The articles analyzes the original concept of immortality, presented by F.M. Dostoevsky in a handwritten sketch written on April 16, 1864, the day after the death of the writer’s first wife. The authors argue that this concept was created under the influence of the ideas of German romantic natural philosophy, in particular G.T. Fechner’s work of The Book of Life After Death (1836). According to the pantheistic ideas of Dostoevsky and Fechner, every person after death continues to exist in the (...) earthly world. Having lost a limited biological body in death, a person can get a more extensive “cosmic” body, covering significant areas of the material universe. His personal spirit continues to exist in mankind, and the degree of his influence depends on what kind of spiritual success he achieved during his lifetime. In the concept of Fechner and Dostoevsky, posthumous life can be very different: great personalities (Goethe, Shakespeare, Napoleon, etc.) acquire an even more significant being than during life, and they continue to influence humankind, which, developing in history, strives for an absolute “synthesis” -the merger of all people into an organic whole and at the same time the merger with the universe. Individuals who, during their lifetime, confined themselves to their selfish interests can even disappear. In this concept, God is defined as “universal Synthesis,” i.e., the goal of the world process and the final merging of everything with everything. Jesus Christ is understood as an absolute, perfect man who, after death, does not resurrect in his previous bodily form, but completely dissolves in humankind and acts as a force guiding it toward unity and synthesis with the material world. (shrink)