The book by Doctor of Philosophy V.N. Demin (1942-2006) is dedicated to the outstanding thinker Lev Nikolaevich Gumilyov (1912-1992) - the son of the Silver Age poets - Nikolai Gumilyov and Anna Akhmatova. Having gone through many years of prisons and camps, non-recognition and obstruction, he became one of the most authoritative historians and philosophers of our time, who determined the development of science in the 21st century. The author of the book reveals the ideological roots and various aspects of L.N. Gumilev’s cosmist views, based on the doctrine of the biosphere and noosphere, Eurasian theory and the concept of passionarity. Based on the fundamental works of the scientist, he analyzes his research and original conclusions in the field of world and Russian history, showing the enduring significance of his ideological heritage for modernity and the science of tomorrow.