Chandogya Upanishad: ~ sarvam khalvidam brahma - All this (universe) is verily Brahman(consciousness).+

Sage Goudpada: ~ To establish the truth of Non-duality by sheer reasoning alone. He begins by defining "What is real?" "What is unreal?" etc, because that is the right way to understand and assimilate. People must first know what they are talking about. (Manduka Karika)

Sage Goudapada quotes from the Upanishads: ~ "There's no plurality here"; "The Soul  appears to be many"; "those who are attached to the creation or production or origination go to utter darkness," and "the unborn is never reborn, for what can produce it?”

Sage Goudapada’s rational exposition of Advaita:~ Whatever is seen, whether external or internal, whether by the ordinary persons or yogis, is unreal.

The whole objective universe is non-real. Your existence is a reality within the unreal world.

Just as rainwater falling on a mountain peak runs down the rocks in all directions, even so, is the dispersed who sees only the diversity and manyness of the world and does not grasp the Oneness of the Soul, which is present in the form of the consciousness. The nature of the Soul is the fullness of consciousness.

As pure water poured into pure water becomes one with it, so also the one who knows ‘Self is not ‘I’ but the ‘Self’ is the Soul, which is present in the form of the consciousness become one with the Soul, which is present in the form of the consciousness along with the world in which he exists.

He who realizes Soul as the 'Self' liberated from the bonds of ignorance, becomes free from experiencing the illusory form, time, and space as a reality.

A Gnani’s attention is fixed on the Soul. He is free of ignorance. He is in solitude in the midst of the dualistic illusion. His quest is over. He has reached the highest goal.

When the Soul is mentally separated from the illusion by realizing the illusion too is nothing but consciousness then there is no second thing that exists other than consciousness.

Chandogya Upanishad: ~ sarvam khalvidam brahma - All this (universe) is verily Brahman. By following back all of the relative appearances in the world, we eventually return to that from which it is all manifest – the non-dual reality.

Then it is no use going a roundabout way, trace the Brahman which is the formless substance, and witness of the universe, which is in the form of the mind. By tracing the source of the mind or universe one will be able to realize the Brahman.:~Santthosh Kumaar