purnamadah: 'That is complete.'
purnamidam: 'This is complete.'
purnamadah purnamidam 'That is complete, this is complete'.
purnat purna mudachyate - 'From that completeness comes this completeness'
purnasya purnamadaya - If we take away this completeness from that completeness'
purnameva vashishyate: 'Only completeness remains.'

purnamadah purnamidam, the beginning is the Supreme Reality.
Described in the Upanishad as the Supreme Brahman, Para Brahman, The Ultimate Truth.
"That Supreme Reality is Complete'. It is purna, It is always full, complete and self-existing,
Permanent, The Supreme Reality remains when everything else perishes.
That Supreme Reality which knows no darkness but only effulgence.
Free of impurities and imperfections. It is complete and full.

What then is Supreme Brahman?
Purnamidam: 'This is also Complete.'
'That Supreme Truth is complete' and 'This is complete'
The Supreme Truth is not outside of yourself "All this is Brahman. All is Truth."
But, The Truth is veiled. You remove the veil, and all differences disappear .
Then "This Brahman ' becomes no different from 'That Brahman.'

The spiritual aspect of "This and That" differentiation, is caused by the separation in the mind.
'That is Complete, This is Complete.' Purnameva vashishyate- even if we are separating,
'That remains complete and purna.' It is the ultimate, of absolute unity - That, that is One.

The physical aspect is the sum total of energy. Energy can neither be created nor destroyed. It's form can change to another, but it will not disappear, because "It" remains constant. The deeper aspects of the Upanishad, this energy in all human beings is inactive. The process of sadhana, understanding and imbibing the Vedas is when this energy is awakened.

This energy till it is inactive, is potential energy. This energy does all the work of reproduction and growth. The whole growing-up of the organism, is done by this energy. And after it has done all its work, it descends to a psychic location coils up, and becomes inactive. Nothing is reduced from it but is is dormant, remains forever as it was. It is converted into active energy through the process of raising the Kundalini. The coiled power that sits at the tail of the spine. It remains ready to be awakened by the proper person, at the proper time.