John Henry Blunt - Dictionary of Sects, Heresies, Ecclesiastical Parties, and Schools of Religious Thought (1874)
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This is one of those books that invites long browsing, at least for certain types of readers. From a historical point of view it's extensive, almost obsessive, documentation that Christianity has always been a contentious mix of varying viewpoints. If like me you're not quite so interested in the theology it's the constant parade of oddities and peculiar beliefs that make it worthwhile. The effect at times is almost Borgesian with the references and wayward information and almost off-hand tone to the strangest statements (and don't forget that "Tlon, Uqbar, Orbis Tertius" opens with discussion of a heresiarch and an encyclopedia).
Let's flip through just "A". Even right at the start we encounter "Abelonites" from 4th or 5th century who "adopted the eccentric practice of marrying wives without procreating children, in supposed imitation of Abel, who was stated to have had a wife, but not to have known her; and in lieu of the consummation of marriage, and at the same time to enable them to perpetuate their sect, the husband and wife adopted two children of different sexes, who in their turn were to abstain from all intercourse, and on the death of their foster-parents to resort to the same plan of adoption." No wonder the Abelonites died out. (And seriously was the general level of writing ability just that much better in the late 19th century? Or do I just have a weakness for long sentences?)
"Agoniclites" were a "fanatical sect of the seventh and eight centuries, whose distinctive tenet was the condemnation of kneeling as the attitude of prayer. They are said also to have used dancing as a devotional custom."
And how many bookish people (or ones interested in the synoptic problem) would not read the long entry on "Alogi" who "denied St. John's doctrine concerning the Logos, and who consequently rejected St. John's writings."
"Artoryritae" "used cheese as well as bread in the celebration of the Holy Eucharist". The "Artemonites" had a confessor who recanted "on being warned of his error by a severe flagellation (attributed to angelic hands) during his sleep". The "Ascodrugitae" "danced around a richly-vested inflated wine-skin placed on an altar in their fanatical revels". The "Apoctactics" didn't just give up private property but "held that a renunciation of property is necessary to salvation". The "Abecedarians" "claimed to have direct inspiration from God, and maintained that this inspiration was obstructed by human learning. They carried this theory to such a length as to declare that it was desirable never even to learn ABC, since all human learning is founded on the alphabet".
Then there's "Angelici" mentioned by Epiphanius who knew nothing except the name. That didn't stop him from speculating about what they might have believed or Blunt from speculating further in some detail about whether they worshipped angels. Basically two writers centuries apart heard a name only and then invented further information though at least they were clear that's what they were doing.
Blunt was a professional chemist who gave that up to study then become a Church of England priest. He wrote an annotated Book of Common Prayer and several histories and commentaries. Perhaps because he was a practicing priest is why he seems to pay particular attention to heresies related to the sacraments in this book though overall he seems pretty even-handed even if very clear where he stands.