Acharya Prashant explains that all mental activity is defined as thought. He posits that the world we perceive is essentially a thought because it is only accessible to us through our senses and mental processing. Since the world is perceived through the mind, it exists within the mind. He argues that objects like a wall have no existence beyond the sensory inputs of sight and touch; therefore, the world is mental. He clarifies that even scientific knowledge or ignorance enters through the senses, leading sages to conclude that the world is an illusion or 'Mithya'. He further explains that the body itself is a mental construct, as its existence is only known through sensory perception. Acharya Prashant states that the entire universe is a thought, and both the external and internal spaces are divisions created within the mind. He emphasizes that the search for absolute reality cannot happen within the world because the world is mental. Instead, one must turn to meditation to find that which is not mental. He notes that the universe and the ego (Ahamkar) are interconnected; they arise and dissolve together. When one realizes the universe is a thought, they also realize that the one who perceives it is part of that same illusion. Finally, he discusses how different beings inhabit different universes based on their mental states. He clarifies that it is not just a matter of different perspectives on an objective reality, but that the objects themselves are thoughts. He defines truth or absolute reality as that which is independent and unchanging. Since the world changes based on the state of the observer, it is considered 'Mithya'. He concludes that if the observer's brain or consciousness changes significantly, the perceived world can change entirely or even disappear.