A functional complex in the psyche.
While Jung often used the word soul in its traditional theological sense, he strictly limited its psychological meaning.
I have been compelled, in my investigations into the structure of the unconscious, to make a conceptual distinction between soul and psyche. By psyche I understand the totality of all psychic processes, conscious as well as unconscious. By soul, on the other hand, I understand a clearly demarcated functional complex that can best be described as a "personality." ["Definitions," CW 6, par. 797]
With this understanding, Jung outlined partial manifestations of the soul in terms of anima/animus and persona. In his later writing on the transference, informed by his study of the alchemical opus-which Jung understood as psychologically analogous to the individuation process–he was more specific.
The "soul" which accrues to ego-consciousness during the opus has a feminine character in the man and a masculine character in a woman. His anima wants to reconcile and unite; her animus tries to discern and discriminate.["The Psychology of the Transference," CW 16, par. 522.]
The representation, in dreams or other products of the unconscious, of the inner personality, usually contra-sexual.
Wherever an impassioned, almost magical, relationship exists between the sexes, it is invariably a question of a projected soul-image. Since these relationships are very common, the soul must be unconscious just as frequently.["Definitions," CW 6, par. 809.]
The soul-image is a specific archetypal image produced by the unconscious, commonly experienced in projection onto a person of the opposite sex.
For an idealistic woman, a depraved man is often the bearer of the soul-image; hence the "saviour-fantasy" so frequent in such cases. The same thing happens with men, when the prostitute is surrounded with the halo of a soul crying for succour.[Ibid., par. 811.]
Where consciousness itself is identified with the soul, the soul-image is more likely to be an aspect of the persona.
In that event, the persona, being unconscious, will be projected on a person of the same sex, thus providing a foundation for many cases of open or latent homosexuality, and of father-transferences in men or mother-transferences in women. In such cases there is always a defective adaptation to external reality and a lack of relatedness, because identification with the soul produces an attitude predominantly oriented to the perception of inner processes.[Ibid., par. 809.]
Many relationships begin and initially thrive on the basis of projected soul-images. Inherently symbiotic, they often end badly.