The following text was part of a communication at the Study Day of 28 March 2014 organised by the Centre for the Studies of Foresight Gardes, University Paris 3-Sorbonne New "Poesia — Performance: theoretical, historical and critical issues ", the leaders of which were Olivier Penot-Lacassagne, Gaëlle Théval. They have just published the work resulting from this day (see here: http://www.encd.fr/fr/books/posie-performance/555/) but I had to reduce my contribution to his first time...