (The purpose of the subject's action is to help the indirect object fall asleep.)
When a subject observed/observes/will observe an object do/doing something, the to-infinitive isn't used.
We saw him hit a home run yesterday.
She hears her neighbours fight every day.
You will feel the medication take effect after an hour.
'To rise' is the infinitive form of the word, whereas 'rise' is a conjugated form. The key here is that you conjugate the first infinitive and then leave the second infinitive alone.
So, it goes something like this:
subject + conjugation
subject + conjugation + direct object
We see the price
subject + conjugation + direct object + conjugation
I see the price rising.
subject + conjugation + direct object + intransitive infinitive
I want the price to rise.
The sentence that you offered as a response:
We expect the price to rise
Invokes the infinitive 'to rise' as an intransitive verb, which does not take a direct object.
I hope that helped!
(To those more knowledgeable than I, please feel free to correct me if I'm mistaken!)