There has been innumerable doctrinal discussions concerning the separation between the body, the spirit and the soul. I cannot at the moment recall the first time the church decided to identify the three separate parts of a human, but I can tell you that one Valentius, an early Gnostic (mid second century) was the first to propose the triple nature of man; body (known as soma), soul (psyche) and spirit (pneuma). (it should be mentioned that St. Paul makes the same division earlier without elaborating) his division is of course not exactly according to doctrine (seeing as he was both a Gnostic and also some 200 hundred years before the Cult of Mithra was incorporated into Christianity), but his views are still the basis for all later discussions on Spirit-Seed and Angel Christ.
Soma: (being our physical form) controls the animal urges, as well as instincts and base fears. It is the intriscinctly "evil" part of man. (Gnosticism defines the world as a creation of the devil, not god.)
Psyche: the so-called "immortal soul" which, after death, resides in what we could call Purgatory, it will there be purified (much like the burning away of sins we now have, only without the burning) to finally be able to be resurrected. It is not entirely certain what he meant by this, because he also says that true resurrection can only happen at the end of time. (not the End of Ages as we had some years ago). The Soul carries memories, thoughts and the personality. This is the bit that Hermetic magic cannot touch.
Pneuma: Every person possess something known as the spirit seed; Sperma Pneumatikon, which can combine or merge with the Pneuma (here, and later, defined as/equated with Angel Christ) itself, thus upon death enabling it to return to its source; true resurrection. If the Sperma Pneumaticon merges with the Pneuma it is free of this world. I would guess that when a person dies without having fulfilled said potential, they become a ghost. Thus, as the Soul is the true bearer of memories and emotions, a ghost is naught but a pale copy of the true original.
Sorry for the extremely incoherent rant here, am a bit tired.
Hope it's at least a bit enlightening.
Personally I'd say that Soma is controlled by Corpus and Mentem, while Pneuma is controlled by Mentem alone and Psyche cannot in any way be affected. Thus changing a persons emotions conflicts with Essential Nature, and in effect making any change temporary, exactly like with shapechanging.
Just my two Aureus...