Katha Upanishad says:~ Fools dwelling in darkness, but thinking themselves wise and erudite, go round and round, by various tortuous paths, like the blind led by the blind. (Ch~ II-5 P-14)
Those who indulge in the perverted argument on their own standpoint and opinion are not seeking the truth, which is beyond form, time and space. They just want to exhibit their accumulated knowledge accumulated from here and there. They think what they know is 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?
Instead of finding fault and arguing on unimportant subject matters, the seeker has to investigate the truth about the ‘I’ which appears and disappears.
An honest introspection will reveal the truth, which is beyond the ‘I'. The ‘I’ is bound by the form, time and space. Those who are stuck up with ‘I’ will never be able to drop their accumulated knowledge based on the ‘I’ or ‘I AM’.
The ‘I’ know attitudes blocks the realization of the truth, which beyond the form, time and space.
The seekers egocentric attitude blocks him from accepting the truth other than his accumulated knowledge from here and there. The seeker has to develop the Soulcentric attitude and by rectifying his reasoning base from ‘I’ to ‘I –LESS’ base will change his perception of the world in which he exists.
Arguing with religious believers is fruitless. Belief in tradition and the scripture as if they were true or factual quite clearly is delusion, but the payoff for holding such delusions is, for those who hold them, extremely compelling ~ the avoidance of the "wrath of God," the hope of heaven or salvation, or the imagined "end of suffering."
That is why Sage Sri, Sankara:~ VC- 61. For one who has been bitten by the serpent of Ignorance, the only remedy is the knowledge of Brahman. Of what avail are the Vedas and (other) Scriptures, Mantras (sacred formulae) and medicines to such a one?
The Soul is the ultimate Truth or Brahman. The Soul is in the form of the consciousness. The Soul is the Self -evident. It is not established by extraneous proofs. It is not possible to deny the Soul because it is the very essence of the one who denies it. The Soul is the basis of all kinds of knowledge, presuppositions and proofs. The Soul, which is present in the form of the consciousness (spirit), is ultimate truth or Brahman. The Brahman is God.
What is existence, nonexistence, unity or duality? What need us there to say more? Nothing from the Soul because whatever seems to emanate from it, is non-different from itself. There is no second thing other than the Soul, which is present in the form of the consciousness. One should not mistake Self (Soul) for the ‘I’.
Those who assert the world is a reality, are still in elementary stages of the preliminary analysis. The world is a reality within the waking experience, but the waking experience is mere an illusion. The same way the dream world was a reality within the dream experience. The dream became unreal when the waking took place. Same way the waking becomes unreal when Advaitic wisdom dawns.