Acharya Prashant explains that desire is born from the union of stubbornness and falsehood. Stubbornness is the persistent and irrational insistence on one's own incompleteness, which creates a void that seeks external fulfillment. The speaker describes this stubbornness as the mother of desire and the lie as its father. The lie consists of claiming that an external object has fulfilled the self, even though the world is incapable of providing such completion. This deception is maintained to protect the ego, which is not a factual reality but a stubborn insistence on its own existence.