This book presents one of the answers to the question: `What is Orthodoxy?`. The texts included in the book belong to both secular and ecclesiastical thinkers; some of them, published abroad 70-80 years ago, appear in Russia for the first time. The authors of the articles talk about Orthodoxy in general and about Orthodoxy in Russia. The book is of interest not only for religious scholars and theologians, not only for Orthodox believers, but for everyone who cares about the history and culture of Russia. It can serve as a textbook in a number of academic disciplines, or it can simply be a fascinating and educational read.