Why didn't Dumbledore use a portrait or a ghost as DADA teacher?

Question

The practical part of the lesson might be a bit challenging, but not impossible, and it definitely can be an improvement considering Umbridge's or Lockhart's lessons.

There are many advantages to be had: a very talented wizard can be selected who in the past proved himself in fighting dark wizards / creatures.

In fact, such a teacher doesn't need regular payment, so there can be more than one DADA teacher: for each subject the specialist can be selected. For example if there was a wizard who was famous for defeating banshee or vampires, then he can teach the relevant part in the course.

The teacher is already dead so a life won't be endangered every year by the course Voldemort placed on the position - it might even confuse the curse if there are dozens of DADA teachers present - after all, when Snape substituted for Lupin, nothing happened to him.

Let's take Harry as an example: He was the actual DADA teacher in his fifth year - he gave instructions to the group called DA about defense spells. A ghost and a couple of portraits could also do that and probably without getting the DADA curse.

So shouldn't Dumbledore whistle past the limitations of the portraits/ghosts and dig up a Merlin-calibre wizard to avoid hiring Fudge's puppet?

Answer 1

The answer to this question is your first sentence.

The practical part of the lesson might be a bit challenging,

DADA is one of the fields of magic that most frequently requires wand use. Charms is another field with heavy wand use, and it is being taught by an alive and powerful wizard Filius Flitwick.

So a ghost or a portrait cannot show the required wand movement to make a spell and they can't even show the effects of the spell. Yes, it would be better than Umbridge, but we know that Harry was opposed to learn only from books when Umbridge suggested it in DADA class. Now you are proposing the same thing.

Also the lessons of Lupin and Moody were very exciting for the students because both of the teachers actively used their wands. Your portrait or ghost teacher can not demonstrate a fight with a boggart as they can not make a spell. They also can't teach Harry or someone else to make the Patronus charm.

The only lesson in Hogwarts that is taught by a ghost is History of Magic (a field with virtually no wand use), but we know that Harry always falls asleep in this course. It is not a good experience for a student also not appealing to participate.

Finally, a dead person, ghost or a portrait, may not have the same concern about defending itself against Dark Arts or killing curses with the student who is currently alive. Because,

what is dead may never die.

So they won't be in Constant Vigilance! Alastor Moody

Answer 2

In Tales of Beedle the Bard, J.K. Rowling says:

Wizarding photographs and portraits move and (in the case of the latter) talk just like their subjects. Other rare objects, such as the Mirror of Erised, may also reveal more than a static image of a lost loved one. Ghosts are transparent, moving, talking and thinking versions of wizards and witches who wished, for whatever reason, to remain on earth. JKR

_{Tales of Beedle the Bard - Babbity Rabbity and the Cackling Stump - Page 79 - Bloomsbury}

I think it's important to distinguish between ghosts and portraits (and photographs).

Ghosts retain sentience; they would be capable of teaching a class, in that they could verbally interact in real time with the students. However, they would not be able to produce magic or, say, reliably wield a wand. A wand is essential for Defence Against the Dark Arts. Being able to cast magic is essential as well.

A portrait is not fully sentient (Phineas Nigellus seems to be an exception to the rules of portraiture, as he interacts with other characters in real time, and is able to roam from one frame to another, depending.). Portraits retain an essence of the person they represent -- enough to lead some to believe they are fully sentient when in fact they are not. For lack of a better term, portraits are able to deliver platitudes that are reminiscent of their subject. But they are limited in how deeply they can communicate, which is to say they don't interact deeply at all. Full sentience would be essential for teaching, especially in a class like Defence Against the Dark Arts. Yes, they are more than a static image, but they are not operating with a full repetoire of thought and knowledge.

Dumbledore likely didn't hire a ghost or portrait to teach DADA because a ghost cannot produce or demonstrate magic, and a portrait is not sentient enough to effectively interact with students in a teaching situation. To hire a ghost or portrait for DADA would be cheating the students in a way, because they would not receive the best DADA instruction available.

