I must confess that the theoretical importance of the two phases, which  emerged in my research on BE+ING and DO nearly twenty-five years ago, has so to speak taken me completely unawares. I had absolutely not anticipated that I could ever be confronted with a principle of that kind . Frankly , nothing in the linguistic literature I had been exposed to had prepared me to this masterpiece of symmetry and systematicity (perhaps Gustave Guillaume, indirectly ?) . The Principle of Cyclicity I stumbled on while writing " Caroline Grammairienne en Herbe " (1993-95) was the natural and logical consequence of the regularities I had dug up. This principle , which plays a decisive role in the organisation of grammars, cannot not play  an important part in the acquisition of the mother-tongue by  young children . Steven Pinker's statement that every three-year child is a grammatical genius (" The Language Instinct ", Penguin 1995, p.19) ceases to be a simple statement of fact : now we begin to understand the actual task of the child exposed to the language of his entourage. For decades linguists have been repeating that language is a system without being able to precise what sort of system it was. Similarly Chomsky's notion of " Universal Grammar " , interesting though it is, is so far nothing but an empty shell.