Iena's period is a decisive one for the formation of mature hegelian thought: progressive gap with Schelling, first attemps to elaborate a new philosophical system, incessant reorganization of the way logic, nature, spirit have to be conceived; the book, which includes a translation of important papers from Klaus Düsing, Ludwig Siep and Franco Chiereghin, means to investigate theses transformations in order to fill a deficiency in the field of Hegelian french-speaking studies