Advaita (non-duality) is the real nature of the Soul, the Self. The dvaita (duality) is the illusory nature of the Soul, the Self.+

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)

Existence is nondual. Nonduality cannot be described through words for all uses of language fail to express it. Nonduality is sought to be indicated by mentally negation of duality (all attributes and characteristics).

Sage Sankara says:~ How can the talk of diversity, dvaita, apply to the Supreme Reality which is one and homogeneous, Advaita? Who has ever observed diversity, dvaita, in the unmixed bliss of the state of profound sleep?

Advaita (non-duality) and the dvaita (duality) are the nature of the Soul, the innermost Self. It is not some intellectual theory. Advaita is the real nature of the Soul and the dvaita is the illusory nature of the Soul.

Advaitins believe the Atman (Soul) is Brahman, and the world is an illusion.

Dvaitins believe the body as the Self, they believe the world is a reality, and they believe in creator and creation theory.

In India, Advaita and Dvaita are merely a religious tradition, which they inherited from their ancestors. No one questions their validity because it is considered blasphemy to question any Guru and God-men or pundits.

Remember:~

Advaita and Dvaita are not some philosophies. Advaita is the nature of the Soul, which is present in the form of consciousness. Dvaita is the illusory nature of the Soul, which is present in the form of the world in which we exist.

The world in which we exist is a dualistic illusion. The dualistic illusion appears as a waking or dream (dvaita) and disappears as deep sleep (Advaita)

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

The one that transcends the waking or dream is the Soul, which is present in the form of consciousness.

One that remains without waking or dreaming in deep sleep is the Soul, which is present in the form of consciousness.

In a deep sleep, the Soul remains in its own true nature so it is in Advaitic mode.

In waking or dream the Soul is in the dvaitic mode.

The one that becomes dvaita and one that becomes Advaita is the Soul, which is present in the form of consciousness.

Thus, whatever becomes dvaita (waking or dream) and Advaita (deep sleep) is nothing but the Soul.

From the standpoint of the Soul, the dvaita (duality) is an illusion. In reality, nothing ever existed; nothing exists and nothing ever exists at any point in time because the dualistic illusion has no value.

Thus, the Soul, the Advaita is real and eternal.

Sage Sankara says: ~ VC- How can the talk of diversity, dvaita, apply to the Supreme Reality which is one and homogeneous, Advaita? Who has ever observed diversity, dvaita, in the unmixed bliss of the state of profound sleep?

If a waking entity (you) discriminates between the dual (waking and dream) and nondual (deep sleep) experience by constantly reflecting, then the egocentricity destroyed the Soul-centricity will be established.

It is possible to show the unreality of the three states even from Soulcentric reasoning by a perfect understanding of ‘what is what”.

Without recognizing the authority of the scriptures, one can prove the Advaitic truth through reason alone.

Sage Sankara founded his Advaita Vedanta either on reason independent of Sruti or on Shruti confirmed by reason."

Sage Sankara's commentary on the Mandukya Upanishad, II, 1: This (the unreality of duality) is borne out by the Srutis ... But it is possible also to show the unreality of the object world even from pure reasoning, and this second chapter is undertaken for that purpose.

Sage Sankara had often said that his philosophy was based on Sruti, or revealed scripture. This may be because Sage Sankara addressed the ordinary man, who finds security in the idea of causality and thus in the idea of God—and Revelation is indispensable to prove the latter. He believed that those of superior intelligence, have no need of this idea of divine causality, and can, therefore, dispense with Shruti and arrive at the truth of Non-Dualism by pure reason. : ~ Santthosh Kumaar