Without the matter there is no duality. Without duality there is no experience. Without experience it is non-dual reality.

People never accept the universe is illusion it is because they are part and parcel of that illusion. The reality of the illusory universe often confuses people. 

Whatever thing remains eternal is true, and whatever is non-eternal is untrue. Since the world is created and destroyed, it is not true.

Truth is the thing which is unchanging. Since the world is changing, it is not true.

Whatever is independent of  form, space and time is true, and whatever has form,  space and time in itself is untrue.

Just as one sees dreams in sleep, he sees a kind of super-dream when he is waking. The world is compared to this conscious dream.

The universe is mere mirage created out of consciousness. Mirage cannot be true.

The universe is reality on the base of false entity (ego) within the false experience [waking].  The universe is an illusion on the standpoint the soul, which is the innermost self. The soul is in the form of formless consciousness.  This is because of some logical reasons. First analyze definition of Truth, and hence why the universe is not considered true.

 That is why Sri Sankara, indicated:-

63. Without causing the objective universe to vanish and without knowing the truth of the Self, how is one to achieve Liberation by the mere utterance of the word Brahman? — It would result merely in an effort of speech.

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.

Many indulge in mixing unimportant subject matter in Adyathmic or non-dualistic  discussion such as,  love, service to humanity,karma ,individualized God, religion.  love, service to humanity,karma ,individualized God, religion is noting to do with the soul, the innermost self because it is formless.    love, service to humanity,karma ,individualized God, religion are valuable only in the realm of duality therefore discussion about such matter in the Adyathmic discussion is waste of time. 

The wisdom consists in knowing the truth, that everything (mind or universe) is consciousness. Freedom (truth) is always there yet one does not know it.  But to those whose reason is turned away from physicality and who have attained the serenity of the soul, the innermost self (consciousness) are quite near to the ultimate truth or Brahman.  

That is why Sri Sankara, indicated  in Bhaja Govindam says: - [Jnana Viheena Sarva Mathena Bajathi na Muktim janma Shatena] - one without knowledge does not obtain liberation even in a hundred births, no matter which religious faith he follows.

To think once own body and his experience of the world is an illusion is difficult matter, unless one realizes the self is not physical but it is formless soul it is difficult to have glimpse of truth.

When one realizes the fact that, the self is not physical but the formless soul, naturally the body and universe becomes illusion.

The mind (universe) is emanating from soul (consciousness) means the mind is being effect from consciousness is not different from it. Deeper analysis shows it. Analysis needs deeper thinking and reasoning. Mind is whole universe thus it has a form. But where is the form in consciousness (soul) because consciousness is like an ocean and mind is like wave.  The universe is same consciousness, as the ocean produces the wave, so the consciousness produces the mind (universe).

The moment one knows the mind [universe] is consciousness, and then there is no ignorance. If one knows consciousness as self then everything is consciousness, the consciousness is second to none.  The mind is consciousness but due to ignorance one mistakes it for something else. One thinks the self is within the body; but the self is without the body and the world.

Mind ceases to exist without the matter. Without the matter mind ceases to exist as mind but it exists as matter- less awareness or consciousness. Without the mind neither the world nor its perceiver can exist.

Without the matter there is no duality. Without duality there is no experience. Without experience it is non-dual reality. Therefore, whatever prevails without the mind is ultimate reality.

The true nature of the soul (consciousness) is camouflaged by the waking experience ( illusion or duality).  To know the truth one has to discover and realize the formless substance of the mind or illusion. One has to learn to view and judge the worldview on the standpoint the formless soul as self.   Self-Knowledge is the prime goal of the truth seeker. This goal is hidden within the mind as its invisible substance and witness. Therefore, it is necessary inquiry, analyze and reason in to the nature of mind (duality or illusion) in order to unfold the mystery of mind or duality or illusion.

The person, who stamped their foot on the ground to refute to show the world, is real, ignore that in dream he would do exactly the same--stamp his dream foot on the ground and assert it to be real.