This is my own theory describing what I recognize as the Soul. This theory is distilled from my study and observation of; Psychological theories for inner work such as Active Imagination and Dream Analysis, mythology from various religious or esoteric texts and especially the deeper meanings hidden within, and altered states of consciousness achieved through meditation, breath work, thought manipulation, and a host of others methods. I will be describing these in much more detail as a part of my ongoing writings, but for now I will continue with the big picture view of my theory.
The Psyche, a common term in the fields of psychology and psychiatry, is not one's Consciousness. The Psyche is better described as an inner world. Though you may not be aware of it yet, this inner world is where the majority of one's thoughts come from unless consistently focused. This inner world is vast and also explorable. This world is where one's Soul can be found.
The Soul also carries with it a destiny or some sort of core desire(s) which drive a person to do be who they are. One's Psyche contains many different distinct entities within it that can also effect one's thoughts and therefore, their actions.
A Psychologist would observe this by identifying some sort of abnormal behaviour, or a pattern of negative behaviour in their patient. Once identified, they travel the patients memories back through time and go down to a core point in history where the significant event occurred which led to the behaviour. They go right up to the border of the psyche and communicate to those within the psyche to bring balance back to the patient and their Inner World. Various states of Hypnosis also work on this same general method.
Powerful psychedelics could be thought of as vehicles which carry a person's consciousness through that barrier of the physical body (which is where my consciousness normally resides) and into the Psyche. Certain Meditations can also be used to either approach the barrier and communicate directly with what is within, or enter if the necessary understanding and action is known.
The more focused and purposeful a person is, the deeper one's happiness and vitality, the more of their own Soul they are expressing. The more one acts with certain virtues such as understanding, love, & honesty in their daily life, the more Soul can come into the physical world. On the other end of the spectrum, the more inner conflict and unresolved trauma, the more diluted the Soul's influence is on a persons life.
Good evidence for this general model being accurate is the instruction given in all religion and mystery traditions to act in certain Virtuous ways. Great evidence for this general model is seen when one can identify the deeper levels of meaning and patterns within the religion or tradition. All of them have stories of entering altered states of consciousness to gain knowledge. All of them contain lessons on confronting fears to achieve spiritual reward. The best evidence for the accuracy of this idea of the Soul I describe can only be obtained by traveling inwards and learning how to identify the barrier of your own psyche and the origins of the thoughts that come through.