Intelligence, I would think, is how well you can respond to certain situations in a logical manner. Eg., you're house catches on fire and you call 911, get kids, stay low, and evacuate immediately as opposed to running around screaming your head off. I guess it's a compilation of how well you understand things that are explained to you, as well as logical thinking/reasoning. Hard to put a finger on it.
And I think this belongs in the Opinions forum.
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"Abilities" is kind of misleading. You could be Stephen Hawking, one who has very limited abilities, but is an astrophysicist.