I sometimes encounter sentences that use "be able to," which sounds redundant or unnecessary to me. Here is an example:
You have to find data, details, and testimonies that are able to support your arguments.
Personally, I would rewrite the sentence without that phrase since the resulting sentence will be shorter. The resulting sentence--at least from my perspective--means the same thing:
You have to find data, details, and testimonies that support your arguments.
First, am I correct in assuming that they mean the same thing? I realize that the presence of "be able to" puts stress on ability, but for the purposes of limiting what kind of "testimonies" to look for, both sentences are helpful. It's just that one is longer (the one with "be able to").
Is it a matter of redundancy? As far as I understand the sentence, testimonies will either support an argument or not. Hence, saying that a testimony should have the ability to support the argument is already superfluous. If I'm mistaken, please let me know.
When should we not use "be able to" in constructions such as the sentence I presented above?
Is there a set of rules to consult for this kind of issue? Where can I find the rule(s)? I've been scouring books and the net, but I can't find anything about "be able to" and redundancy.
Thanks in advance for the answers!