Diadochus, bishop of Photike in Epirus (ca. 400-ca. 487), is among the earliest witnesses to the Jesus Prayer. In his theology he puts much stress on man’s experience of God – how his presence and love are felt in the “sense of the heart”. In my paper I will especially study what is meant by “experience” (peira) – how it is described and how it relates to prayer, contemplation and knowledge.