What is intelligence?

In his book 'More Games for the Super-Intelligent', James F. Fixx has this to say about intelligence:

... We can agree, too, on at least one other thing: intelligence is well worth having. Intelligence has, to be sure, landed more than a few of its possessors in deep trouble. One thinks, for example, of the student who on a physics examination was asked to describe a method for determining the height of a building by using a barometer. Finding the expected answer obvious and uninteresting, he outraged the educational authorities by giving the two alternate methods: (1) drop the barometer off the building's roof and time the interval until it smashes on the ground; (2) find the owner of the building and say to him, "If you tell me how tall your building is, I will give you a good barometer." ...

There was also a third method proposed: find the owner of the building and say to him, "If you don't tell me how tall your building is, I'll break this barometer over your head."

Haha.