The ability to learn, understand, explain,
imitate and solve problems.
This ability, or these abilities, that
are much involved in language and mathematics, are the reason the human animal
is more powerful than other animals.
There is good reason to believe that there is such a thing as general
intelligence, in as much as truly intelligent men and women tend to be
similar in being good in both languages and mathematics, good speakers, good
and clear writers, with good memories, and are generally fast in learning many
different sorts of things, and there also is good reason to assume that high
intelligence is positively correlated with a high IQ, which is a good
predictor for scholarly success.
But very probably the basis of intelligence is not one singular faculty nor
one that can be well summarized by a single number, like an IQ. Much rather,
intelligence is like a mountain range: Quite a few abilities, that may all be
cooperatively involved in tasks demanding great intellectual effort, but are
distinct or at most overlapping, and are like tops in a mountain range,
together with necessary valleys coming with these tops.
Also, it is an interesting fact that a good general intelligence seems to
be required to be an extreme talent, but that extreme talents in humans tend
to be specific, apart from their being usually combined with general
intelligence: One is outstandingly good in mathematics, or in foreign
languages, or in music, or in sculpturing, or in engineering, or in chess, or
in painting, but rarely or never very good in all or many of the things men
may excel in.
Indeed, while there have been a considerable number of evidently extremely
intelligent men in human history, who are collectively mostly responsible for
the great ideas and works of art in it, their relative number in the human
population has been small, in the order of 1 or less in a million, and hardly
any, except a rare few like Leonardo, has been truly outstanding in
several fields, even though most truly intelligent men tend to do quite well
in distinct fields, if they try.
Finally, it should be mentioned that extra-ordinary ability is no guarantee
for genius, for that also requires originality and individuality and,
it would seem, a capacity for hard work driven by interest added to these.