Muggles' Guide to Harry Potter/Magic/Transfiguration

Overview
Transfiguration is the family of magical spells that are used for changing objects from one type of thing into another. At Hogwarts, Transfiguration is taught by Professor Minerva McGonagall.

Extended Description
Transfiguration covers a wide range of spells. At the low end of the scale, the first Transfiguration charm learned by Harry's class is changing a match into a needle; the more complex spells include changing creatures from one species to another. It also includes discussions of Animagi, though we don't see how to become one.

Apparently Transfiguration is a core course for all schools, not just Hogwarts, as we hear Professor McGonagall telling Neville, in Harry Potter and the Goblet of Fire, not to reveal that he has not yet mastered a simple Switching Spell. We note that this is the only mention of this spell, so we have no indication of how long Neville has been trying to learn it; from McGonagall's tone of exasperation, however, we believe it to be something assigned in an earlier year that Neville was still not able to perform to an acceptable level. McGonagall's concern about this perceived failure of teaching on her part would suggest strongly that Transfiguration, including Switching Spells, is taught at Beauxbatons and Durmstrang.

It is mentioned in The Tales of Beedle the Bard that Professor McGonagall had learned and carried out the Animagus transform as part of her research on Transfiguration. We also learn there that the Animagus transform allows the caster to retain human intelligence. While it is possible, theoretically, to Transfigure yourself into an animal, you would also end up with the animal's intelligence, and would be trapped in the form of that animal until some other wizard returned you to your human shape.

In Harry Potter and the Goblet of Fire, Viktor Krum uses partial transfiguration to give himself a shark's head so that he can breathe underwater. Clearly this is an exception to the rule above that prevents Transfiguring oneself into an animal. We assume that this is very advanced magic, as it would be necessary to give yourself the shark's face and gills, while keeping your brain human so that you can undo the spell afterwards.

Analysis
Transfiguration is largely a practical class, and as such is relatively noisy with students casting spells, and, at times, sounds from the animals used as subjects. As such, it is one of the places where the Trio feel able to discuss events. With the potential for spells to go wrong, it is also a place where there is a certain amount of slapstick humour. The possibilities of both conferences and humour, however, are more than slightly decreased by Professor McGonagall, a stern teacher who keeps a relatively tight control on her classroom.

As mentioned in the article on Charms, the distinction between Charms (which change what a thing does without changing its essential nature) and Transfiguration (which changes its essential nature) is somewhat loose. In Transfiguration class, we note Ron having trouble with a Silencing charm, and there is later mention of a Vanishing charm, where it is mentioned that it is more difficult to Vanish live animals than inanimate objects. Whether Silenced or Vanished, however, the object remains intrinsically the same, a silenced bullfrog is still a bullfrog, while a vanished rat, if it can be unvanished, does not lose its essential rat nature.

In the earliest Transfiguration classes, Professor McGonagall changes her desk into a pig and back again, and we later see lessons where the students are asked to Transfigure teapots into tortoises. This does raise an awkward question: does this form of magic allow the wizard to create life? This question is never addressed in the books.

We will assume that it is a literary device only that has most transfigurations being done between things with the same first letter. We have already mentioned teapots and tortoises, and beetles and buttons; a mistake in the Transfiguration OWL exams saw one student mistakenly creating a flock of flamingos rather than a ferret. We will note, however, that in the real world, our belief in magic was based on the doctrine of signatures, that held that, as all things were created by God, a similarity of appearance implied a relationship in effect. While there is much less belief in magic in the current day, the doctrine of signatures still underlies what belief there is. So deliberate use of similarity in name does tend to enhance the apparent authenticity of magic in the series.

Questions

 * 1) If transfiguration is just a spell (one spell or another), why was it so hard to master?
 * 2) What other limitations are there on transformation, other than how difficult it is?