Defensive Magical Theory

Defensive Magical Theory is a Hogwarts School of Witchcraft and Wizardry textbook written by Wilbert Slinkhard. Released in, or prior to 1995, it was used by Dolores Umbridge in Defence Against the Dark Arts classes to ensure the students were taught defensive magic in a "secure, risk-free way."

Known Contents
In Chapter 15, the author expresses his opinion that counter-jinxes are not named properly, because he believes that "counter-jinx" is a term simply used to make jinxes seem more acceptable. Apparently, Slinkhard disapproves of the use of jinxes. From this opinion, as well as from the chapter titles and the fact that Dolores Umbridge approves of the book, it can be assumed that Defensive Magical Theory discourages the use of any defensive magic that could be used aggressively. Hermione Granger strongly disagreed and expressed her opinion in one of Professor Umbridge's Defence Against the Dark Arts classes. Although Umbridge was initially impressed that Hermione had read the entire book and was able to quote it, she was quickly irritated when Hermione critiqued the text, and coldly deducted points from Gryffindor for "disrupting [her] class with pointless interruptions".

The contents of this book are extremely boring, as Harry Potter compared reading it to listening to the teacher of History of Magic, Professor Cuthbert Binns, whose droning is enough to put most students to sleep. Harry found himself re-reading the first line half a dozen times, while Ron Weasley was staring at the same spot for a long time.

In 1997, Hermione considered this book as she was sorting supplies for their mission to find Voldemort's Horcruxes. She tossed it into the trash without a second glance.

Known Chapters

 * Chapter One: "Basics for Beginners"
 * Chapter Two: "Common Defensive Theories and their Derivation" (page 19)
 * Chapter Three: "The Case for Non-Offensive Responses to Magical Attack" (page 34)
 * Chapter Fifteen: (unnamed) chapter concerning counter-jinxes
 * Chapter Thirty-four: "Non-Retaliation and Negotiation"

Behind the scenes

 * In the film version of Harry Potter and the Order of the Phoenix, the Dark Arts Defence: Basics for Beginners book is used for Umbridge's classes, rather than this book. It has the same level of contents of theories on Defence, rather than practical information on countering the Dark Arts.

Appearances

 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Deathly Hallows

Notes and references
Théorie des stratégies de défense magique Теория защитной магии