HPMOR

According to Eliezer himself, learning the Patronus Charm 2.0 makes you unable to cast any version of the Killing Curse, whereas learning the Killing Curse 2.0 makes you unable to cast any variant of the Patronus Charm. It means that there are three mutually exclusive states of mind a person can have regarding those spells:

• A person believes that Death can and should be defeated, enabling them to cast the True Patronus Charm. They cannot summon a regular Patronus, since they aren't capable of ignoring Death, and they cannot hate somebody enough to want them dead for the sake of it, much less not care about their life or death. The only people who ever unlocked such a state of mind are Harry, Hermione and maybe Godric Gryffindoor - the details are sort of unclear.

• A person does not consider Death to be their enemy, but they still care about their fellow sentients. They can cast both a Patronus Charm and the Killing Curse given the right training and magical power, but the improved variants remain locked to them. Most wizards seem to fall under this category, though few can use both spells due to how tough they are to learn.

• A person is apathetic enough regarding the lives of others for them to cast the True Killing Curse through their apathy. They cannot summon any Patronus, since they don't want Death defeated and cannot bring themselves to be happy and they have no reason to cast the basic Killing Curse, assuming they are even capable of doing so. Dark Evangel and Tom Riddle are likely the only ones who managed to weaponize such an attitude, though there are probably more people who think like that.

There are of course other, 'inferior' states of mind, such as being capable of happiness but not of murderous hatred - Dumbledore - or being utterly hateful and unhappy - most Slytherins - but let's focus on these three. My questions on the topic are:

• Can a person switch between these states of mind? As in, what if I hated somebody enough to want them dead for the sake of being dead because they did something awful to me, but after some therapy I learned the value of forgiveness and became a transhumanist who wished to give everyone immortality? Or what if I learned that there was indeed a way to defeat Death and it caused me to desire immortality for everyone, but then obliviated that memory and became able to ignore Death once more? If something like that is possible, then I say there's a good chance for Harry to learn the Killing Curse after all, especially with his 'Dark Side' in play. If not, then that means that Harry's endeavor to teach Voldemort love and happiness is doomed to fail by default.

• Is it possible for these ideologies to have reasonable exceptions? If I was a True Patronus caster, would that make me obligated to try and save everyone, regardless of what they themselves wanted? Would I need to save the Sorting Hat, even though it only wanted to die? (I suspect the answer is no, since Harry was willing to let the Hat be destoyed, but he had multiple reasons for it). What if I was deeply concerned about everyone's lives, but was also hopelessly suicidal and desired immortality for everyone but myself? Conversely, if I was absolutely selfless and cared about any life other than my own, would I be able to cast the True Killing Curse on myself?

• Bonus question: Which variant do you find most useful, all other things being equal? Assuming that there are no clever tricks to bypass the mutual exclusivety and that you would keep pursuing your current ideals regardless of what ideology you chose, would you rather be able to cast the True Patronus Charm, the True Killing Curse or the vanilla versions?