One of the fundamental concepts in the world of magic in Offetstine is the idea of living beings that can influence magic. These are beings which demonstrate some kind of sentience, sapience or self-awareness. While these ideas are not perfectly well-defined, they are usually found in the mundane natural world in humans and some other animals, and in the magical world in demi-humans, and they coincide with the presence of souls in these beings. The nature of souls is not well understood, and is considered part of philosophy more than it is a part of the science of magic, though certain schools of magic such as necromancy, which depends heavily on understanding the soul, have made strides in the understanding of the precise nature of souls.
It is not possible to define precisely what can and cannot have a soul, and there are many beings in the world which seem like they should have souls but do not, and vice versa. Parallels have been drawn between the idea of the soul and religious beliefs and philosophies such as creationism, though scholars of magic generally reject this idea. The existence of souls as a concept in magic does not imply that the world, before the prevalence of magic, did not form by entirely mundane means, and it does not imply any specific cosmogony.
Definitions
One general consensus about the definition of souls is that magic can only be controlled, employed and influenced by beings that have souls, though it is possible for a magically trained individual to create artifacts which influence magic of their own right, or through the Will of the People to make magical ideas real if they exist in the collective consciousness.
Protégé hypothesis
One hypothesis suggests that souls only exist to provide for magic, and the first beings to have souls were also the first beings capable of magic in any capacity, likely early humans or early animals. It suggests that humans, and some other early animals, were the protégés or champions of a then new concept that would eventually become magic, and to empower them in this new concept, these species developed souls per the Will of the People. Those souls conferred no benefit on their face other than the ability to control magic, but eventually that ability distinguished the branch of species from the others.
The hypothesis proposes that souls developed in this mundane species in order to provide them magic, because of their potential in reason, or some other factor that is usually associated with humans and other animals. The hypothesis does not specify what factor would have led humans and other animals to be able to control magic, though it has been understood by some theologians and others to mean that there is something about humans that makes them special and sets them apart from the rest of the world. Proponents of the hypothesis often insist that it is, by itself, religiously agnostic.
The hypothesis at first does not appear to line up with the age of other ethereal planes such as the afterlife and underworld. Some estimates suggest that these planes existed for anywhere from millions to billions of years before humanity. However, other ethereal planes are not necessarily made of traditional physical matter. The afterlife and underworld are instead made of incorporeal magical energy, which has a physical form that can be sensed and interacted with, but is not bound to any of the rules that physical matter is and operates under its own rules to a similar end result.
Magical energy is seen in the natural world as well, in the form of ethereal beings such as spirits and nymphs who exhibit various strange behaviors in the physical nature of their bodies. For example, while the conditions that a nymph of most subspecies is subject to may be explained by being made of biological matter, it is often impossible to dissect the body of a deceased nymph and identify those organs, or perhaps when injured, the damaged parts of their body may simply disappear in wisps. However, the level of apparent physicality of an ethereal object may vary. For other ethereal beings, for example, it is possible to take a swab of them and observe individual cells or molecules under a microscope. This implies that the afterlife and underworld were willed into existence through the minds of beings with souls, and appear to have the age they do because they are not physical in nature, and there is no conflict from the proposition that they are, in fact, young.
Heredity hypothesis
One interpretation of the concept suggests that there is nothing about the beings which have souls that entitle them to their souls, and instead, their heredity gives them their souls. The classification is convenient but not meaningful by itself, and suggests that it is simply a coincidence that living beings that are typically associated with higher-order reasoning, such as animals and humans, have souls. It is similar to the protégé hypothesis, but does not suggest that all beings which have souls share certain traits. Instead, it suggests that the family of beings that have souls follow a certain reproductive lineage which includes all animals.
The heredity hypothesis is generally more widely accepted by scholars than the protégé hypothesis. However, similar to the protégé hypothesis, it also has a significant number of religious interpretations that are not necessarily core to the hypothesis. Some interpretations suggest that the progenitor of souls and magic in the heredity hypothesis was a sexually reproducing eukaryote, often an early human, who had a child with god. These notions are widely disregarded in the community studying magic, though these interpretations, and variants of them, have served as the base for some extremist and radical organizations and cults.
Behavior
While a lot can be said about how to define souls, it is generally considered more productive by mages to focus on how souls impact the way the world, and magic, works. Generally, it can be said that many living beings in the world, including most animals, have a soul. That soul is created when they are conceived and exists until their death. As the study of souls is still in its infancy, many edge cases here are not well-understood, such as the presence of souls in children with anencephaly. Generally, it is understood that any being individually capable of becoming a mage has their own soul.
Generally, a being with a soul requires that soul to function as an individual, and some beings do not have physical forms on their own. A being may be only a soul and may possess another body or take an incorporeal, artificial form, and such beings are usually considered spirits. These beings often come from another ethereal plane, such as the afterlife or underworld. Sometimes, a being without a body can possess another body, which, if it has another soul in it, will usually push the soul out of the body, effectively killing the person but letting the body be used by the other soul.
Relation to cognition
Despite the implication of its name, the soul does not confer any powers of cognition by itself. For most souls of beings that have physical forms, the soul just provides a small amount of the character and personality of a person, the parts that aren't based on their species and the instincts and cognitive functions it provides. It is sometimes hypothesized that for spirits, the soul is responsible for all their cognitive function, but this claim is disputed. For some species of spirits that possess other bodies, they show only very generic and high-level cognitive function until they have a body to possess. For others, it is suspected that the magical energy around them, while it does not provide them a tangible form, does give them their cognitive power.
Moreover, the species of a being is likely not inherent to a soul since that species may change as a being is subjected to different magic, which implies that all traits which define a being's species are outside of their soul. The counter-hypothesis, which is considered more likely, is that all souls only provide that very basic high-level cognitive function. It suggests that the soul itself is not associated to any single species or any body, and that it can even be limited by being in a particular body, and is generally undetectable in mundane terms.
Death
Upon death, a soul departs from the host body and usually goes to the afterlife. However, there are some cases where the body might stay behind on its source plane, usually the natural world, to become a revenant. It is exceptionally difficult to continue to use a body after it has died, so the soul may wander the world on its own as a spirit if it is sufficiently powerful to resist going to the afterlife. Part of necromancy, for example, involves the preparation of bodies for accepting a soul again. A soul that has departed to the afterlife is widely considered to have reached its final destination. While souls are not subject to any conditions of spiritual death, especially the longer a soul has been in the afterlife, the harder it is to retrieve it from the afterlife. For a foreign soul to be in the afterlife, it is generally considered that the soul is "at peace," and it usually causes more problems than it solves to disturb the soul of a person who has died.
A soul in the afterlife is known to have some limited influence over the natural world and people who are still alive. For example, a soul still has a connection to the body it was alive in, and can still influence that body after its death. This connection to the natural world is closely leveraged by fields of magic such as necromancy, and has provided the most completely understood aspect of souls. It is generally understood that a soul, even after its death, emotionally reacts to events in its home plane (usually the natural world or underworld) and exerts some sort of subtle, but measurable, influence on those subjects. The influence is often understood as luck or blessings.