Material Energy: Material Conditioning

Q. 1. I'm wondering how individual free will factors into the verses and purports describing the species of demoniac life. Specifically BG 16.19 - 20.

Srila Prabhupada's purport states:
"In this verse it is clearly indicated that the placing of a Particular individual soul in a particular body is the prerogative of the supreme will."

"As for the demoniac, it is clearly said here that they are perpetually put into the wombs of demons, and thus they continue to be envious, the lowest of mankind."

Q. Will there be always some souls for in this material world or will there be a moment in eternity when there won't be any material world. For I heard that for the ompleteness of Lord Krishna there is need for material world.