The book offered to readers, written by the outstanding Russian philosopher and public figure, anarchist theorist P. A. Kropotkin, is one of his most famous works, along with such books as “Speeches of a Rebel” and “Bread and Freedom.” This book was (and still is) one of the most important works, from a scientific point of view proving the consistency of the program of socio-economic transformations proposed by the anarcho-communists. P. A. Kropotkin drew his ideas both from biology (the life of the animal world) and from his historical research, as well as contemporary social life. At the same time, he wrote about mutual assistance as a phenomenon that does not at all deny competitive relations. Nowadays, one can often hear the conclusions of scientists that are close to the theories of P. A. Kropotkin, which emphasizes the relevance of this work now, at the beginning of the 21st century. This publication is based on the most complete version of the work, including appendices and prefaces by the author; this was the last edition that P. A. Kropotkin prepared for publication with all the necessary corrections. The book is addressed to philosophers, historians, social scientists, as well as all readers interested in the heritage of Russian and world socialist thought.