Chandogya Upanishad: ~ “Whoever sees the Self in all does not see death, disease, or diversity. 

The Self is the invisible and unborn Soul hidden by the ‘I’.

The ‘I’ is present in the form of the mind; therefore, ‘I’ is the mind.

The mind is present in the form of form, time, and space.

The form, time, and space together are the mind.

The duality is present only when the form, time, and space are present; therefore, the form, time, and space together are the duality.

The form, time, and space are present in the form of the universe; therefore, the form, time, and space together are the universe.

The universe appears as the waking or dream; therefore, the waking or dream is the universe.

The waking is a parallel dream, and the dream is a parallel waking.

That is why Bhagavad Gita: ~ “The permanent is always there, only the transient ‘I’ comes and goes. (2.18)

The ‘I’ hides the invisible Soul, the Self, which is unborn, eternal.

People think the ‘I’ without the body is the Self. The seeker has to realize that ‘I’ is not the Self, but the invisible Soul, which is the cause of the ‘I’, is the true Self. The invisible Soul is nondual, which is eternal.:~Santthosh Kumaar