Acharya Prashant explains that the ego's nature is to perceive everything through its own filters of desire, self-interest, and conditioning. He demonstrates this through an exercise where different people associate the same words with different personal meanings, proving that our thoughts are merely extensions of our internal world. He emphasizes that Truth is 'Achintya' (inconceivable), meaning it cannot be grasped by thought, imagination, or emotion. Anything that can be thought of or visualized is limited by the ego and cannot provide liberation. Therefore, the Upanishads describe Truth through negation, systematically stripping away all mental projections like form, color, and gender to prevent the mind from creating a false image of the divine.