If, however, we define intelligence as how well people handle various kinds of thinking, then intelligence most certainly can be learned.
People learn to function more intelligently all the time.
For example, reading is one area where students can learn to funtcion more intelligently. Among the more potent reading strategies were searching backward and forward in texts to clarify obscure points and self-questioning strategies to gauge progress and redirect attention. Then I would read the sentence before it and after it twice. Next I would read that sentence and replace the word with a word that might fit in its place. The value of knowing your way around is not confined to the subject of reading.