Can we use an infinitive clause with no object in order to specify a purpose?

Question

Even if it is not a common way, it seems that we can use an infinitive clause with no object for a purpose statement.

We talked here before about the accuracy of the question

Who did you find to study with?

and everyone agreed with the idea that "to study with" is an adverbial relative clause there stating a purpose. Then we can see that infinitive clauses don't have to be attached to nouns.

The other example;

She is hard to study with, because, she is really lazy.

Again, "to study with" doesn't need any noun for its own preposition "with".

Let's come to the main point now.

These details make the following sentences grammatically/linguistically correct.

To study with, I found someone who is one of the most successful students at the university.(Why did you find him? To study with.)

According to some people, we have to say:

To study with him, I found someone who is one of the most successful students at the university.

But they don't have any evidence for it.

We don't say:

"She is hard to study with her." or "Who did you find to study with him?"

I believe that in those kinds contexts, we don't need to use a pronoun because using it is more confusing..

What do you think?

If you think that we have to use a pronoun, what is your evidence/reason?

Answer 1

I was not a member of the forum when this issue was originally discussed, so forgive me if anything I say simply repeats what has been said. I would also like to say that I am not a grammar expert, so I am happy to have my conclusions corrected.

Who did you find to study with?

I would have thought that this is a shortened version of:

Who did you find to study with you?

If this is so, then the original sentence only appears not to have a noun or pronoun associated with the infinitive because the second "you" has been elided, although it is still understood to be there.

To study with, I found someone who is one of the most successful students at the university.

This sentence is not grammatical. To retain the intended meaning you could say:

I found someone to study with who is one of the most successful students at the university.

This next sentence is problematic. Taken literally, it mentions three different people, i.e. him, I and someone. Also, taken literally, you are not necessarily studying with the other two people, all you have done is find two people to study with each other.

To study with him, I found someone who is one of the most successful students at the university.

If you change "him" to "me" this sentence would make more sense.

To study with me, I found someone who is one of the most successful students at the university.

But even this sentence could be improved if it was changed to:

I found someone to study with me who is one of the most successful students at the university.

You were correct when you said that we cannot say:

"She is hard to study with her."

but we can say:

She is hard to study with.

which is a sentence that does not require a noun to complement the infinitive. You were also correct in saying that we should say:

"Who did you find to study with him?"

but only because "Who" should be "Whom", although many people would be happy with the sentence without this correction. However, once again this sentence implies that you are finding someone to study with a third person. It makes no sense if it is meant to ask if you have found someone to study with you.