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 universe in which we exist.+

Advaita and Dvaita are not some philosophies. Philosophers have made philosophy very complicated with their excessive analysis.

Manduka Upanishad has no assumptions whatever. It is an honest and bold inquiry into truth. It rises above scripture.

Manduka Upanishad:~Reality and illusion together make Brahman: nothing can be left out.

Manduka Upanishad:~ Atman is the highest Reality.

 Manduka Upanishad:~Only a few will be able to understand and assimilate it 

Manduka Upanishad is not meant for all, as it is based entirely on reasoning.

The essential message of Manduka Upanishad is that the whole world, that whatever is seen is only imagined. points out that even though it is harder for them, still women can attain Brahman just as men. Page 351

"From their notion": Everybody has his own imagination about facts and starts from that, instead of discarding his personal idea and looking at the fact. Page 333. V. 83 

Manduka Upanishad shows how one opinion may be used to contradict another, so that both may be thrown away. Opinions are not for philosophy; they are as Ashtavakra says, merely thoughts; it wants the truth.

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.

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.

Remember:~

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 universe in which we exist.

The world in which we exist is the dualistic illusion. The dualistic illusion appears as 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 as the waking or dream is the Soul, which is present in the form of consciousness.

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

In 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, the Self, which is present in the form of consciousness. 

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) discriminating between the dual (waking and dream) and nondual (deep sleep) experience with 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 Sruti 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 himself 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 for this idea of divine causality, and can, therefore, dispense with Shruti and arrive at the truth of Non-Dualism by pure reason. : ~Santthosh Kumaar