Arithmancy

"If being good at Divination means I have to pretend to see death omens in a lump of tea leaves, I'm not sure I'll be studying it much longer! That lesson was absolute rubbish compared with my Arithmancy class!"

— Hermione Granger's opinion of Arithmancy

Arithmancy was a magical discipline that studied the magical properties of numbers, including predicting the future with numbers and numerology. Those who studied and practised Arithmancy were called Arithmancers.

Description

While the class offered as an elective to Hogwarts students from their third year and up primarily focused on predicting the future using numbers, the field also served the wizarding community more broadly as the wizarding equivalent to mathematics does in the Muggle world: the famous thirteenth-century Arithmancer Bridget Wenlock, for example, would write her calculations, including the one that established the magical properties of the number seven, in the form of theorems (a proposition or statement that is demonstrated in geometry, showing that mathematics plays at least a part in arithmetical work).

Curse-Breakers was also known to be required a passing grade on their O.W.L. exam in the subject, with the reason cited being that banking and transactions were part of their job, and when Cerberus Langarm confiscated the accounts ledger from Slug & Jiggers Apothecary in Diagon Alley, a "really, really long book of boring financial figures", as evidence in an ongoing investigation, and delegated the task of going through it to Mathilda Grimblehawk and her partner, who in turn passed it along to Sage Bragnam, as he had studied arithmancy.

History

Arithmancy was an elective subject offered from the third year on at Hogwarts School of Witchcraft and Wizardry, the homework assignments of which included writing essays that required the consultation and/or composition of complex numerical charts. Numerology and Grammatica was a textbook for this subject at Hogwarts that was used in the third year.

On 25 December 1995, Harry Potter gave his best friend Hermione Granger a copy of New Theory of Numerology as a Christmas present, whilst they were visiting St Mungo's Hospital for Magical Maladies and Injuries.

Notable Arithmancers

Wizard(s)	Notes
Bridget Wenlock	The archetypal example; she was a celebrated witch who first discovered the magical properties of the number seven in the 13th century.
Lucien Marque	Wrote the Compendium de Numérologie et d'Arithmancie.
Septima Vector	Taught Arithmancy and also likely Advanced Arithmancy Studies at Hogwarts School of Witchcraft and Wizardry for at least six years (possibly more).

Arithmancy texts

New Theory of Numerology, by Lukas Karuzos

Numerology and Grammatica

• Compendium de Numérologie et d'Arithmancie

Etymology

Arithmancer and Arithmancy come from the Greek αριθμός (arithmos), meaning "number", and μαντεία (manteia), meaning "divination". Hence "Arithmancy" literally means "number divination", which is fitting.

Behind the scenes

• In the real world, the term "Arithmancy" refers to a supposed form of divination based on assigning numerical values to words or phrases; the term "Numerology", referred to in canon as a branch of Arithmancy, refers to any of a number of different beliefs in a divine or mystical relationship between a number and coinciding events. It is unknown how similar Arithmancy is to basic Muggle mathematics.
• In the film adaptation of Harry Potter and the Prisoner of Azkaban, Hermione seems to choose Ancient Runes, not Arithmancy, as her favourite subject, comparing its superiority over Divination.
• In Harry Potter and the Prisoner of Azkaban, Hermione expressed open contempt for the subject of Divination, which she detested because it seemed to be "a lot of guesswork". On the other hand, she also also proclaimed that Arithmancy (in which numerology, a term that in reality refers to any belief in the divine or mystical relationship between a number and one or more coinciding events, is prominent) is her favourite subject. While this may seem contradictory at first, a likely explanation is that Arithmancy applies a more rigorous and mathematical approach to predicting the future, which the scientifically-inclined Hermione would respond well to.
• In Harry Potter: Hogwarts Mystery, Murphy McNully was known to accurately predict the outcome of certain events by calculating the probability of them taking place, be it the estimated chance of success of an attempted Quidditch strategy, or the behaviour of his fellow students. As the wizarding equivalent to mathematics, and given its predictive capabilities, Murphy possibly used Arithmancy in order to calculate probabilities.
• Tom Riddle may have chosen Arithmancy as an elective in his third year at Hogwarts, since later he would be aware of seven as the most powerful magical number.

Appearances

• Harry Potter and the Philosopher's Stone (video game) (First appearance) (GBC version only)
• Harry Potter and the Chamber of Secrets (First mentioned)
• Harry Potter and the Chamber of Secrets (video game) (Mentioned only)
• Harry Potter and the Prisoner of Azkaban (Mentioned only)
• Harry Potter and the Goblet of Fire (Mentioned only)
• Harry Potter and the Order of the Phoenix (Mentioned only)
• Harry Potter and the Order of the Phoenix (video game) (Mentioned only)
• Harry Potter and the Half-Blood Prince (Mentioned only)
• Harry Potter and the Half-Blood Prince (film) (Mentioned only) (Seen on book cover)
• J. K. Rowling's official site (Mentioned only)
• Pottermore (Mentioned only)
• HarryPotter.com (Mentioned only)
• Harry Potter Limited Edition (Mentioned only) (Seen on book cover)
• The Art of Harry Potter: Mini Book of Graphic Design (Mentioned only) (Seen on book cover)
• Wonderbook: Book of Spells (Mentioned only)
• Fantastic Beasts: Cases from the Wizarding World (Mentioned only)
• Harry Potter: Hogwarts Mystery (Mentioned only)
• Harry Potter: Wizards Unite (Mentioned only)
• Harry Potter: Magic Awakened (Mentioned in History of Magic classes)
• Hogwarts Legacy (Mentioned only)

External links

• Arithmancy on Wikipedia
• Arithmancy calculator