Duality is illusory nature of the self and non-duality is real nature of the innermost self, which is consciousness.

People who argue there is nothing beyond the universe; there is nothing other than the matter; that the body was the man; and death was end of all.  According to them there is no truth other than the practical life within the practical world, which they hold as reality. Their only agenda is as long as they live in the world live happily with all the pleasant things of life, who can demonstrate that there is something left after the physical death.  Beg, borrow or steal – but live happily is their mantra.    

There are also people who believe strongly there was a sprit which defied the ravages of time, which cannot be confined in space; that sprit transcends the limits of this universe in which the body exists.  

How one can decide what is truth,   when he is bound by birth, life and death or form, time and space?  

The formless soul or  consciousness is the innermost self. And nature of the consciousness is formless and nondual.  One should realize the consciousness as whole universe without parts.  To describe nonduality as a system is erroneous because the dual and nondual is the nature of the self. Duality is illusory nature of the self and non-duality is real nature of the innermost self, which is consciousness.  Ultimate truth  cannot be confined into a narrow set of ideas.  

Chandogya Upanishads:-

This universe comes forth from Brahman and will return to Brahman. Verily, all is Brahman. A person is what his deep desire is. It is our deepest desire in this life that shapes the life to come. So let us direct our deepest desires to realize the Self. 

If one is seeking truth then it is necessary to bifurcate and drop the traditional Advaitic path which is not the means to self-knowledge and move ahead without the traditional baggage to get direct realization on his own as suggest by the great sages. 

Thus seeker of truth has to know what this universe? What is this ultimate truth or Brahman?  in order to realize the non-dualistic or Advaitic truth?   

No one can escape the waking experience which is the very basis of the physical existence. What was the waking experience before it appeared? Was their existence before the appearance of the waking experience?  When the waking perishes, does the soul or consciousness survive alone?  Is there a self or soul?  The seeker has to find answers for all these doubts in order to realize ‘what is truth’ and ‘what is untruth’.  

As one goes deeper in self-search one becomes aware of the fact that, the self is neither the waking entity not self is the dream entity but the self is formless substance and witness of the three states. And the formless substance and witness of the three states are one in essence. And that essence is consciousness.  If the formless substance and witness are one in essence, than there is second thing can exist, other than consciousness?  Thus consciousness alone is real and all else is mere illusion created out of consciousness, which is the innermost self. –FORMLESS PATH