You're having trouble with it because you're thinking solely in capabilities. Yes, it is possible for most wizards to be able to kill a dragon, if they want to and are skilled enough to cast the Killing Curse. However, the only people who are willing to do that are Dark Wizards because good people do not use the Killing Curse.

It's not a matter of whether or not you can kill the dragon, but a matter of whether you're willing to use dark magic to do so. Most wizards are not, ergo dragons are still a threat. Though they're not really that much of a threat given that they were used in a school tournament of all things. Worst comes to worst any adult wizard would be able to disapparate to safety in an instant.

Besides which, there's also the point that dragons are rare and fascinating creatures. The majority of wizards are both unlikely to ever run across a dragon and unlikely to want to kill one. If you look at dragons in the same way most people do hippos and rhinos you'll begin to see why. They're dangerous, sure, but we still keep them in zoos because we don't need to go out and slaughter them.

 

This is a fun thread. Thanks, OP et al., for the conversation.

I agree, esp. with Bellatrix at the end of OotP ("you have to mean it, Potter!"). This idea of intent seems to me to be a kind of inversion of what it takes to cast a Patronus. The Patronus Charm requires a happy memory but also the feeling of happiness, the desire to feel that way despite the depression the Dementors cause in people near them.

Your reading of the Unforgivables in DH goes with some of the ideas below by Aekiel and others that killing a dragon is perhaps not difficult with the Killing Curse but morally wrong. I wonder though if Harry's desperation to control the Death Eater and goblin in Gringotts and his momentary rage at Carrow when he attacks McGonagall shows that there is still intent and emotion involved, even if there isn't necessarily any training. Harry is an exceptional wizard, though, as his mastery of the Patronus charms show, so perhaps it isn't easy for everyone, but for a skilled enough wizard, the casting doesn't cause challenges in itself.

I like this idea and it goes with the role abstract concepts play in magical theory in HP. "Love" protects Harry, "happiness" defends against Dementors, and "death" (and "torture" and "mind control") willed and enacted against another person could work in the same way.

I want to push back against the idea that animals don't have souls in Harry Potter. I'm not sure this is true. In many of the books good, kind treatment of animals is an important virtue, in particular because of their intelligence and emotions. The murder of a unicorn is wrong; hippogriffs demand respect and curtesy; Crookshanks can recognize people who are trustworthy.

Also, Sirius says that as Padfoot he could keep his sanity, but not that he was completely overlooked by the Dementors. His emotions were simpler, but he still had emotions in the form of a dog, and the Dementors feed on that as well (not just souls through the Kiss).

Perhaps Dementors only feed on human souls because of their complexity and human souls sate them more than less complex animals' souls? (Or perhaps Dementors are like Ring Wraiths in LotR in the sense that they have a hominid shape and are cursed former humans who only hunt out human beings.)

I'm also thinking along the lines of Aristotle's de Anima (On the Soul), where he writes on the different senses and says that all living things have a soul (or psyche). In Greek, psyche doesn't mean "mind" as in the word "psychology", but means "soul" or in its earliest occurrences in Homer it means "life." For Aristotle, the most basic soul is the vegetal soul, the soul of being alive and striving to live. Even plants have this kind of soul. Animals that become more and more complex accrete different senses (touch is the most basic for Aristotle). Perhaps this is why Dementors only feed on human beings? Especially if the Killing Curse removes the soul (or psyche, life force) from body, and can kill animals (e.g. Hedwig in DH), this means that animals must have some kind of soul, even if simple and unappetizing to Dementors.

This reminds me of the HP/Avatar crossover fic, I think it's entitled Harry Potter: The Last Avatar (?), where Harry must kill the last dragon as part of the Triwizard Tournament. He finds it a disgusting form of bloodlust to kill such a magical creature. I think this response to the dragon is what would stay his (and other wizards') hands from killing magical creatures as well as human beings with the Killing Curse.

 

Considering the size restrictions based on power in the field of Transfiguration, it may be a dragon's size that prevents lower-level wizards from killing it. Moody mentioned how the 4th years couldn't kill him because they weren't powerful enough, but they may have been able to kill a rat or something within this size/power scale.

I agree with the idea that the AK makes a person dead, with all the effects of death happening as consequence. Thus, the soul separating from the body would be a mechanism of death rather than a mechanism of the killing curse. This also fits in well with how fawkes reacted to the killing curse.

Edit: The size restriction on the killing curse can also lead to interesting interactions with giants. If they are too big, even someone like Voldemort wouldn't be able to kill them with a killing curse. Instead, he would have to butcher them in smaller spatial quantities using dark magic.

You could even say a dragon's and giant's magical resistance is a function of their size and that magically they are often considered as whole entities; otherwise you'd be able to do things like accio a person's brain. I'm not sure how to feel about this concept of magical resistance though, as it may not play well with resistance to spells like the diffindo.

 

I really like the points your making, and agree with all of then in the context of Aristotles view of the soul. But, because I’m enjoying this conversation and learning things, I’m going to keep supporting my point just to see what you have to say.

