S.I. Hayakawa's book "Language in Thought and Action" is full of great quotes. Here's just one (fairly big one) that caught my eye.
Indeed, most of the time when we are listening to the noises people make or looking at the black marks on paper that stand for such noises, we are drawing upon the experiences of the nervous systems of others in order to make up what our own nervous systems have missed. Now obviously the more an individual can make use of the nervous systems of others to supplement his own, the easier it is for him to survive. And, of course, the more individuals there are in a group accustomed to co-operating by making helpful noises at each other, the better it is for all — within the limits, naturally, of the group’s talents for organization. Birds and animals congregate with their own kind and make noises when they find food or become alarmed. In fact, gregariousness as an aid to self-defense and survival is forced upon animals as well as upon men by the necessity of uniting nervous systems even more than by the necessity of uniting physical strength. Societies, both animal and human, might almost be regarded as huge co-operative nervous systems.
While animals use only a few limited cries, however, human beings use extremely complicated systems of sputtering, hissing, gurgling, clucking, and cooing noises called language, with which they express and report what goes on in their nervous systems. Language is, in addition to being more complicated, immeasurably more flexible than the animal cries from which it was developed — so flexible indeed that it can be used not only to report the tremendous variety of things that go on in the human nervous system, but to report those reports. That is, when an animal yelps, he may cause a second animal to yelp in imitation or in alarm, but the second yelp is not about the first yelp. But when a man says, “I see a river,” a second man can say, “He says he sees a river” — which is a statement about a statement. About this statement-about-a-statement further statements can be made — and about those, still more. Language, in short, can be about language. This is a fundamental way in which human noise-making systems differ from the cries of animals.