The historiography of French Art nouveau has often, because of the lack of private archives, presented the architect Hector Guimard, a pioneer of this short-lived and singular movement, as a solitary and even misunderstood genius, and set him apart from the literary and philosophical movements of his time. The discovery that he had in his youth to a large acquaintance of idealist and vocal people, representative of the spirit of the fin-de-siècle, modifies the perception of his personality as well as the study of his architecture. Linked to important but now forgotten personalities of bohemian Montmartre (Bans, Straus, Alcanter de Brahm) and to their modest but ambitious publication, La Critique, the young architect was supported and encouraged in his aesthetic search for a renewal – Renaissance – of the French arts. Beyond the extension of our biographical knowledge, the connection suggests new fields of research with the focus on the influence of occultist theories and science-fiction novels in the elaboration of the “Guimard style”, a unique expression in the history of art of the application of the energy of vegetation to architecture and the decorative arts.