While I disagree with the idea that IQ isn’t a reasonable measure of intelligence, I very much agree with the distinction between intelligence capacity and intelligence utilization. From New Scientist:
The problem with IQ tests is that while they are effective at assessing our deliberative skills, which involve reason and the use of working memory, they are unable to assess our inclination to use them when the situation demands. This is a crucial distinction: as Daniel Kahneman at Princeton University puts it, intelligence is about brain power whereas rational thinking is about control. “Some people who are intellectually able do not bother to engage very much in analytical thinking and are inclined to rely on their intuitions,” explains Evans. “Other people will check out their gut feeling and reason it through and make sure they have a justification for what they’re doing.”
The analogy I prefer is firepower. IQ is intellectual firepower. Some have .22 caliber popguns, some have 152mm howitzers. But a .22 to the forehead is far more lethal than a 152mm artillery shell that falls miles wide of the target. This is why I occasionally refer to “functional idiots”. These are people with the intellectual capacity to function in an intelligent manner who for various reasons don’t actually use that capacity and so end up with conclusions that are identical to those reached by people without any such capacity.
When people are doing the same stupid thing over and over again, when they are trusting the word of some scientist or priest rather than critically examining the reliability of that word, when they are operating on the basis of information instilled in childhood about which they have never actually thought or on pure emotion, it does not matter how intelligent they are, because they are obviously not making use of that intelligence.
One of the greatest challenges that intelligent people face is learning to distinguish between when they are using their intelligence and when they are not actually making use of it. The action of an intelligent person behaving thoughtlessly is no more likely to be intelligent than the action of an unintelligent person, and in fact, if the action of the intelligent person is not guided by the wisdom of the stored societal knowledge known as tradition, it is actually very likely to be observably less intelligent and lead to less positive results.
What Chesterton described as “the democracy of the dead” may not always be the optimal path, but it is unlikely that it is the most suboptimal one. As has been demonstrated many times throughout the past, creating a significant disaster worthy of historical note usually requires a truly intelligent person. This is why wisdom is always to be preferred to mere intellectual brilliance.