sentences:  He also edited the most important cultural history review of the day, "Freie Bühne“ (Free Stage) and popularized his free-thinking monism knowledge - especially the innovating school of Charles Darwin and Ernst Haeckel in dozens of self-edited books and series released by Kosmos-Verlag in Stuttgart collaborating with the Berlin artist Heinrich Harder.His friendship with the Hauptmann brothers, Gerhart Hauptmann and Carl, brought Bölsche to Schreiberhau in the Riesengebirge mountains, where he would spend the summer regularly, starting in 1901, making his permanent residence there in 1918.He continued to devote himself to his literary work and his extensive correspondence until old age.