In many fantasy campaign settings good, evil, law and chaos exist as literal and tangible things. They are forces of nature and exist similar to elements like water or earth. In this framework, an angel is better thought of as a "goodness elemental" rather than a race or species, like those that can become PCs. This is, as far as I can tell, a pretty common explanation for retaining alignment and it is a very good one that allows for nuance when it comes to the choices made by PCs.
For Aimsir, however, the metaphysics of magic I settled on early in the process made this framework... insufficient. While good, evil, law and chaos still exist as tangible forces in Aimsir, and certain outsiders are living manifestations of their alignment, it works different for most people. In Aimsir, magic is the direct byproduct of consciousness. As such, it is directly tied into the ability of creatures to think, make choices, and take moral agency for their actions. This brought into focus a problem I've had for a long time with certain spells being "always good" or "always evil" within the rules as written.
Take, for example, Symbol of Pain which bears the [evil] descriptor. Rules as written this means a cleric of a good god can't even prepare this spell and that casting it is an inherently evil act. Okay, causing excruciating pain to living things is usually wrong (and, in some cases may even rise to the level of torture, a clearly evil act) so that might make sense. However, Symbol of Death, which...y'know... kills people, does not have the [evil] descriptor and thus can be prepared by a good cleric. What?
Let's imagine a scenario that a player in an Aimsir game might experience. A Cleric of Vindex (the LG Saint of Justice)and her companions are riding past a village, only to see a terrified trow running from your standard-issue mob of peasants with torches and pitchforks. When the cleric asks why the mob is pursuing the trow, their leader explains that they think he is a warlock who cursed their most recent crop. The trow professes innocence and claims that the village has singled him out due to anti-trow bigotry. The cleric, in accordance with Vindex's teachings, declares that the trow's guilt should be determined at a fair trial and that she will not permit the crowd to simply kill him. The crowd disagrees and moves to attack the party.
As written, if the cleric were to cast Symbol of Pain in the direction of the mob, causing them intense agony, but also disabling them and possibly taking them out of the fight entirely, she would be committing an inherently evil act. Her patron probably wouldn't even have granted her the spell in the first place. But her patron would allow her to prepare and cast Symbol of Death killing some of (or perhaps even all) of the peasants, and that would not be inherently evil (though it may still be ruled an evil act by the GM). This flies in the face of how most people I know understand morality.
Instead, in Aimsir, the vast majority of spells do not have an alignment descriptor. Some still do: summoning an evil outsider as a servitor is still a big no-no, as are any spells that explicitly require the sacrifice of a sapient creature. But most spells will depend on the context of the action and the judgment of GMs.
So go ahead and use Animate Dead to fight off the zombie hordes with some undead of your own or cast Protection from Good to buy yourself time to explain to the paladin that he's got you confused for your story's villain. Unless you're literally an angel or a demon, good and evil in Aimsir is a thing you do, not a thing you are.