Preposition / infinitive

[sonu_gmat]

'...................', an effect that may limit the potential of such medicines for relieving severe pain.

'...................', an effect that may limit the potential of such medicines to relieve severe pain.

Here I'm confused with which one should be used 'for' or 'to'. I read one of MGMAT staff's (Ron) post that says preposition is preferred after noun. I've requested to elaborate that rule but yet to get any reply. My question here is can we apply the same rule here. Is there any other explanation.

[esledge]

This is arguably an idiom, "the potential to do X." For example:
--This prank has the potential to get us in trouble.
--The valedictorian has the potential to go far academically.

However, I also think we can reason against "for" in this case by using grammar rules about modifiers.

In your first sentence, there are two prepositional phrases:
--"of such medicines"
--"for relieving severe pain"

There is some ambiguity about whether both phrases modify "the potential" or each phrase modifies the noun immediately preceding it. In the latter case, "for relieving" just describes what the medicine does, rather than the potential the medicine has.

[sonu_gmat]

Thanks for your reply.

I'm really having hard time to eliminate answer choices having for/to. In the following example (fully rephrased) I chose the first one thinking use of 'to' would be better. I do not think 'they' in the first is ambiguous since it is logically referring to humans. But the second one is given as OA. I understand that second one is more consize. Can you please explain in detail how to deal with such problems.

Researchers claim that the new data will provide clues to determine why humans left the forests in Africa and when they did.

Researchers claim that the new data will provide clues for determining why and when humans left the forests in Africa .

[StaceyKoprince]

I agree that the pronoun "they" logically refers to the humans... but we can't check just logic when dealing with pronouns. We also have to check structure.

Researchers claim that data will provide clues to determine X and Y
X = why humans left the forests in Africa
Y = when they did

There are two problems here. "They" could also refer structurally to "Researchers" b/c Researchers are the subject of the main clause and "they" is a subject pronoun. Even though you know that it should refer to humans from a logical perspective, logic isn't enough. It also has to match structurally.

Second, the whole second subordinate clause (when they did) is ambiguous. When they did what? If you want to say "when they left the forests in Africa" then it should read "when they left," not "when they did."

It also happens that you could construct something correctly using either "provide...to" or "provide...for" so we can't decide purely based on that. We have to look at the rest of the sentence.

Finally, I just want to address something from your first post. When you're looking at the word "to," you aren't always looking at a preposition. In the sentence "I went to the store," to is a preposition. But in the sentence "I like to go to the store," to is a part of the infinitive verb form "to go."

In your first sentence, "to relieve" is an infinitive verb, while "for relieving severe pain" is a prepositional phrase.

I just want to make sure you understand that distinction!

[sonu_gmat]

Thank you so much for your elaborate explanation.

I brought this example because I've seen in several places people eliminated this choice considering 'they' amibiguous as you mentioned in your post. If I had not done the following problem I would have eliminated in the same way because of ambiguity. Please refer the following problem (fully rephrased).

A majority of researchers consider laboratories for testing certain metals unsafe at present but think that they will be or could be made safe in future.

A majority of researchers consider laboratories for testing certain metals unsafe at present but think laboratories would or could be made safe in future.

When I was solving the problem 'they' looked ambiguous to me since structurally it could refer 'researchers' also as you mentioned in your post. So I went with second one. But OA is given as first one since it is more consize and 'they' logically refers to laboratories. So 'they' is not ambiguous at all.

I hope you get my point. I just want to confirm when we can call a pronoun ambiguous in situations such as these.

Thanks for being patient with me on this.

[JonathanSchneider]

The first example uses the "they" only after the verb "think," which connects to "researchers." As the researchers are the ones doing the thinking here, it is likely that the "they" refers to the laboratories. I understand your confusion on this issue; all that I can offer as solace is that issues of pronoun ambiguity are not always reducable to a concrete rule; there is a bit of an art in this process as well. In other words, know when a pronoun is unmistakably ambiguous, but don't go nuts with it.

Moreover, if we wanted to reinsert "laboratories," we would need to say "these laboratories," to make it clear that we are discussing the same laboratories, not different ones.

[RonPurewal]

Moreover, if we wanted to reinsert "laboratories," we would need to say "these laboratories," to make it clear that we are discussing the same laboratories, not different ones.

this is actually the main point.
if you just say "laboratories", then the sentence's meaning is completely wrong; it will be taken to refer to ALL laboratories, not just these particular laboratories.

since this sentence is definitely wrong, and the other is just "possibly ambiguous", the other one wins.

remember, you aren't necessarily selecting the best sentence; much of the time, you're selecting the sentence that is least bad.