Advaita is the proof of the existence because the dvaita hides the proof.+

Swami Vivekananda: ~ “Advaita encompasses everything. Since Advaita requires heavy-duty intellectualism, it had to be progressively simplified.

Advaita is proof of existence because the dvaita hides the proof. Advaita is universal. Advaita is the nature of the Soul, the Self. The world in which you exist is created out of single stuff. That single stuff is consciousness. Knowledge of the single stuff is Advaitic wisdom. 

Advaitic truth is very simple, but it is very difficult to realize because you have accumulated mental garbage from different sources in the name of Advaita. Until you discard all the accumulated knowledge you will never be able to realize the Advaitic truth, which is beyond the form, time, and space. 

The Advaita is the nature of the Soul, the 'Self' shines on its own awareness when wisdom dawns. 

Upanishad:~ ‘They alone in this world are endowed with the highest wisdom who are firm in their conviction of the sameness and birthlessness of Atman. The ordinary man does not understand their way. (Chapter IV — Alatasanti Prakarana 95-P-188 in Upanishads by Nikilanada)

Remember:~

The Advaita is the Soul is the cause and the support of all that exists as the world in which we exist.

The Advaita is present in the form of consciousness. Advaita is the root element of the universe. From the Advaita, the universe comes into existence. In the Advaita, the universe resides. And into the Advaita, the universe is dissolved. The Advaita is the parent of all that is there is.

Do not believe in a thing because you have read about it in a book. Do not believe in a thing because a wise man has said it was true. Do not believe in words because they are hallowed by dualistic knowledge Find out the truth for yourself. Use Soulcentric reason, which leads to the realization of the truth, which is beyond form, time, and space.

Advaitic can never be reached by argument and provocation. Discard all the accumulated dualistic knowledge by realizing the world in which you exist, exists because of ignorance. Get rid of the ignorance by realizing the world in which you exist is created out of single clay and that single clay is the Soul, which is present in the form of the consciousness. Realizing the ‘Self’’ is not you but the Soul is Self-realization. The Soul is the cause of the universe and it itself is uncaused.

That is why Sage Sankara says: - VC-65_As a treasure hidden underground requires (for its extraction) competent instruction, excavation, the removal of stones and other such things lying above it and (finally) grasping, but never comes out by being (merely) called out by name, so the transparent Truth of the Self, which is hidden by Maya and its effects, is to be attained through the instructions of a knower of Brahman, followed by reflection, meditation and so forth, but not through perverted arguments.

People dwelling in darkness, but thinking themselves wise and erudite, holding ‘I’-centric gurus and their teaching as final become blind to the Advaita because of their dualistic intelligence. They think what they know as the ultimate truth.

They think whatever they propagate is the ultimate truth. The question never occurs to them, “Is what I know is really the truth?:

Until the scientists become the seeker of the truth of their existence, the truth will not reveal. The truth of the whole cannot be got under the microscope. When all their invention fails to yield truth they have to use their reason to reach the ultimate core of their existence.

Lord Krishna confesses that the oldest wisdom of India (our true Advaitic wisdom) has been lost: people misinterpret and falsify it today as they did then. It is not yoga but the philosophic truth. But nobody knows it. The teachers of philosophy and leaders of mysticism or religion do not want to inquire into truth and have no time for it. (Gita –Chap- IV-v.2)

In Gita Chap.IV where Lord Krishna says: ~ "This yoga has been lost for ages" the word yoga refers to Gnana yoga, not other yogas: the force of the word this is to point this out.

Lord Krishna describes some of the other yogas but devotes this chapter separately to Gnana Yoga. So one sees even in those ancient days people did not care for Advaita; they wanted religion; hence Gnana got lost. That is why Krishna calls it "the supreme secret." 

The man who possesses the highest intellect can grasp Advaita, by merely hearing the truth mentioned will know it.:~ Santthosh Kumaar