“Theoria” is from the Greek θεωρία, from which we get the English word “theory”. It can refer in general to the contemplation of the nature of things, but in Orthodox use it means “contemplating” or “beholding” in the fullest sense: the experience of true knowledge by love and union — a knowledge involving the whole person and not merely the mind. Theoria is the highest spiritual level of contemplative prayer in full communion with God.