A fan fiction of Harry Potter, by Eliezer Yudkowsky.
What if Aunt Petunia had married a scientist instead of Vernon Dursley?
Harry is an orphan raised by his aunt and her husband. He knows everything
about the scientific method, and has read loads of fantasy and sci-fi, and for
some reason he is also intellectually gifted. When the letter from Hogwarts
arrives, Harry accepts the fact that magic exists, that he is a wizard, and
that he will have the opportunity to study magic using the scientific method.
In Hogwarts, he is sorted in Ravenclaw, and so is Hermione Granger. Upon
meeting Draco Malfoy, he decides to introduce him to the methods of
rationality, in order to make him change his mind regarding the need for Blood
Purity, with proof that mixing with Muggles is not the reason why magic is
becoming weaker (rather, powerful spells are not transmitted to the next
generation). Harry also experiments on Magic with Hermione and discovers
that contrary to what he is being taught, Transfiguration is possible on parts
of objects, once the object is considered at the quantic level. Having a day
cycle of 26 hours, Harry is secretely given a Time Turner and the Invisibility
Cloak, which he immediately abuses to experiment on, and gets a reputation for
having greater powers than Dumbledore. Professor Quirrel decides that teaching
Defence against the Dark Arts requires more than the official curriculum, and
organizes his students in three armies, with, for the first-years, Draco,
Hermione and Harry as generals. The armies have regular battles, forcing the
students to learn about tactics, strategy, cunning, courage… all things that
Quirrel considers necessary for citizens to know, if they need to face
again a Dark Lord like Voldermort. Harry and Quirrel start an apprentice-master
relationship, Harry revealing that he has a secret inner dark side and a will
to take over the world in a benevolent fashion, to repair injustice and
prevent stupidity. During the lesson about defending oneself against Dementors,
Harry is unable to cast a Patronus and psychologically wounded when his wand
enters in contact with the Dementor. On a second attempt, Harry discovers that
a happy thought is not enough for a Patronus, but rather reasons that the
Dementors are holes in the fabric of reality leading to death; his hatred for
death and his will to one day find a way to immortality allows him to produce
a Patronus shaped as a Homo Sapiens and to destroy the Dementor by closing the
hole (what was thought to be impossible). Quirrel then asks Harry to go to
Azkaban and free Bellatrix Black, who has been imprisoned without trial and
was not responsible for her actions, being under the Imperio curse. Wanting to
repair the injustice, Harry agrees; Quirrel's plan gets wrong when Harry
prevents him from killing a guard and his magic interferes with his teachers',
rendering the latter unconscious. Harry manages to hide from the Dementors, to
make a hole into the metallic wall of the cell (by partially transfiguring a
large ring of metal into oil and just pushing the piece out) and escape with
Quirrell and Black, using a rocket-boosted broom to escape the anti-broom
charms on the prison. Harry wonders how Magical Britain can allow a place like
Azkaban to exist and decides that once he becomes master of the world, he
would destroy the prison. Later, a discussion with Dumbledore about heroes
(and the fact that Harry, like Dumbledore in his youth, is destined to be a
hero) triggers Hermione to want becoming a heroine; with a group of friends,
they fight bullying in the corridors of Hogwarts. This causes a large group of
bullies to trap the heroines, who are miraculously saved (by invisible Harry
and Quirrel). Hermione is then depressed that she is not able to be heroine. In
the final battle of the armies, Hermione wins against Harry and Draco; the
latter is angry and provokes her into a (secret and forbidden) duel. The next
morning, Draco in his hospital, and Hermione is accused of attempted murder,
even if the only reasonnable explanation is that both her and Malfoy are the
victims of a False Memory charm, probably caused by Voldemort. Hermione is
tried in front of the Wizengamot, where Lucius Malfoy wants revenge. Harry,
against Dumbledore's advice, uses a legal loophole and gets into debt with
Malfoy to buy Hermione's freedom, preventing her from being sent to Azkaban.
Soon after, Hermione is killed when a troll enters Hogwarts, and Harry becomes
very gloomy; Hermione's body is also stolen; there is not doubt anymore that
Voldemort has returned. Moreover, Quirrel is becoming more visibly sick and
reveals that he won't last long. On the day of the Quidditch championship,
Harry is baited into going back in time and caught by Voldermort. Together
they go through the various traps protecting the Mirror where the
Philosopher's Stone is hidden. Voldermort explains his motivation: the
Voldermort character was at first a prank, a way for Tom Riddle, posing as
David Monroe, to appear a hero after defeating a Dark Lord. He soon discovered
that it was much more entertaining to be evil, and when he got bored, he
decided to create an opponent worthy of himself by imprinting some of his
thought patterns into baby Harry's mind. Voldermort had also created
hundreds of horcruxes and lost them all over the world, one of them being even
the golden plaque onboard the Pioneer 10 space probe, becoming impossible to
kill. Voldemort also reveals that the Philosopher's Stone is a old magical
device that makes Transfiguration permanent, stolen from Baba Yaga by
Perenelle who then hid herself as Nicolas Flamel. Upon reaching the Mirror,
Voldemort obtains the Philosopher's Stone and traps Dumbledore, who had just
arrived, into the Mirror. Voldermort then takes Harry to a cemetary where,
after recreating his own body, he revives Hermione, as promised to Harry
(Harry had transfigured Hermione's body into a ring to keep it close) and even
gives her the regeneration power of a troll and the goodness and purity of a
unicorn. Harry is then surrounded by Death Eaters who just arrive, called by
their master. Voldermort makes Harry take an Unbreakable vow never to destroy
the World (which he suspects Harry would unwillingly do, according to
some prophecies). After that, he tells Harry he will kill him. While
psychologically torturing Harry to tell him things he the Dark Lord doesn't
know (and that would kill him, according to another prophecy), Harry finds a
way to escape by partially transfiguring the tip of his wand into a carbon
nanotube wrapped around the Death Eaters and Voldermort's wrists. By
tightening it, he kills the minions and renders Voldermort unconscious; he
then Transfigures him into another ring, fakes the scene so as not to appear
having been involved and leaves the place to tell McGonagall about the events.
Harry then receives imporant responsibilities in Magical Britain by
Dumbledore's will. He also puts into motion the creation of a hospital where
people (magical folks and Muggles alike) can be made immortal, and the
displacement of Azkaban's inmates to more human prisons. He also starts
talking Hermione into destroying the Dementors, letting her become a heroine.