Many people believe, like Sherlock Holmes, that the human brain has a finite capacity. Recent work on memory, however, suggests that such a view is mistaken. A healthy person's memory is indefinitely extendable provided that the information it contains is well organized, and not just a jumbled heap of random items.

Every language contains a finite number of patterns, as we have already pointed out. It is these patterns which enable humans to remember any language so apparently effortlessly. If the patterns were to break down, a person's brain would become overloaded with fragmented pieces of information. Efficient communication would become difficult, if not impossible.

As this chapter will show, language has a remarkable instinct for self-preservation. It contains inbuilt self-regulating devices which restore broken patterns and prevent disintegration. More accurately, of course, it is the speakers of the language who perform these adjustments in response to some innate need to structure the information they have to remember.

In a sense, language can be regarded as a garden, and its speakers as gardeners who keep the garden in a good state. How do they do this?