Mundaka Upanishad:~ As rivers flow into the sea and in so doing lose name and form, so even the wise man, freed from name and form, attains the Supreme Being, the Self-luminous, the Infinite. He who knows Brahman becomes Brahman.+

When the river merges with the ocean then it losses its identity. When the dualistic universe merges with consciousness then there is nondualistic reality.

Manduka Upanishad:~ Objects do not disappear, they are there, and yet they are non-dual. Disillusionment is not the same as appearance. Page 74. v. 17

Look into the nature of the universe. And you will be able to see that universe by its very nature is illusory. The moment you understand that the universe is illusory, ignorance disappears and Self-awareness arises.

Mundaka Upanishad:~ As rivers flow into the sea and in so doing lose name and form, so even the wise man, freed from name and form, attains the Supreme Being, the Self-luminous, the Infinite. He who knows Brahman becomes Brahman. ~ 3.2.8-

Self-awareness is the state of non-dual reality. That is the state of Advaita.

People never realize non-dualistic awareness through religion and yoga.

Self-awareness raises only by mentally transcending the dualistic illusion into non-dualistic reality.

Manduka Upanishad: ~ Whoever distinguishes between a cause and an effect is a dualist, even whether he says the world came from nothing or from something. (p.251)

Existence cannot be a cause and effect at the same time, from the point of view of the dualists, but deeper Self-search shows the Existent is no-two and causality can’t rise at all.

The real existence is formless, timeless, and spaceless existence. the form, time, and space are merely an illusory existence.

Sage Goudapada quotes from the Upanishads: ~ "There's no plurality here"; "The Soul through its powers appears to be many"; "those who are attached to the creation or production or origination go to utter darkness"; "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.

Thus, whatever you have seen, known, believed, and experienced as a person within the waking experience is bound to be an illusion created out of consciousness. Thus, the Soul, which is present in the form of consciousness alone, is real and eternal.

Consciousness is ever-present. Without consciousness, the world, in which you exist ceases to exist. Consciousness is Self-evident. It is not established by extraneous proofs. It is not possible to deny consciousness, because it is the very essence of the one who denies it. Consciousness is the basis of all kinds of knowledge, presuppositions, and proofs. Consciousness is everything. Thus, consciousness is the ultimate truth or Brahman or God in truth.

Remember:~

The cause and effect are possible only in the domain of form, time, and space. therefore the cause and effect is part of the dualistic illusion or Maya.

In non-dualistic reality, there is no duality. The dualistic theory says that whatever was in the cause was also in the effect. They say that the gold brick, the gold medal, the gold ornaments --are in the seed--the gold. Deeper Self-search reveals the fact that, if cause and effect are one what is the difference between the two?

The nature of the Soul is a silent, featureless one without attributes. The Soul, which is present in the form of consciousness, is not an object but is always the subject.

The truth is beyond form, time, and space. Self-knowledge or Brahma Gnana or Atma Gnana dispels ‘Ignorance’.

The Self is the Soul. The Soul is present in the form of consciousness; there the object has become one with the subject. there is only unity in diversity.

Consciousness is the ultimate truth or Brahman. Consciousness is ‘the one without a second’, the one which alone exists as the ultimate reality.

Sage Sankara’s Supreme Brahman is impersonal, Nirguna (without Gunas or attributes), Nirakara (formless), Nirvisesha (without special characteristics), immutable, eternal, and Akarta (non-agent). It is above all needs and desires. It is always the Witnessing Subject. It can never become an object as it is beyond the reach of the senses. Brahman is non-dual, one without a second. It has no other beside it. It is destitute of difference, either external or internal. Brahman cannot be described because the description implies a distinction. Brahman cannot be distinguished from any other than It. In Brahman, there is not a distinction between substance and attribute. Sat-Chit-Ananda constitutes the very essence or Svarupa of Brahman, and not just Its attributes. The Nirguna Brahman of Sage Sankara is impersonal.

The Soul remains in its own awareness. The illusion (mind) does not merge with the Soul because it never really separated from it. The Soul remains the one without a second (Advaita). The Soul’s separation is an illusion, the result of ignorance which when dispelled, the hidden reality shines as formless, timeless, and spaceless existence. :~Santthosh Kumaar