The Roman Emperor Flavius Valerius Constantine I is one of those few personalities in the history of mankind about whom it can be directly said that they turned the course of world history, and their works influenced the whole world and all times. Of course, before him, there were rulers in the Roman Empire who had no less political power. But they did not have a universal idea that gave their power a world-historical meaning. After Constantine, there were rulers who offered the world various fateful ideas. But they did not have the power that only the emperor of the Roman Empire could have. The unique combination of a great idea and great power allowed Constantine to do something more than just state reform: to found a new civilization - the Christian European civilization, which today includes countries in the colossal space from Russia to America.