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The Undifferentiated Tao is represented in this system as a point or a bindu mark as it is sometimes known.
It is yin and yang in perfect balance. Nirvana. All concepts are merely fragments of the whole, the Tao. It cannot be percieved by the physical senses which deal soley with the Material, nor in the absolute sense can it be known by the intellect which is a dualistic tool and deals only with parts and conceptual fragments which it sorts and catagorises in accordance with its limited knowledge.
The Tao transcends catagory, there is nothing for the intellect to grasp onto.
Of course the essence of a human being is much more than mere intellect and so the Tao can be Realized by Realizing that True part of ones own nature.