The currently widespread appeal to the faith of the fathers - Orthodoxy - is not always, unfortunately, crowned with a correct understanding of it. Fulfillment of all church institutions without understanding the essence of Orthodoxy can easily lead a believer to acquire not God-like properties of humility and love, but directly ungodly ones: conceit, pride, pharisaism. How to reach the saving haven and enter the Kingdom of God is, as the fathers put it, the science of sciences and the art of art. That is why the peculiarity of Orthodoxy is so important that it, unlike all other areas of modern Christianity that explore this science according to their own understanding, is completely based on patristic teaching and experience. The answer to the question, what is Orthodoxy and how to live in accordance with Orthodox teaching , and this book of letters is dedicated to one of the remarkable ascetics of our Church of the 20th century, Abbot Nikon (Vorobyov).