However, as is well known, along with the external enemies of Christianity—Jews and pagans—various internal enemies—false teachers and heretics—appeared as early as the Apostolic times. They considered themselves Christians and surreptitiously replaced the Truth of Christ with an heretical fallacy. St. Paul refers to these people as “having a form of godliness, but denying the power thereof” (II St. Timothy 3:5), and advises his disciple Timothy to turn away from such people. Likewise, St. John the Theologian writes: “They went out from us, but they did not really belong to us: for if they had belonged to us, they would no doubt have remained with us” (I St. John 2:19). He explicitly calls these people “antichrists” (2:18) and commands True Christians not to greet them or to receive them in their houses (II St. John 10-11).