Magic is a natural force that can be used to override the usual "laws of nature", but is still considerably scientific in how it operates. It is what all wizards and witches and in the Wizarding world use to do what they do. Most humans do not know that magic truly exists. There is a constant hiding from Muggles which must be done by wizards and witches.
- "Elf magic isn't like wizard's magic, is it?"
- —Ron Weasley[src]
In humans, the ability to perform magic or the lack of such ability is an inborn attribute. It is the norm in the children of magical couples and rare in those of Muggles. Exceptions do exist: those unable to do magic who are born to magical parents are known as Squibs, whereas a witch or wizard born to Muggle parents are known as Muggle-borns, or the pejorative "Mudbloods". The latter form are far more common than Squibs, but this may be a feature of the disparate sizes of the Muggle and wizarding populations.
Other magical creatures in the Wizarding world can also perform magic, such as house-elves and goblins. The house-elf Kreacher demonstrated the ability to disapparate from the kitchens of Hogwarts where humans cannot.
For a person's ability to perform magic to be useful, a good deal of training is required to acquire the correct discipline. When 'wild', typically with young and untrained children, it will still manifest itself subconsciously in moments of strong apprehension, fear or anger. A powerful or intelligent wizard or witch can direct this force in less random ways, eg. Tom Riddle, Lily Evans and possibly Ariana Dumbledore.
Almost all human magic is done with the use of a supporting tool or focus, typically a wand. One can do unfocused and uncontrolled magic without a wand. A few advanced wizards could perform directed magic without a wand.
A wizard or witch is only at their best when using their own wand. When using another's wand, one's spells are not as strong as they normally would be - due to the laws of Wandlore.
Regardless of how powerful a witch or wizard is, they are by no means without limits. For instance:
Rule of Conjuration: while it is possible to conjure things out of thin air, it is far more tricky to create something that fits an exact specification rather than a general one; moreover, any objects so conjured tend not to last.
Rule Against Resurrection: It is also impossible to resurrect the dead. Corpses can be transformed into obedient Inferi on a living wizard's command, though they are little more than zombies with no soul or will of their own. It is also possible via the rare Priori Incantatem effect to converse with ghost-like "shadows" of magically murdered people. The Resurrection Stone also allows one to talk to the dead, but those brought back by the Stone are not corporeal, nor do they wish to be disturbed from their peaceful rest.
Rule Against Immortality: Likewise, it is impossible to make oneself immortal unless one makes use of a mystical object of great power to sustain life (such as the Philosopher's Stone created by Nicolas Flamel or a Horcrux, the latter having been used by Lord Voldemort and Herpo the Foul). If one were to possess the three Deathly Hallows, it is fabled that they would possess the tools to become the "master of death". However, being a true "master of death" is to be willing to accept that death is inevitable.
The Five Exceptions
There are five exceptions to the defined laws of what elements one cannot transfigure by use of magic (Gamp's Law of Elemental Transfiguration). The five exceptions, are said to be: food, love, life, information and money.
Love Magic/Blood Magic
At least one known loop-hole exists to prevent the immediate murder of a wizard. A witch or wizard who willingly sacrifices themselves to protect another will give the one they protected a measure of immunity from their would-be-murderer. For example, Voldemort could not even bear to touch Harry Potter, as he was protected by his mother's sacrifice. Voldemort attempted to overcome this obstacle by using Harry's blood in his resurrection; however, since Lily's magical protection was in Harry's blood and his blood now flowed through Voldemort's new body, this actually meant that Harry could not be killed by Voldemort while Voldemort himself was still alive. When Voldemort attempted to kill him in May of 1998, Harry was, however, sent to a sort of limbo, where he was given the option of returning to the living world or moving on.
Magic and Emotions
A witch or wizard's emotional state can affect their inherent abilities.
- Nymphadora Tonks temporarily lost her power as a Metamorphmagus after suffering severe emotional turmoil when Remus Lupin would not return her affections. In effect, the form of her Patronus changed to reflect her love for him. In 1995, when Mad-Eye called her by her first name, her hair temporarily turned red.
- As related to Harry by Dumbledore, Merope Gaunt only demonstrated any magical ability when removed from her father's oppression, but then seemed to lose it again when her husband abandoned her.
- Ariana Dumbledore (Dumbledore's sister), was emotionally scarred at a young age, and thus her magic was volatile and uncontrolled.
- Harry Potter magically inflated his Aunt Marge, wandless and nonverbally, out of sheer anger when she disrespected his parents by calling his father a drunk.
- Ron Weasley caused it to snow above him with his wand when he felt guilt over Lavender Brown without using any worded spells.
Magic and Death
- Like love, death is studied in detail in a room (called the Death Chamber) of the Department of Mysteries containing an enigmatic veil (this suggests some sort of portal between the worlds of the dead and the living, but the exact significance of the veil is unclear). Anybody that falls or goes through the Veil dies, such as when Sirius Black was blasted through by his Death Eater cousin.
- Magical techniques have been used to prolong life. The Philosopher's Stone can be used to prepare a potion that postpones death indefinitely.
- Lord Voldemort has availed himself of other methods, being one of the few wizards ever to use Horcruxes in his long sought attempt to "conquer death", and is believed to be the only one to use multiple Horcruxes.
- Also, the drinking of Unicorn blood will keep a person alive even if death is imminent, but at the terrible price of being cursed forever.
- Being magical can contribute to one's longevity, as there are several characters in the series who are quite long-lived — Albus Dumbledore, Griselda Marchbanks, and Bathilda Bagshot, for example. This can mainly be attributed to the speed and effectiveness of magical healing, such as spells that can mend bones instantly, potions that can completely regrow them, further potions that can cure many sicknesses and ailments including the Common Cold, spells for instantaneous, scarless healing, and transportation to hospitals being a matter of a few seconds and a side-along apparator or a handful of Floo powder.
- It is revealed by Nearly Headless Nick that wizards have the option of becoming ghosts when they die. The alternative is "passing on". All Hogwarts headmasters appear in a portrait when they die, allowing consultation by future generations.
Magic and Love
Arguably the most powerful form of magic is also the most mysterious and elusive: love. Lord Voldemort, having never experienced love himself, underestimated its influence—to his detriment. It was through love that Lily Evans was able to save her son Harry from death by sacrificing her life so that he might live. Harry used very much the same mechanism to negate the power of Voldemort's spells against the students and teachers of Hogwarts. The exact nature of how "love-magic" works is unknown; it is studied in-depth at the Department of Mysteries where they have a giant cauldron of Amortentia.
The Wizarding World
The wizarding society exists as a shadow society to the Muggle world and works as hard as it can to keep its existence a secret, save for all but a few Muggles, such as those who are related to witches and wizards, or important Muggles such as the Prime Minister. To most magical people the Muggle world is unknown, and their attempts to disguise themselves as Muggles often have mostly humorous results. Muggle Studies at Hogwarts is considered a soft option. Most things of magical nature are hidden or otherwise obscured from Muggles; others (such as Dementors) simply cannot be seen by them, but Muggles do feel the effects of them. There is also an office in the Ministry of Magic, for the Misuse of Muggle Artifacts, that deals with people charming objects typically found in a Muggle society.
Different Types of Magic