This collection of essays deals with the attitude of Christians of the first and second centuries C.E. toward both (Jewish) unbelievers and semi-believers, fellow-Christians who are, in their opinion, people who do not adhere to a pure faith in Jesus Christ. It focuses on two New Testament writings (the Gospel of John and the Letter of Jude) and on the second century work The Testaments of the Twelve Patriarchs. It explains the texts in their historical and cultural environment, and serves to clarify the writers’ negative feelings about paganism, Judaism, and Christian heresies. The analyses here produce a number of new and surprising results, and will appeal to New Testament scholars and students, clergymen, and all those interested in the beginnings of Christianity and in the relationship between orthodox Christians, on the one hand, and Jews, non-Jews, and non-orthodox fellow-Christians, on the other.