One might argue that Dumbledore certainly wasn't providing the students with the best DADA instruction when he hired Gilderoy Lockhart, but remember Gilderoy was the only applicant for the DADA position that year!

Answer 3

Overall, Portraits and/or Ghosts would make for lousy professors. As seen below, their limited interaction with the living world would a severe hindrance in the teaching of any practical magic.

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Portraits

JKR on Portraits, emphasis mine;

Hogwarts portraits are able to talk and move around from picture to picture. They behave like their subjects. However, the degree to which they can interact with the people looking at them depends not on the skill of the painter, but on the power of the witch or wizard painted.

When a magical portrait is taken, the witch or wizard artist will naturally use enchantments to ensure that the painting will be able to move in the usual way. The portrait will be able to use some of the subject’s favourite phrases and imitate their general demeanour. Thus, Sir Cadogan’s portrait is forever challenging people to a fight, falling off its horse and behaving in a fairly unbalanced way, which is how the subject appeared to the poor wizard who had to paint him, while the portrait of the Fat Lady continues to indulge her love of good food, drink and tip-top security long after her living model passed away.

However, neither of these portraits would be capable of having a particularly in-depth discussion about more complex aspects of their lives: they are literally and metaphorically two-dimensional. They are only representations of the living subjects as seen by the artist.

Some magical portraits are capable of considerably more interaction with the living world. Traditionally, a headmaster or headmistress is painted before their death. Once the portrait is completed, the headmaster or headmistress in question keeps it under lock and key, regularly visiting it in its cupboard (if so desired) to teach it to act and behave exactly like themselves, and imparting all kinds of useful memories and pieces of knowledge that may then be shared through the centuries with their successors in office.

The depth of knowledge and insight contained in some of the headmasters’ and headmistresses’ portraits is unknown to any but the incumbents of the office and the few students who have realised, over the centuries, that the portraits’ apparent sleepiness when visitors arrive in the office is not necessarily genuine.

So we can see that a portrait can only have limited interaction with the outside world unless a couple criteria are met 1) the wizard is very powerful, and 2) the portrait has been taught all the information from the subject of said portrait. So, to have a portrait that can teach classes, it must have been designed to do so from the start. You could not just take a portrait of a wizard who did well in a subject and have it teach.

Also from a practical aspect, a portrait will not be able to cast spells in the real world, making it difficult to demonstrate them and their effects. Classes like Charms, Transfiguration, and DADA are all heavy on spell casting and would need the nuance of live interaction.

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Ghosts

JKR on Ghosts, emphasis mine;

In the world of Harry Potter, a ghost is the transparent, three-dimensional imprint of a deceased witch or wizard, which continues to exist in the mortal world. Muggles cannot come back as ghosts, and the wisest witches and wizards choose not to. It is those with 'unfinished business', whether in the form of fear, guilt, regrets or overt attachment to the material world who refuse to move on to the next dimension.

Having chosen a feeble simulacrum of mortal life, ghosts are limited in what they can experience. No physical pleasure remains to them, and their knowledge and outlook remains at the level it had attained during life, so that old resentments (for instance, at having an incompletely severed neck) continue to rankle after several centuries. For this reason, ghosts tend to be poor company, on the whole. They are especially disappointing on the one subject that fascinates most people: ghosts cannot return a very sensible answer on what it is like to die, because they have chosen an impoverished version of life instead.

The most productive ghost at Hogwarts is, of course, Professor Binns, the old History of Magic teacher who fell asleep in front of the staff-room fire one day and simply got up to give his next class, leaving his body behind. There is some debate as to whether or not Professor Binns realises he is dead. While his entrance to lessons through the blackboard is vaguely amusing the first time students see it, he is not the most stimulating teacher.

So again, there limitation placed on how a ghost can interact with the living. With there needing to be a reason for a ghost to stay behind, I doubt many would have "guilt, fear, or an overt attachment" to teaching. Professor Binns seems to be the exception to this, and it is sometimes question whether or not he knows he is dead...