Curiousity, challenging one's own thinking, seeing / trying to see the perspectives, rather than the ultimates... It's not necessarily even so intelligence that I'm concerned of, I always think people have the capacity and potential to always further develop their understanding and insight, whether to use it is up to them. That's why curiousity & questioning is #1 in my books. Critical thinking. Actually, just thinking.
I suppose I judge originality of thought rather than IQ quotient.
My first thought is that intelligence is multi-dimensional as has been said. After learning about temperaments, I was able to reconcile my judgements about two rather stupid friends I have. Neither went to college- both began working design jobs during and out of highschool. They had no patience for philosophy, they had no quest for meaning or questions of competence. However, they could arrange colors and shapes on a canvas in a way that I could not. They were so deft in youth, and I and others like me could spend a lifetime trying to learn that kind of skill, but may never acquire. The intelligence of sensation is underrated in its abstractness. So, I have reconciled my feelings by saying that intelligence is brain power! So all people have intelligence, and most to a relatively high degree. The question is just where all that mental energy is being directed.
For instance, let's say that we live in a 1984 society. (do we?) The catch is that every single person in this society can either compose brilliant music, mentally compute thermodynamic calculations, recite the dictionary, etc. But none of them realize that they are beneath a bubble of misinformation. That requires more than calculation, the ability of composition, or memorization- it requires intuition. So while all of these people have very high degrees of intelligence, and are capable of far greater than I, none of them pass the bar for truly intelligent people. From now on, I will use the word "smart" rather than "intelligent" at the threshold so as not to be confusing.
A smart person looks down at the world. His body is within it but his focus is not. He realizes contradictions when they are present, understands things as they are, and never compromises data to reflect his bias. He has no faith, or if he does, he admits and fully comprehends the irrationality of it. Competence, as the NT's will say, is a good, natural marker in theory. The only problem with using it as a marker in practice is that competence is not always displayed where it is present.
Some have said "communication" is key. Perhaps. I would argue that ENFP's could "out-communicate" any other type, and by a mile. The last time someone insisted that I was "brilliant" was two days ago. Brilliant is a subjective term, but I believe it is in overstatement if applied to me, because I relate brilliance to genius, and I am no genius. This happens relatively frequently. Because I never speak of complex science (of which I am ignorant) or any other matter that requires high intelligence to comprehend. That is why I am puzzled at assertions that I am smart, though I do not disagree. What puzzles me is how they could have possibly come to that conclusion through such little information. What did I give away? I chalk it up to my communication and lateral thinking. My ideas do not lead to one another in an ordered, logical fashion, but they weave and loop like thread. I am skillful at explaining an idea fully and in detail, and relating that idea to other ideas by pointing out shared facets. This talent of communication may give the illusion that one is smart. Are ENFP's the smartest type, then? That's pretty hard to judge, but my instinct says that if there was an objective measure of intelligence, they would not be. Competence is of course the measure that is most objective - at least that I can think of, and ENFP's are more than competent at what they enjoy, but far less competent at things that matter to others. ENFJ's can also communicate quite well. They will probably connect emtionally with you and then work from there, picking and choosing which ideas to accentuate, but this requires even less intelligence or competence than the ENFP's mending of the explanation of the idea itself in order to make it more easy to grasp. To see a parlor trick as intelligence?
I have much more to say but must cut this short. Sorry if my ideas were so scattered as I bragged of belonging to the most clearly communicative type! I think it works better in person...
Understanding. Understanding is what those geniuses in our mock 1984 lack. Without understanding, you can never be more than a savant, never more than an idiot. What is there to understand? Quite a lot, and asking this question and similar ones is obviously what leads to understanding itself. A person must have a minimum amount of wisdom in order to ask it in the first place. To contemplate the conception of value. The value of importance. The importance of contemplation. To understand the world as it is, and to understand that to understand the world as it is is means to the end of molding the world that could be.
An inscription above the gate to Hell:
"Eternal Love also created me"
Except for FDG and that other guy, whose username is too complicated for me to apply myself to typing. But there's one or two on every forum. n_n (not to demean the subtle humor in their responses, but rather because I was a rabid feminist almost from the time I popped out, and I remain an ass on that subject).