Why does Adi shankaracharya think that self cannot perceive a relation between itself and avidya?
Let's just consider that you are in the state of dream -
It is not indeed possible for you to perceive your Self as related to dream, at the same moment (that your Self cognises dream); for, the dreamer (Self) acts at the moment as the percipient of dream. Neither can there be a (separate) .cogniser 【Within you】of the relation between the dreamer (the Self) and dream, nor a separate cognition 【Within you】of, that (relation) ; for then you would commit the fallacy of infinite regress (anavastha). _ If the relation between the dreamer (the Self) and the dream could be cognised, another cogniser【Within you】 should be supposed to exist; then another cogniser of that cogniser ; ,then another of that again; and so on; and thus the series would necessarily be endless.
Simply put, the dreamer can know the dream, but at the same time cannot know that he is dreaming. If we say that someone else within him cognises that he is dreaming, then we enter an infinite regression. Why your analogy of son-mother fails is because the son is at the same level of reality as the mother, while the relation of maya-Self is like the dream-dreamer relation.
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