Twenty-seven articles by prominent Indo-Europeanists, Indologists and Iranists have been selected to commemorate the most innovative and consequent exeget of Avesta (the missal of the pre-islamic Paniranian religion, Mazdaeism or Parsism) of our times, Jean Kellens and to inscenery his intellectual pathway and thereby also the present debates around the oldest language and religious history of the common ancestors of Indians and Iranians. The themes Jean Kellens has put into fresh light, intertextuality, stilistics, ideology, textual history and reuse, are especially represented, but always under the light of the mother discipline: grammar.