If we follow the Stoics ideals, we can conclude that animals lack souls in their sense of the word. For the Stoics, the soul is the highest of three levels of pneuma, a word which means “breath.” The lowest kind of pneuma accounts for the cohesion and character of inanimate bodies (e.g., rocks); the intermediate kind, called natural pneuma, accounts for the vital functions characteristic of plant life. The soul, the third and highest level of pneuma, is responsible for things such as intellect, desire, and cognition. This creates an important distinction as the soul, rather then being a function of all life, is in this framework only a function of psychological and mental functions. Animals would not have a soul as they do not have complete access to their mental and psychological functions (e.g. a goose that migrates every year would not have the intellectual capacity to choose to not migrate. I understand that some animals can make tools, and some others show high levels of comprehension. Compared to humans, however, they lack a distinct level of psychological capacity.)

Therefore we could conclude that when a dementor is feeding it is on that third level of pneuma, the soul itself. It would explain why physically a person is still alive after a dementor feeds on them, and that dementors only feed on humans to get at the soul they have. The dementors consume that third level of pneuma

Furthermore, I would not classify Sirius in his animagus form as an animal. It is distinctly different as they retain enough conscious thought to make informed decisions, and are at their core, still human.

You list some reasons for why animals might have souls, as seen above, but I have another theory. They are magical creatures, and I believe magic is what explains their abilities. Across all magical creatures, a large portion of the animals are “normal” with a magical “ability.” For example, the kneazle. The more magical the creature, the greater the range of their magical abilities. For example, the dementor, or the unicorn.

@Polkiuj said that the Killing Curse, to paraphrase, makes things dead, And i totally agree. I think that’s the best explanation I’ve heard.

I understand that both of our ideas work in each proposed framework of the soul, so I guess at the end it’s whatever people want to choose.

 

Fun!

So I don't know Stoicism that well, only really recalling Seneca off the top of my head. I like the idea of the tiered pneumata because it makes the Dementor's effects even more specialized. So we have: pneuma 1) something like "matter" or "being" (since it includes rocks); 2) natural pneuma (akin to Aristotle's vegetal soul); and 3) soul, which includes cognition and desire. The Dementor's Kiss is deleterious, both destructive of and actually subtracting the human soul while leaving the more fundamental pneumata (1 and 2).

I'm glad that you mentioned intelligent animals in your comment because my first thought was "But, octopuses!" I still may disagree with the Stoic division of the soul because too simple. I would want something like an "animal soul" between the second and third pneumata because there needs to be some sort of rationale for motion if you are going to separate human from non-human animals based on the complexity of their thoughts, emotions, and psychology capacity as you said.

I'm reminded of Heidegger's example of the bee (I think in Being and Time?), which has a kind of language through dance and gestures (so, intelligent to an extent) and can find its way home from sources of food, but it does this through an animal drive or instinct as opposed to the level of human cognition. But the bee seems to me to be more complex than the what the natural pneuma accounts for. So perhaps we need another tier for animals in HP.

I wonder if, based on this model, Dementors still affect intelligent and emotional non-human animals, but they can only Kiss humans. I say this because elephants grieve their dead and even have a sort of ritual where they circle around a dead elephant, so elephants can definitely experience sadness and depression. They should be able to at least be affected by Dementors, but since they have no human soul, they can't be kissed.

To get back to the AK, I think our discussion of how human and animal souls work shows that the Killing Curse doesn't operate only by ejecting the soul from the body. If animals do not have human souls, and instead have a more basic soul common to all animals and plants, then the Avada Kedavra curse is not directed at the human soul, but at the body because it can kill Hedwig and the spider in GoF. It can't be directed at the most fundamental pneuma (1) of inanimate bodies because the Killing Curse doesn't destroy physical matter--apart from the exception of Voldemort's first fall, we're left with a corpse afterwards. Alternatively it could be directed at the natural pneuma (2), not specifically directed at the human soul, and thus destroy the animal's life. But at that point there seems to be little difference when we say AK causes bodily death or soul ejection. The body and animal soul would amount to the same thing at that point. Aristotle says the body is ensouled (empsychos), which is a nice way to think about how all living things have souls (no matter how basic) and they are integral to the body and sensation.

Yes, I agree that Animagi are human (see the thread on Animagus perception, it's pretty cool) and ultimately the Dementors can affect and sense Padfoot because Padfoot is Sirius. I think of Animagi in somewhat hybridized terms: Sirius is a dog-and-human at once when he transforms. But he himself says that the Dementors can still feel him but it is somewhat changed, which seems to imply to me that his emotions become more doglike and less complex, but still intelligible to Dementors, which may imply something about dogs' emotions. They woudn't be entirely invisible to Dementors even if their emotions aren't as complex and they aren't as intelligent as humans.

This is how unicorns work in Cauchy's Blood Crest (in the Dark Arts section of the Library). Without magic, unicorns can't live. Harry learns this through experience because he lives with a Dark wizard.

Since magic enables particular abilities, sensations, and intelligence in animals in HP, does magic complicate the structure of the soul as we've discussed? How would it do so? Or is it something else? The immediate problem would be how to deal with Muggles in such a system if we consider a "magical soul" part of a tiered system of soul and sensation. Obviously Muggles have human souls because they are human. They can sense Dementors and be Kissed by Dementors. But it would be interesting to see how soul and magic can be reconciled. In a fic this idea could be part of a pureblood rationale for wizard supremacy or a Grindelwald-style government.