Many souls theory is religious theory based on false self (ego) within the false world.+

The Soul is the  Self. The Soul is present in the form of consciousness.  The Soul is the cause of the world in which you exist and it itself is uncaused.

Many souls' theory is a religious theory based on false self (ego) within the false world.  When the world in which we exist is created out of a single clay and that single clay is the Soul, which is present in the form of consciousness, the question of many souls does not arise. There is only one and only Soul, which is the cause of the universe. 

You are not the ‘Self’ because you are mortal.  You are mortal because you are bound by the experience of birth, life, death, and the world.  The ‘Self’ is the Soul, which is present in the form of the consciousness is immortal because it is ever formless, timeless, and spaceless existence. 

The one that is in ignorance is the Soul; the one that has to wake up from the sleep of ignorance is the Soul, the Self.

 The world in which you exist is the product of ignorance. When ignorance vanishes the world in which you exist is merely an illusion created out of consciousness. Without the illusion, the Soul, which is present in the form of consciousness alone will prevail as the ultimate reality or Brahman or God in truth.    Thus, the  Soul is the ultimate truth or  Brahman or God in truth.

Self-realization is necessary to realize ‘what is truth and ‘what is the untruth.

Many souls' theory is based on the false self and false experience(world). When the whole universe is created out of single stuff, which is the Soul then whatever the universe contains is also consciousness. Thus, the Soul is one, and in ignorance, the diversity appears as reality. 

Sage Sankara asks his opponents "How do you know there are separate individual Souls? Have you seen the Soul of a man? You can only say that you have seen different bodies. To say more is to misuse language. Therefore I call you liars unless you give proof, which is impossible.

Rig Veda: ~ The Atman is the cause; Atman is the support of all that exists in this universe.

So, it proves the Soul is not an individual but it is the support of all that exists in this universe.

The Soul is not limited to an individual. The individuals are many but the Soul is one. The individual exists within the universe. The Soul is the cause of the universe and it itself is uncaused.

The Soul is not within the human body. The universe is created out of single stuff. That single stuff is the Soul, which is present in the form of consciousness. Thus, whatever universe contains is bound to be the Soul, which is present in the form of consciousness.

In the dream world, the dream people appeared together and disappeared together. Similarly, the waking world and waking people appeared together and disappears together. Thus, the dream is created out of single stuff and that stuff is the Soul, which is present in the form of consciousness. In the same way, the waking experience also created out single stuff. And that single stuff is consciousness. 

The Soul, which is present in the form of consciousness is the cause of the three states and it itself is uncaused. The many soul theories are religious and yogic fables based on the false self (ego) and false experience (waking).

Knowledge of the single stuff is Self-knowledge or Brahma Gnana or Atma Gnana.

Like an ornament made from gold is Gold, which is born out of consciousness is consciousness. Like gold is the permanent thing, in ornaments made of gold, similarly, the mind, which is in the form of the universe is born out of consciousness, is consciousness in its essence.

Deeper Self-search reveals the fact that you are not the Self, the world in which you exist is the Soul, which is present in the form of consciousness, but consciousness is specifically not an entity or identity or a thing within the world in which you exist. But it is the cause of the world in which you exist and it itself is uncaused.

The Soul is hidden within the world in which you exist. The nature of the Soul is a formless, timeless, and spaceless existence.

Thus, it is necessary to realize the world in which you exist is created out of single stuff, which is consciousness. The consciousness is the ultimate truth or Brahman or God in truth. 

Thus, God alone is real; the world in which you exist is merely an illusion created out of consciousness.

“It takes time for the seeker to gain the perfect understanding of ‘what is the truth’ and ‘’what is untruth’. It takes time for the Soul, the Self to wake up from the sleep of ignorance, and it takes time for one realizes the truth, which is beyond the illusory form, time, and space.: ~Santthosh Kumaar