The research I conducted in an effort to familiarize myself with the institutions of the barbaric period as well as the free cities of the Middle Ages led me to further interesting research on the role played by the state during these three centuries, from the time of its last establishment in Europe. Additionally, the study of mutual aid institutions in various periods of civilization prompted me to investigate the way in which the development of ideas and ethics emerged in human society. Pyotr Alexeyevich Kropotkin, "Memoirs"