Words are acoustical signs for concepts; concepts, however, are more or less definite image signs for often recurring and associated sensations, for groups of sensations. To understand one another, it is not enough that one use the same words; one also has to use the same words for the same species of inner experiences; in the end one has to have one's experiences in common.
Intelligence is so damn rare and the people who have it often have such a bad time with it that they get bitter or propagandistic and then it's not much use.