The non-dualistic or Advaitic truth has to be grasped and realized in the midst of the waking experience. That is, being aware of the truth and untruth, reality and unreality. And able establish himself in the truth and able to view and judge, the three states, on the base of the soul, which is ultimate truth or Brahman.
It is unfortunate people are stuck with their accumulated ideas based on the false self, and imagine about non duality and say nothing exist other than the source. But a Gnani says everything exists (illusion) but everything is created out of the consciousness. Everything arises from the consciousness, and subsides as consciousness. Thus, the whole diversity (three states) has no relevance, on the standpoint of the formless soul , the innermost self.
Everything (illusion) is nothinness (consciousness) realizing the three states are created out nothingness (Consciousness). Nothingness is the nature of the consciousness, because there is no second thing exists other than itself.
Those who lack the intelligence to discriminate between formless witness [subject] and three states (object) will not be able to grasp what is real and what is unreal. Both subject and object are consciousness, not subject alone.
The truth can never change. The nature of truth is, it can never be changed under any circumstances. It may be misrepresented. It must apply to the whole of existence, to the whole of the universe. It is in the object (three states) alone that one has all changes, as deeper analysis points out.
The subject [formless witness] remains unchanged. The subject [formless witness], as such remains immortal. It can never die for it never changes. The body and the world are an object, and goes, but the subject or the knower of the body and the universe, can never go. The seeker has to take this principle as his guiding thread and non-dual truth becomes easy to grasp. The formless witness can never be subject to the changes of the object; it is unchanged. The mistake usually made is that subject becomes object, or that object is subject.
If one wants to have an absence of contradictions, absence of duality, there must be one entity, one being. If one has experience which is an object [mind], there is a contradiction between subject and object, for "mind” is an object.
The duality is reality on the standpoint of the false self (ego or body as Self). The duality is a mere mirage on the base of the true self, which is formless consciousness. This understanding comes only to the serious seeker, who has a real urge to know the ultimate truth, which is beyond the all the teachings and teachers. There is neither teaching, nor teacher, nor student in the realm of truth.
Different paths will not converge to the same Ultimate Reality because they are based on the false self. They are not the different stages in the same path. People fight about the differences and the greatness of their chosen paths but only through wisdom one can realize the Ultimate Reality.
One has to have perfect understanding and march ahead, surely and steadily, towards that Ultimate Reality, which is consciousness or Brahman or Christ or Buddha. One becomes limited to the concepts, names and forms within the waking or dream. Waking or dream originates from the soul.
The soul is the true self. The soul is in the form of consciousness. Realizing the consciousness as the true self is truth realization. Consciousness is formless, limitless, permanent and unchanging, and by its nature non-dual and universal. The consciousness is the formless knower of the mirage (universe) which comes and goes.
Realize Brahman or ultimate truth here and now, in this very life , not in the next life and in the next world by realizing the fact that this life itself is an illusion.