St. Gregory of Nyssa ca. 335-395
If one takes upon himself the name of Christ but does not practice the way of life associated with it, he falsely bears this name. Such a person is like a soulless mask with human features superimposed on a monkey. For just as Christ cannot be if He is not justice, purity, the Truth, and the estrangement from all evil, so cannot he who does not demonstrate the characterisitics associated with this name be a Christian. Thus, if it were necessary for someone to express the meaning of the word “Christianity” in a definition, we would say that it is the imitation of the Divine Nature. (To Harmonius)