Answer: Development of the soul happens within a very narrow and precise framework, when a person is included in a group and begins to develop the characteristic of bestowal along with the members of the group until reaching the characteristic of love. His involvement with this develops the soul. A soul cannot exist in one person, only in a collection of people.
The most optimal situation is when ten people gather and through the correct use of the ego, between themselves they begin to build over-egoistic properties of connection above it. I emphasize: over-egoistic that is the opposite of egoism by using it in the opposite direction.
When they use it this way, in the opposite direction, a very interesting phenomenon happens among them. To the extent of their effort, not through suppression of the ego but through using it correctly, they create a property of love and connection above it.
They begin to feel that they lack the power that will help them rise above the egoism and use it correctly. They get this power from the depths of creation. In the unity between them, they suddenly discover a force in the center of the connection between them, like a whirlpool begins to be disclosed between them. But it doesn’t draw inward, instead it emits outwardly, and the Upper Light, the power of bestowal, reciprocal connection, love, goodness, and cooperation rise up from there.
When that force completes the correct connection between them and fills them, then the common state they attain is called a soul.
From the Kabbalah Lesson in Russian 6/9/16