In spiritual life, the basic distinction or separation is the soul from God. That separation is reflected in psychological and physical mediums when the soul incarnates. At the outset of incarnation, the separate soul, when first entering into these planes, does not experience, either psychologically or physically any differentiation from the environment around it. Specifically, the environment of the Mother.
The earliest psychological learning is the development of a separate psychological and physical entity; this learning takes place during the first six months of life. The foundation created is non-verbal and non-conceptual, except in the most rudimentary sense. The soul is then going from undifferentiated matter, physical and psychological, to differentiated matter, physical and psychological.
When the soul seeks liberation during its lifetime, part of the process is extricating itself from the attachment to identification as a separate physical entity, which means merging back into matter on the physical and psychological plane so that only the soul is once again separate.