Scio Occultus Res
The soul is still a mystery to mages. Most say that it is the part of a being that originates in the Supernal World, inhabits a body in the Mundane World, and returns to the Supernal World upon the death of the body. It is the part of the being that comes from above, the part that lends a spark of creativity and energy to the whole being. Unfortunately, using magic to examine a soul is a difficult concept, rather like an eye looking at itself. Magic can only observe the soul at a remove, through some intermediary, much the same way a mirror allows one to view a reflection of one’s own eye, rather than the eye itself.
What a soul is not is identity. There are incidents of soulless people, and their identity and sense of self are intact. What they lack is an empathy, a sense of connection to other people, and the ability to Awaken. Indeed, mages who have lost their souls lose their ability to do magic, though they remember when they could and how they did it. They just lack the spark of the Supernal that allows them to make use of the knowledge.
Souls can be lost, traded away, wounded, or killed; it’s just not easy. They can also be detached from the body to visit other realms – this is how mages are able to reach the Watchtowers in the Supernal World. The Abyss holds special dangers for souls, both because its energies are antithetical to Supernal energies and because the inhabitants of the Abyss often trade or consume souls.