In the preceding chapters the point of departure for language acquisition by the child was described psychologically, and the intuitive knowledge of the (adult) user of language, which is built up by acquiring language, was also partially described linguistically. We now want to present the steps and intermediate stages by means of which development proceeds from the starting point to the end (which the linguist rather unclearly calls linguistic competence) and to discuss the theoretical explanation for this progress from the infant without language to the child who is capable of using his language.