The discussion centers on the philosophical inquiry into whether 'existence' is a concept or an actual state, and whether a brain is necessary to conceptualize or actualize an external world. Participants explore the idea that while the universe does not exist solely because it is being experienced, consciousness is required for that experience. The conversation touches on the implications of materialism versus idealism, with some arguing that concepts like unicorns exist as mental constructs rather than physical entities. The debate also references the Copenhagen Interpretation of quantum mechanics, suggesting that the universe may not exist in a definite state until observed, raising questions about the nature of observation and consciousness. Ultimately, the dialogue considers whether something can exist independently of human perception, with examples like trees and rocks supporting the notion of pre-existing entities.