We hope that the above has given a hint of the way powerful structures can come into being on the basis of a collection of basic constructive mechanisms. The answer to the question of how many there are in the collection would seem to be `as many as are needed to do an efficient job'. The discipline of artificial intelligence has shown that many different processes are required to do even the simplest operations effectively. But these processes do not all have to be innate if they can be constructed, and if they can select themselves out of the many possible constructions by virtue of their effectiveness in the life of the advancing child.