Summary
Summary of On Demoniality: On Incubi, Succubi & the Nature of Demons
On Demoniality: On Incubi, Succubi & the Nature of Demons at a glance
Summary: 8 min to read
- Reading time
- About 1 h 45 min1 h 25 min fast, 2 h 5 min slow
- Length
- 25,300 words
- Library level
- Challenging long sentences, a rich vocabulary
- First published
- 1875by Ludovico Maria Sinistrari
Reading time at 238 words a minute (fast 300, slow 200). How long the classics take to read · Updated
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Key ideas
Key idea 1
Judgment begins with the demon's nature
A married woman in Pavia receives a cake she never baked. That night, a thin, hissing voice asks whether she enjoyed it. This strange visit opens a question that matters to Sinistrari as a friar and theologian: what kind of being is approaching her?
He writes for judges, confessors and inquisitors who must weigh intercourse with demons. Before they can judge its gravity, he argues, they must understand the creature involved. His bold proposal is that incubi are rational, mortal beings with fine bodies of their own.
Key idea 2
A separate act needs a separate name
Sinistrari begins by resisting an inherited label.
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Key idea 3
The witch's pact comes before intercourse
When Sinistrari turns to witches, he places the pact at the center of the case.
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Key idea 4
Some visitors seek affection without worship
Another kind of visitor does not ask for sacrifice, homage or rejection of faith.
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Key idea 5
Borrowed seed leaves fatherhood unexplained
The common explanation says that a succubus steals human seed and an incubus uses it to produce a child.
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Key idea 6
Silence does not rule out subtle bodies
Before arguing that such creatures exist, Sinistrari asks whether they are possible.
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Key idea 7
Bodily responses suggest a natural creature
Sinistrari moves from possibility to evidence.
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Key idea 8
Older accounts support creatures between kinds
Sinistrari turns to religious accounts for support.
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Key idea 9
The creature's nature guides the judgment
The argument brings Sinistrari back to the practical work of judging conduct.
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Go deeper: the whole of On Demoniality: On Incubi, Succubi & the Nature of Demons
About 1 h 50 min to read.Start freeWho it’s for
Readers who love the odd corners of religious history, the logic of baroque scholars, and the folklore of spirits and witches will find a rich study of how learned men reasoned about the unseen.
What this book is
Picture a married woman in the Italian city of Pavia. A cake she never baked arrives with her loaves from the oven. That night a thin, hissing voice whispers in her ear and asks whether she enjoyed it.
On Demoniality is a treatise by Ludovico Maria Sinistrari, an Italian friar and theologian who died in 1701. He wrote it as a working guide for judges, confessors and inquisitors. To weigh the gravity of intercourse with a demon, he says, one must first know what a demon is. You get his bold opinion that incubi are rational, mortal creatures with fine bodies of their own.
In this summary
- 1Judgment begins with the demon's natureFree
- 2A separate act needs a separate name
- 3The witch's pact comes before intercourse
- 4Some visitors seek affection without worship
- 5Borrowed seed leaves fatherhood unexplained
- 6Silence does not rule out subtle bodies
- 7Bodily responses suggest a natural creature
- 8Older accounts support creatures between kinds
- 9The creature's nature guides the judgment
Demoniality is a sin of its own kind
Sinistrari opens with a question of naming. The word Demoniality was coined by John Caramuel. Before that, the schools filed intercourse with a demon under bestiality. Saint Thomas Aquinas defined bestiality as intercourse with something of a different species, and other moralists read that as covering demons too.
Sinistrari disagrees. In his view Aquinas meant a living animal. A human corpse is also a thing of another species, yet nobody calls intercourse with a corpse bestiality. It is called pollution. So the phrase cannot stretch to cover anything at all.
He offers more proofs. A demon differs from a beast by genus, since one has a body and the other, in common teaching, has none. Moralists call intercourse with a demon more grievous than intercourse with an animal, yet within one species every act weighs the same. Nor can the extra weight come only from worship, since some incubi ask for no homage at all.
Before you judge an act, be exact about what kind of act it is.
That’s 1 of 9 key points.
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Check yourself
Why does Sinistrari first ask what kind of being a demon is?
Right. “To weigh the gravity of intercourse with a demon, he says, one must first know what a demon is.”Not quite. “To weigh the gravity of intercourse with a demon, he says, one must first know what a demon is.”
What distinguishes the second kind of visitor from the demons involved in witches' pacts?
Right. “These demons demand no homage, no sacrifice and no renunciation of faith.”Not quite. “These demons demand no homage, no sacrifice and no renunciation of faith.”
What does Sinistrari propose instead of the stolen human seed theory?
Right. “That leads him to his bold thesis, offered under the correction of the Church: the incubus begets the child from his own seed.”Not quite. “That leads him to his bold thesis, offered under the correction of the Church: the incubus begets the child from his own seed.”
Go deeper: the whole of On Demoniality: On Incubi, Succubi & the Nature of Demons
About 1 h 50 min to read.Start freePaperback, hardcover and large print, printed for you at cost, are on their way.Email me when it is printed
About this edition
Every format is free to start, and print and large print are at cost.
- LengthAbout 25,300 words
- Reading timeAbout 1 h 45 min
Questions about On Demoniality: On Incubi, Succubi & the Nature of Demons
What is On Demoniality about?
It is a scholastic treatise on sexual intercourse between humans and demons. Sinistrari defines the sin, describes witches' pacts, argues that incubi are rational creatures with subtle bodies, and then sets out how courts should weigh, prove and punish the crime.
What is the difference between demoniality and bestiality?
Sinistrari says bestiality is intercourse with a living beast, while demoniality involves a demon who, on the common teaching, uses a lifeless body moved from outside. He argues they differ in kind, in confession and in gravity.
What are incubi and succubi in this book?
An incubus is a male demon who seeks intercourse with women, and a succubus a female one who seeks men. Sinistrari reasons that some are not fallen spirits but mortal rational beings with fine bodies of air, water or fire.
Who was Ludovico Maria Sinistrari and when did he write?
He was an Italian Franciscan theologian who died in 1701, and the book belongs to the late seventeenth century. He writes as a professor and adviser, drawing on Aquinas, Augustine, Scripture and his own cases from Pavia.
Is On Demoniality easy to follow?
Its numbered paragraphs move step by step, and it is full of stories such as the cake, the vanishing dinner table and the herb remedies. Each argument is stated, tested against objections and then summed up.
Cite this edition
Sinistrari, Ludovico Maria. On Demoniality: On Incubi, Succubi & the Nature of Demons. Library of Alexandria, 2026, libraryofalexandria.com/products/on-demoniality-on-incubi-succubi-the-nature-of-demons.
Sinistrari, L. M. (2026). On demoniality: On incubi, succubi & the nature of demons. Library of Alexandria. https://libraryofalexandria.com/products/on-demoniality-on-incubi-succubi-the-nature-of-demons (Original work published 1875)
Sinistrari, Ludovico Maria. On Demoniality: On Incubi, Succubi & the Nature of Demons. Library of Alexandria, 2026. https://libraryofalexandria.com/products/on-demoniality-on-incubi-succubi-the-nature-of-demons.
@book{sinistrari2026demoniality,
author = {Sinistrari, Ludovico Maria},
title = {On Demoniality: On Incubi, Succubi \& the Nature of Demons},
publisher = {Library of Alexandria},
year = {2026},
url = {https://libraryofalexandria.com/products/on-demoniality-on-incubi-succubi-the-nature-of-demons},
note = {First published 1875}
}
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