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Someone proof read a document I've been working on and made the following amendment. I would like know which one is correct or sounds better. Please develop your answer.

...such strategies are unable to provide continuous benefits


...such strategies are unable of providing continuous benefits

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I am not asking anyone to proofread for me. It is just an honest punctual question about grammar, I would like to know when to use one or the other properly though. – cevel Feb 29 '12 at 4:58
Well, I suppose. I didn't vote to close, now that I think about it. – user11550 Feb 29 '12 at 5:11
I think this is just too basic. Just Googling "unable to" and "unable of" gives 500M hits compared to 0.4M, which imho is all a non-native speaker needs to know. – FumbleFingers Feb 29 '12 at 14:20
I disagree completely, FF. That's like saying all an engineer needs to know is what previous bridges have looked like; no need for stress analysis and still less for calculus in making new ones. – John Lawler Feb 29 '12 at 16:06
I don't think a Google search is a reliable source. Either way, I appreciate the feedback. This will probably be useful to others as well, as basic as it is. – cevel Mar 1 '12 at 7:12
up vote 6 down vote accepted

It's really very simple.

Able (and unable) can take infinitive complements, so the first one is grammatical. But they can't take gerunds, even with epenthetic prepositions, so the second one is not grammatical.

You may be confusing able with capable (and incapable), which means something similar, and which does take a gerund complement with of:

  • such strategies are capable of providing continuous benefits.

and doesn't take an infinitive:

  • *such strategies are capable to provide continuous benefits.
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This is really informative. Thank you. If I could I'd tick your answer twice. :) – cevel Feb 29 '12 at 6:54

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