The book briefly outlines the important teaching of the great holy father of the Orthodox Church, St. Gregory Palamas (1296-1359) on the difference between essence and energy in God. This teaching has been inherent in church theology since the earliest times and points to the ideal of Orthodox spirituality - salvation, deification and the vision of God, which is achievable for a person in part even while still on earth. In this edition, this teaching is placed in the broad context of the patristic teaching on the knowledge of God and its types - revelation and natural. At the same time, the author-compiler also touches upon the moral conditions of knowledge of God.